e787644caf
When the CPU goes idle for the last time during the CPU down hotplug
process, RCU reports a final quiescent state for the current CPU. If
this quiescent state propagates up to the top, some tasks may then be
woken up to complete the grace period: the main grace period kthread
and/or the expedited main workqueue (or kworker).
If those kthreads have a SCHED_FIFO policy, the wake up can indirectly
arm the RT bandwith timer to the local offline CPU. Since this happens
after hrtimers have been migrated at CPUHP_AP_HRTIMERS_DYING stage, the
timer gets ignored. Therefore if the RCU kthreads are waiting for RT
bandwidth to be available, they may never be actually scheduled.
This triggers TREE03 rcutorture hangs:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 4-...!: (1 GPs behind) idle=9874/1/0x4000000000000000 softirq=0/0 fqs=20 rcuc=21071 jiffies(starved)
rcu: (t=21035 jiffies g=938281 q=40787 ncpus=6)
rcu: rcu_preempt kthread starved for 20964 jiffies! g938281 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:R running task stack:14896 pid:14 tgid:14 ppid:2 flags:0x00004000
Call Trace:
<TASK>
__schedule+0x2eb/0xa80
schedule+0x1f/0x90
schedule_timeout+0x163/0x270
? __pfx_process_timeout+0x10/0x10
rcu_gp_fqs_loop+0x37c/0x5b0
? __pfx_rcu_gp_kthread+0x10/0x10
rcu_gp_kthread+0x17c/0x200
kthread+0xde/0x110
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2b/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1b/0x30
</TASK>
The situation can't be solved with just unpinning the timer. The hrtimer
infrastructure and the nohz heuristics involved in finding the best
remote target for an unpinned timer would then also need to handle
enqueues from an offline CPU in the most horrendous way.
So fix this on the RCU side instead and defer the wake up to an online
CPU if it's too late for the local one.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Fixes: 5c0930ccaa
("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
5174 lines
168 KiB
C
5174 lines
168 KiB
C
// SPDX-License-Identifier: GPL-2.0+
|
||
/*
|
||
* Read-Copy Update mechanism for mutual exclusion (tree-based version)
|
||
*
|
||
* Copyright IBM Corporation, 2008
|
||
*
|
||
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
|
||
* Manfred Spraul <manfred@colorfullife.com>
|
||
* Paul E. McKenney <paulmck@linux.ibm.com>
|
||
*
|
||
* Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
|
||
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
|
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*
|
||
* For detailed explanation of Read-Copy Update mechanism see -
|
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* Documentation/RCU
|
||
*/
|
||
|
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#define pr_fmt(fmt) "rcu: " fmt
|
||
|
||
#include <linux/types.h>
|
||
#include <linux/kernel.h>
|
||
#include <linux/init.h>
|
||
#include <linux/spinlock.h>
|
||
#include <linux/smp.h>
|
||
#include <linux/rcupdate_wait.h>
|
||
#include <linux/interrupt.h>
|
||
#include <linux/sched.h>
|
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#include <linux/sched/debug.h>
|
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#include <linux/nmi.h>
|
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#include <linux/atomic.h>
|
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#include <linux/bitops.h>
|
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#include <linux/export.h>
|
||
#include <linux/completion.h>
|
||
#include <linux/kmemleak.h>
|
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#include <linux/moduleparam.h>
|
||
#include <linux/panic.h>
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#include <linux/panic_notifier.h>
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#include <linux/percpu.h>
|
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#include <linux/notifier.h>
|
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#include <linux/cpu.h>
|
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#include <linux/mutex.h>
|
||
#include <linux/time.h>
|
||
#include <linux/kernel_stat.h>
|
||
#include <linux/wait.h>
|
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#include <linux/kthread.h>
|
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#include <uapi/linux/sched/types.h>
|
||
#include <linux/prefetch.h>
|
||
#include <linux/delay.h>
|
||
#include <linux/random.h>
|
||
#include <linux/trace_events.h>
|
||
#include <linux/suspend.h>
|
||
#include <linux/ftrace.h>
|
||
#include <linux/tick.h>
|
||
#include <linux/sysrq.h>
|
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#include <linux/kprobes.h>
|
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#include <linux/gfp.h>
|
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#include <linux/oom.h>
|
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#include <linux/smpboot.h>
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#include <linux/jiffies.h>
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#include <linux/slab.h>
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#include <linux/sched/isolation.h>
|
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#include <linux/sched/clock.h>
|
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#include <linux/vmalloc.h>
|
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#include <linux/mm.h>
|
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#include <linux/kasan.h>
|
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#include <linux/context_tracking.h>
|
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#include "../time/tick-internal.h"
|
||
|
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#include "tree.h"
|
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#include "rcu.h"
|
||
|
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#ifdef MODULE_PARAM_PREFIX
|
||
#undef MODULE_PARAM_PREFIX
|
||
#endif
|
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#define MODULE_PARAM_PREFIX "rcutree."
|
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|
||
/* Data structures. */
|
||
|
||
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
|
||
.gpwrap = true,
|
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#ifdef CONFIG_RCU_NOCB_CPU
|
||
.cblist.flags = SEGCBLIST_RCU_CORE,
|
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#endif
|
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};
|
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static struct rcu_state rcu_state = {
|
||
.level = { &rcu_state.node[0] },
|
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.gp_state = RCU_GP_IDLE,
|
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.gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT,
|
||
.barrier_mutex = __MUTEX_INITIALIZER(rcu_state.barrier_mutex),
|
||
.barrier_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.barrier_lock),
|
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.name = RCU_NAME,
|
||
.abbr = RCU_ABBR,
|
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.exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex),
|
||
.exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex),
|
||
.ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED,
|
||
};
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||
|
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/* Dump rcu_node combining tree at boot to verify correct setup. */
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static bool dump_tree;
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module_param(dump_tree, bool, 0444);
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/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */
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static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT);
|
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#ifndef CONFIG_PREEMPT_RT
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module_param(use_softirq, bool, 0444);
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#endif
|
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/* Control rcu_node-tree auto-balancing at boot time. */
|
||
static bool rcu_fanout_exact;
|
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module_param(rcu_fanout_exact, bool, 0444);
|
||
/* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */
|
||
static int rcu_fanout_leaf = RCU_FANOUT_LEAF;
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module_param(rcu_fanout_leaf, int, 0444);
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int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
|
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/* Number of rcu_nodes at specified level. */
|
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int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
|
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int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
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||
|
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/*
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* The rcu_scheduler_active variable is initialized to the value
|
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* RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the
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* first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE,
|
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* RCU can assume that there is but one task, allowing RCU to (for example)
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* optimize synchronize_rcu() to a simple barrier(). When this variable
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* is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required
|
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* to detect real grace periods. This variable is also used to suppress
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* boot-time false positives from lockdep-RCU error checking. Finally, it
|
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* transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU
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* is fully initialized, including all of its kthreads having been spawned.
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*/
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int rcu_scheduler_active __read_mostly;
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EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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/*
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* The rcu_scheduler_fully_active variable transitions from zero to one
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* during the early_initcall() processing, which is after the scheduler
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* is capable of creating new tasks. So RCU processing (for example,
|
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* creating tasks for RCU priority boosting) must be delayed until after
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* rcu_scheduler_fully_active transitions from zero to one. We also
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* currently delay invocation of any RCU callbacks until after this point.
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*
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* It might later prove better for people registering RCU callbacks during
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* early boot to take responsibility for these callbacks, but one step at
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* a time.
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*/
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static int rcu_scheduler_fully_active __read_mostly;
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static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
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unsigned long gps, unsigned long flags);
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static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
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static void invoke_rcu_core(void);
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static void rcu_report_exp_rdp(struct rcu_data *rdp);
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static void sync_sched_exp_online_cleanup(int cpu);
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static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
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static bool rcu_rdp_is_offloaded(struct rcu_data *rdp);
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static bool rcu_rdp_cpu_online(struct rcu_data *rdp);
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static bool rcu_init_invoked(void);
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static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
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static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
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/*
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* rcuc/rcub/rcuop kthread realtime priority. The "rcuop"
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* real-time priority(enabling/disabling) is controlled by
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* the extra CONFIG_RCU_NOCB_CPU_CB_BOOST configuration.
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*/
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static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
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module_param(kthread_prio, int, 0444);
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/* Delay in jiffies for grace-period initialization delays, debug only. */
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static int gp_preinit_delay;
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module_param(gp_preinit_delay, int, 0444);
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static int gp_init_delay;
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module_param(gp_init_delay, int, 0444);
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static int gp_cleanup_delay;
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module_param(gp_cleanup_delay, int, 0444);
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|
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// Add delay to rcu_read_unlock() for strict grace periods.
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static int rcu_unlock_delay;
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#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD
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module_param(rcu_unlock_delay, int, 0444);
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#endif
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|
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/*
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* This rcu parameter is runtime-read-only. It reflects
|
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* a minimum allowed number of objects which can be cached
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* per-CPU. Object size is equal to one page. This value
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* can be changed at boot time.
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*/
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static int rcu_min_cached_objs = 5;
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module_param(rcu_min_cached_objs, int, 0444);
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|
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// A page shrinker can ask for pages to be freed to make them
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// available for other parts of the system. This usually happens
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// under low memory conditions, and in that case we should also
|
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// defer page-cache filling for a short time period.
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//
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// The default value is 5 seconds, which is long enough to reduce
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// interference with the shrinker while it asks other systems to
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// drain their caches.
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static int rcu_delay_page_cache_fill_msec = 5000;
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module_param(rcu_delay_page_cache_fill_msec, int, 0444);
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|
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/* Retrieve RCU kthreads priority for rcutorture */
|
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int rcu_get_gp_kthreads_prio(void)
|
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{
|
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return kthread_prio;
|
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}
|
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EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio);
|
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|
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/*
|
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* Number of grace periods between delays, normalized by the duration of
|
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* the delay. The longer the delay, the more the grace periods between
|
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* each delay. The reason for this normalization is that it means that,
|
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* for non-zero delays, the overall slowdown of grace periods is constant
|
||
* regardless of the duration of the delay. This arrangement balances
|
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* the need for long delays to increase some race probabilities with the
|
||
* need for fast grace periods to increase other race probabilities.
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*/
|
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#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays for debugging. */
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||
|
||
/*
|
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* Return true if an RCU grace period is in progress. The READ_ONCE()s
|
||
* permit this function to be invoked without holding the root rcu_node
|
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* structure's ->lock, but of course results can be subject to change.
|
||
*/
|
||
static int rcu_gp_in_progress(void)
|
||
{
|
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return rcu_seq_state(rcu_seq_current(&rcu_state.gp_seq));
|
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}
|
||
|
||
/*
|
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* Return the number of callbacks queued on the specified CPU.
|
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* Handles both the nocbs and normal cases.
|
||
*/
|
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static long rcu_get_n_cbs_cpu(int cpu)
|
||
{
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
if (rcu_segcblist_is_enabled(&rdp->cblist))
|
||
return rcu_segcblist_n_cbs(&rdp->cblist);
|
||
return 0;
|
||
}
|
||
|
||
void rcu_softirq_qs(void)
|
||
{
|
||
rcu_qs();
|
||
rcu_preempt_deferred_qs(current);
|
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rcu_tasks_qs(current, false);
|
||
}
|
||
|
||
/*
|
||
* Reset the current CPU's ->dynticks counter to indicate that the
|
||
* newly onlined CPU is no longer in an extended quiescent state.
|
||
* This will either leave the counter unchanged, or increment it
|
||
* to the next non-quiescent value.
|
||
*
|
||
* The non-atomic test/increment sequence works because the upper bits
|
||
* of the ->dynticks counter are manipulated only by the corresponding CPU,
|
||
* or when the corresponding CPU is offline.
|
||
*/
|
||
static void rcu_dynticks_eqs_online(void)
|
||
{
|
||
if (ct_dynticks() & RCU_DYNTICKS_IDX)
|
||
return;
|
||
ct_state_inc(RCU_DYNTICKS_IDX);
|
||
}
|
||
|
||
/*
|
||
* Snapshot the ->dynticks counter with full ordering so as to allow
|
||
* stable comparison of this counter with past and future snapshots.
|
||
*/
|
||
static int rcu_dynticks_snap(int cpu)
|
||
{
|
||
smp_mb(); // Fundamental RCU ordering guarantee.
|
||
return ct_dynticks_cpu_acquire(cpu);
|
||
}
|
||
|
||
/*
|
||
* Return true if the snapshot returned from rcu_dynticks_snap()
|
||
* indicates that RCU is in an extended quiescent state.
|
||
*/
|
||
static bool rcu_dynticks_in_eqs(int snap)
|
||
{
|
||
return !(snap & RCU_DYNTICKS_IDX);
|
||
}
|
||
|
||
/*
|
||
* Return true if the CPU corresponding to the specified rcu_data
|
||
* structure has spent some time in an extended quiescent state since
|
||
* rcu_dynticks_snap() returned the specified snapshot.
|
||
*/
|
||
static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
|
||
{
|
||
return snap != rcu_dynticks_snap(rdp->cpu);
|
||
}
|
||
|
||
/*
|
||
* Return true if the referenced integer is zero while the specified
|
||
* CPU remains within a single extended quiescent state.
|
||
*/
|
||
bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
|
||
{
|
||
int snap;
|
||
|
||
// If not quiescent, force back to earlier extended quiescent state.
|
||
snap = ct_dynticks_cpu(cpu) & ~RCU_DYNTICKS_IDX;
|
||
smp_rmb(); // Order ->dynticks and *vp reads.
|
||
if (READ_ONCE(*vp))
|
||
return false; // Non-zero, so report failure;
|
||
smp_rmb(); // Order *vp read and ->dynticks re-read.
|
||
|
||
// If still in the same extended quiescent state, we are good!
|
||
return snap == ct_dynticks_cpu(cpu);
|
||
}
|
||
|
||
/*
|
||
* Let the RCU core know that this CPU has gone through the scheduler,
|
||
* which is a quiescent state. This is called when the need for a
|
||
* quiescent state is urgent, so we burn an atomic operation and full
|
||
* memory barriers to let the RCU core know about it, regardless of what
|
||
* this CPU might (or might not) do in the near future.
|
||
*
|
||
* We inform the RCU core by emulating a zero-duration dyntick-idle period.
|
||
*
|
||
* The caller must have disabled interrupts and must not be idle.
|
||
*/
|
||
notrace void rcu_momentary_dyntick_idle(void)
|
||
{
|
||
int seq;
|
||
|
||
raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
|
||
seq = ct_state_inc(2 * RCU_DYNTICKS_IDX);
|
||
/* It is illegal to call this from idle state. */
|
||
WARN_ON_ONCE(!(seq & RCU_DYNTICKS_IDX));
|
||
rcu_preempt_deferred_qs(current);
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
|
||
|
||
/**
|
||
* rcu_is_cpu_rrupt_from_idle - see if 'interrupted' from idle
|
||
*
|
||
* If the current CPU is idle and running at a first-level (not nested)
|
||
* interrupt, or directly, from idle, return true.
|
||
*
|
||
* The caller must have at least disabled IRQs.
|
||
*/
|
||
static int rcu_is_cpu_rrupt_from_idle(void)
|
||
{
|
||
long nesting;
|
||
|
||
/*
|
||
* Usually called from the tick; but also used from smp_function_call()
|
||
* for expedited grace periods. This latter can result in running from
|
||
* the idle task, instead of an actual IPI.
|
||
*/
|
||
lockdep_assert_irqs_disabled();
|
||
|
||
/* Check for counter underflows */
|
||
RCU_LOCKDEP_WARN(ct_dynticks_nesting() < 0,
|
||
"RCU dynticks_nesting counter underflow!");
|
||
RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() <= 0,
|
||
"RCU dynticks_nmi_nesting counter underflow/zero!");
|
||
|
||
/* Are we at first interrupt nesting level? */
|
||
nesting = ct_dynticks_nmi_nesting();
|
||
if (nesting > 1)
|
||
return false;
|
||
|
||
/*
|
||
* If we're not in an interrupt, we must be in the idle task!
|
||
*/
|
||
WARN_ON_ONCE(!nesting && !is_idle_task(current));
|
||
|
||
/* Does CPU appear to be idle from an RCU standpoint? */
|
||
return ct_dynticks_nesting() == 0;
|
||
}
|
||
|
||
#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
|
||
// Maximum callbacks per rcu_do_batch ...
|
||
#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood.
|
||
static long blimit = DEFAULT_RCU_BLIMIT;
|
||
#define DEFAULT_RCU_QHIMARK 10000 // If this many pending, ignore blimit.
|
||
static long qhimark = DEFAULT_RCU_QHIMARK;
|
||
#define DEFAULT_RCU_QLOMARK 100 // Once only this many pending, use blimit.
|
||
static long qlowmark = DEFAULT_RCU_QLOMARK;
|
||
#define DEFAULT_RCU_QOVLD_MULT 2
|
||
#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK)
|
||
static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS.
|
||
static long qovld_calc = -1; // No pre-initialization lock acquisitions!
|
||
|
||
module_param(blimit, long, 0444);
|
||
module_param(qhimark, long, 0444);
|
||
module_param(qlowmark, long, 0444);
|
||
module_param(qovld, long, 0444);
|
||
|
||
static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX;
|
||
static ulong jiffies_till_next_fqs = ULONG_MAX;
|
||
static bool rcu_kick_kthreads;
|
||
static int rcu_divisor = 7;
|
||
module_param(rcu_divisor, int, 0644);
|
||
|
||
/* Force an exit from rcu_do_batch() after 3 milliseconds. */
|
||
static long rcu_resched_ns = 3 * NSEC_PER_MSEC;
|
||
module_param(rcu_resched_ns, long, 0644);
|
||
|
||
/*
|
||
* How long the grace period must be before we start recruiting
|
||
* quiescent-state help from rcu_note_context_switch().
|
||
*/
|
||
static ulong jiffies_till_sched_qs = ULONG_MAX;
|
||
module_param(jiffies_till_sched_qs, ulong, 0444);
|
||
static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */
|
||
module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */
|
||
|
||
/*
|
||
* Make sure that we give the grace-period kthread time to detect any
|
||
* idle CPUs before taking active measures to force quiescent states.
|
||
* However, don't go below 100 milliseconds, adjusted upwards for really
|
||
* large systems.
|
||
*/
|
||
static void adjust_jiffies_till_sched_qs(void)
|
||
{
|
||
unsigned long j;
|
||
|
||
/* If jiffies_till_sched_qs was specified, respect the request. */
|
||
if (jiffies_till_sched_qs != ULONG_MAX) {
|
||
WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs);
|
||
return;
|
||
}
|
||
/* Otherwise, set to third fqs scan, but bound below on large system. */
|
||
j = READ_ONCE(jiffies_till_first_fqs) +
|
||
2 * READ_ONCE(jiffies_till_next_fqs);
|
||
if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV)
|
||
j = HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
|
||
pr_info("RCU calculated value of scheduler-enlistment delay is %ld jiffies.\n", j);
|
||
WRITE_ONCE(jiffies_to_sched_qs, j);
|
||
}
|
||
|
||
static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp)
|
||
{
|
||
ulong j;
|
||
int ret = kstrtoul(val, 0, &j);
|
||
|
||
if (!ret) {
|
||
WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j);
|
||
adjust_jiffies_till_sched_qs();
|
||
}
|
||
return ret;
|
||
}
|
||
|
||
static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp)
|
||
{
|
||
ulong j;
|
||
int ret = kstrtoul(val, 0, &j);
|
||
|
||
if (!ret) {
|
||
WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1));
|
||
adjust_jiffies_till_sched_qs();
|
||
}
|
||
return ret;
|
||
}
|
||
|
||
static const struct kernel_param_ops first_fqs_jiffies_ops = {
|
||
.set = param_set_first_fqs_jiffies,
|
||
.get = param_get_ulong,
|
||
};
|
||
|
||
static const struct kernel_param_ops next_fqs_jiffies_ops = {
|
||
.set = param_set_next_fqs_jiffies,
|
||
.get = param_get_ulong,
|
||
};
|
||
|
||
module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644);
|
||
module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644);
|
||
module_param(rcu_kick_kthreads, bool, 0644);
|
||
|
||
static void force_qs_rnp(int (*f)(struct rcu_data *rdp));
|
||
static int rcu_pending(int user);
|
||
|
||
/*
|
||
* Return the number of RCU GPs completed thus far for debug & stats.
|
||
*/
|
||
unsigned long rcu_get_gp_seq(void)
|
||
{
|
||
return READ_ONCE(rcu_state.gp_seq);
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_get_gp_seq);
|
||
|
||
/*
|
||
* Return the number of RCU expedited batches completed thus far for
|
||
* debug & stats. Odd numbers mean that a batch is in progress, even
|
||
* numbers mean idle. The value returned will thus be roughly double
|
||
* the cumulative batches since boot.
|
||
*/
|
||
unsigned long rcu_exp_batches_completed(void)
|
||
{
|
||
return rcu_state.expedited_sequence;
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
|
||
|
||
/*
|
||
* Return the root node of the rcu_state structure.
|
||
*/
|
||
static struct rcu_node *rcu_get_root(void)
|
||
{
|
||
return &rcu_state.node[0];
|
||
}
|
||
|
||
/*
|
||
* Send along grace-period-related data for rcutorture diagnostics.
|
||
*/
|
||
void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
|
||
unsigned long *gp_seq)
|
||
{
|
||
switch (test_type) {
|
||
case RCU_FLAVOR:
|
||
*flags = READ_ONCE(rcu_state.gp_flags);
|
||
*gp_seq = rcu_seq_current(&rcu_state.gp_seq);
|
||
break;
|
||
default:
|
||
break;
|
||
}
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
|
||
|
||
#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
|
||
/*
|
||
* An empty function that will trigger a reschedule on
|
||
* IRQ tail once IRQs get re-enabled on userspace/guest resume.
|
||
*/
|
||
static void late_wakeup_func(struct irq_work *work)
|
||
{
|
||
}
|
||
|
||
static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) =
|
||
IRQ_WORK_INIT(late_wakeup_func);
|
||
|
||
/*
|
||
* If either:
|
||
*
|
||
* 1) the task is about to enter in guest mode and $ARCH doesn't support KVM generic work
|
||
* 2) the task is about to enter in user mode and $ARCH doesn't support generic entry.
|
||
*
|
||
* In these cases the late RCU wake ups aren't supported in the resched loops and our
|
||
* last resort is to fire a local irq_work that will trigger a reschedule once IRQs
|
||
* get re-enabled again.
|
||
*/
|
||
noinstr void rcu_irq_work_resched(void)
|
||
{
|
||
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
||
|
||
if (IS_ENABLED(CONFIG_GENERIC_ENTRY) && !(current->flags & PF_VCPU))
|
||
return;
|
||
|
||
if (IS_ENABLED(CONFIG_KVM_XFER_TO_GUEST_WORK) && (current->flags & PF_VCPU))
|
||
return;
|
||
|
||
instrumentation_begin();
|
||
if (do_nocb_deferred_wakeup(rdp) && need_resched()) {
|
||
irq_work_queue(this_cpu_ptr(&late_wakeup_work));
|
||
}
|
||
instrumentation_end();
|
||
}
|
||
#endif /* #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) */
|
||
|
||
#ifdef CONFIG_PROVE_RCU
|
||
/**
|
||
* rcu_irq_exit_check_preempt - Validate that scheduling is possible
|
||
*/
|
||
void rcu_irq_exit_check_preempt(void)
|
||
{
|
||
lockdep_assert_irqs_disabled();
|
||
|
||
RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
|
||
"RCU dynticks_nesting counter underflow/zero!");
|
||
RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() !=
|
||
DYNTICK_IRQ_NONIDLE,
|
||
"Bad RCU dynticks_nmi_nesting counter\n");
|
||
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
|
||
"RCU in extended quiescent state!");
|
||
}
|
||
#endif /* #ifdef CONFIG_PROVE_RCU */
|
||
|
||
#ifdef CONFIG_NO_HZ_FULL
|
||
/**
|
||
* __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it.
|
||
*
|
||
* The scheduler tick is not normally enabled when CPUs enter the kernel
|
||
* from nohz_full userspace execution. After all, nohz_full userspace
|
||
* execution is an RCU quiescent state and the time executing in the kernel
|
||
* is quite short. Except of course when it isn't. And it is not hard to
|
||
* cause a large system to spend tens of seconds or even minutes looping
|
||
* in the kernel, which can cause a number of problems, include RCU CPU
|
||
* stall warnings.
|
||
*
|
||
* Therefore, if a nohz_full CPU fails to report a quiescent state
|
||
* in a timely manner, the RCU grace-period kthread sets that CPU's
|
||
* ->rcu_urgent_qs flag with the expectation that the next interrupt or
|
||
* exception will invoke this function, which will turn on the scheduler
|
||
* tick, which will enable RCU to detect that CPU's quiescent states,
|
||
* for example, due to cond_resched() calls in CONFIG_PREEMPT=n kernels.
|
||
* The tick will be disabled once a quiescent state is reported for
|
||
* this CPU.
|
||
*
|
||
* Of course, in carefully tuned systems, there might never be an
|
||
* interrupt or exception. In that case, the RCU grace-period kthread
|
||
* will eventually cause one to happen. However, in less carefully
|
||
* controlled environments, this function allows RCU to get what it
|
||
* needs without creating otherwise useless interruptions.
|
||
*/
|
||
void __rcu_irq_enter_check_tick(void)
|
||
{
|
||
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
||
|
||
// If we're here from NMI there's nothing to do.
|
||
if (in_nmi())
|
||
return;
|
||
|
||
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
|
||
"Illegal rcu_irq_enter_check_tick() from extended quiescent state");
|
||
|
||
if (!tick_nohz_full_cpu(rdp->cpu) ||
|
||
!READ_ONCE(rdp->rcu_urgent_qs) ||
|
||
READ_ONCE(rdp->rcu_forced_tick)) {
|
||
// RCU doesn't need nohz_full help from this CPU, or it is
|
||
// already getting that help.
|
||
return;
|
||
}
|
||
|
||
// We get here only when not in an extended quiescent state and
|
||
// from interrupts (as opposed to NMIs). Therefore, (1) RCU is
|
||
// already watching and (2) The fact that we are in an interrupt
|
||
// handler and that the rcu_node lock is an irq-disabled lock
|
||
// prevents self-deadlock. So we can safely recheck under the lock.
|
||
// Note that the nohz_full state currently cannot change.
|
||
raw_spin_lock_rcu_node(rdp->mynode);
|
||
if (READ_ONCE(rdp->rcu_urgent_qs) && !rdp->rcu_forced_tick) {
|
||
// A nohz_full CPU is in the kernel and RCU needs a
|
||
// quiescent state. Turn on the tick!
|
||
WRITE_ONCE(rdp->rcu_forced_tick, true);
|
||
tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
|
||
}
|
||
raw_spin_unlock_rcu_node(rdp->mynode);
|
||
}
|
||
NOKPROBE_SYMBOL(__rcu_irq_enter_check_tick);
|
||
#endif /* CONFIG_NO_HZ_FULL */
|
||
|
||
/*
|
||
* Check to see if any future non-offloaded RCU-related work will need
|
||
* to be done by the current CPU, even if none need be done immediately,
|
||
* returning 1 if so. This function is part of the RCU implementation;
|
||
* it is -not- an exported member of the RCU API. This is used by
|
||
* the idle-entry code to figure out whether it is safe to disable the
|
||
* scheduler-clock interrupt.
|
||
*
|
||
* Just check whether or not this CPU has non-offloaded RCU callbacks
|
||
* queued.
|
||
*/
|
||
int rcu_needs_cpu(void)
|
||
{
|
||
return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist) &&
|
||
!rcu_rdp_is_offloaded(this_cpu_ptr(&rcu_data));
|
||
}
|
||
|
||
/*
|
||
* If any sort of urgency was applied to the current CPU (for example,
|
||
* the scheduler-clock interrupt was enabled on a nohz_full CPU) in order
|
||
* to get to a quiescent state, disable it.
|
||
*/
|
||
static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
|
||
{
|
||
raw_lockdep_assert_held_rcu_node(rdp->mynode);
|
||
WRITE_ONCE(rdp->rcu_urgent_qs, false);
|
||
WRITE_ONCE(rdp->rcu_need_heavy_qs, false);
|
||
if (tick_nohz_full_cpu(rdp->cpu) && rdp->rcu_forced_tick) {
|
||
tick_dep_clear_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
|
||
WRITE_ONCE(rdp->rcu_forced_tick, false);
|
||
}
|
||
}
|
||
|
||
/**
|
||
* rcu_is_watching - RCU read-side critical sections permitted on current CPU?
|
||
*
|
||
* Return @true if RCU is watching the running CPU and @false otherwise.
|
||
* An @true return means that this CPU can safely enter RCU read-side
|
||
* critical sections.
|
||
*
|
||
* Although calls to rcu_is_watching() from most parts of the kernel
|
||
* will return @true, there are important exceptions. For example, if the
|
||
* current CPU is deep within its idle loop, in kernel entry/exit code,
|
||
* or offline, rcu_is_watching() will return @false.
|
||
*
|
||
* Make notrace because it can be called by the internal functions of
|
||
* ftrace, and making this notrace removes unnecessary recursion calls.
|
||
*/
|
||
notrace bool rcu_is_watching(void)
|
||
{
|
||
bool ret;
|
||
|
||
preempt_disable_notrace();
|
||
ret = !rcu_dynticks_curr_cpu_in_eqs();
|
||
preempt_enable_notrace();
|
||
return ret;
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_is_watching);
|
||
|
||
/*
|
||
* If a holdout task is actually running, request an urgent quiescent
|
||
* state from its CPU. This is unsynchronized, so migrations can cause
|
||
* the request to go to the wrong CPU. Which is OK, all that will happen
|
||
* is that the CPU's next context switch will be a bit slower and next
|
||
* time around this task will generate another request.
|
||
*/
|
||
void rcu_request_urgent_qs_task(struct task_struct *t)
|
||
{
|
||
int cpu;
|
||
|
||
barrier();
|
||
cpu = task_cpu(t);
|
||
if (!task_curr(t))
|
||
return; /* This task is not running on that CPU. */
|
||
smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true);
|
||
}
|
||
|
||
/*
|
||
* When trying to report a quiescent state on behalf of some other CPU,
|
||
* it is our responsibility to check for and handle potential overflow
|
||
* of the rcu_node ->gp_seq counter with respect to the rcu_data counters.
|
||
* After all, the CPU might be in deep idle state, and thus executing no
|
||
* code whatsoever.
|
||
*/
|
||
static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp)
|
||
{
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4,
|
||
rnp->gp_seq))
|
||
WRITE_ONCE(rdp->gpwrap, true);
|
||
if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq))
|
||
rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4;
|
||
}
|
||
|
||
/*
|
||
* Snapshot the specified CPU's dynticks counter so that we can later
|
||
* credit them with an implicit quiescent state. Return 1 if this CPU
|
||
* is in dynticks idle mode, which is an extended quiescent state.
|
||
*/
|
||
static int dyntick_save_progress_counter(struct rcu_data *rdp)
|
||
{
|
||
rdp->dynticks_snap = rcu_dynticks_snap(rdp->cpu);
|
||
if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) {
|
||
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
|
||
rcu_gpnum_ovf(rdp->mynode, rdp);
|
||
return 1;
|
||
}
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Returns positive if the specified CPU has passed through a quiescent state
|
||
* by virtue of being in or having passed through an dynticks idle state since
|
||
* the last call to dyntick_save_progress_counter() for this same CPU, or by
|
||
* virtue of having been offline.
|
||
*
|
||
* Returns negative if the specified CPU needs a force resched.
|
||
*
|
||
* Returns zero otherwise.
|
||
*/
|
||
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
|
||
{
|
||
unsigned long jtsq;
|
||
int ret = 0;
|
||
struct rcu_node *rnp = rdp->mynode;
|
||
|
||
/*
|
||
* If the CPU passed through or entered a dynticks idle phase with
|
||
* no active irq/NMI handlers, then we can safely pretend that the CPU
|
||
* already acknowledged the request to pass through a quiescent
|
||
* state. Either way, that CPU cannot possibly be in an RCU
|
||
* read-side critical section that started before the beginning
|
||
* of the current RCU grace period.
|
||
*/
|
||
if (rcu_dynticks_in_eqs_since(rdp, rdp->dynticks_snap)) {
|
||
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
|
||
rcu_gpnum_ovf(rnp, rdp);
|
||
return 1;
|
||
}
|
||
|
||
/*
|
||
* Complain if a CPU that is considered to be offline from RCU's
|
||
* perspective has not yet reported a quiescent state. After all,
|
||
* the offline CPU should have reported a quiescent state during
|
||
* the CPU-offline process, or, failing that, by rcu_gp_init()
|
||
* if it ran concurrently with either the CPU going offline or the
|
||
* last task on a leaf rcu_node structure exiting its RCU read-side
|
||
* critical section while all CPUs corresponding to that structure
|
||
* are offline. This added warning detects bugs in any of these
|
||
* code paths.
|
||
*
|
||
* The rcu_node structure's ->lock is held here, which excludes
|
||
* the relevant portions the CPU-hotplug code, the grace-period
|
||
* initialization code, and the rcu_read_unlock() code paths.
|
||
*
|
||
* For more detail, please refer to the "Hotplug CPU" section
|
||
* of RCU's Requirements documentation.
|
||
*/
|
||
if (WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp))) {
|
||
struct rcu_node *rnp1;
|
||
|
||
pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
|
||
__func__, rnp->grplo, rnp->grphi, rnp->level,
|
||
(long)rnp->gp_seq, (long)rnp->completedqs);
|
||
for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)
|
||
pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n",
|
||
__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask);
|
||
pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n",
|
||
__func__, rdp->cpu, ".o"[rcu_rdp_cpu_online(rdp)],
|
||
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
|
||
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
|
||
return 1; /* Break things loose after complaining. */
|
||
}
|
||
|
||
/*
|
||
* A CPU running for an extended time within the kernel can
|
||
* delay RCU grace periods: (1) At age jiffies_to_sched_qs,
|
||
* set .rcu_urgent_qs, (2) At age 2*jiffies_to_sched_qs, set
|
||
* both .rcu_need_heavy_qs and .rcu_urgent_qs. Note that the
|
||
* unsynchronized assignments to the per-CPU rcu_need_heavy_qs
|
||
* variable are safe because the assignments are repeated if this
|
||
* CPU failed to pass through a quiescent state. This code
|
||
* also checks .jiffies_resched in case jiffies_to_sched_qs
|
||
* is set way high.
|
||
*/
|
||
jtsq = READ_ONCE(jiffies_to_sched_qs);
|
||
if (!READ_ONCE(rdp->rcu_need_heavy_qs) &&
|
||
(time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
|
||
time_after(jiffies, rcu_state.jiffies_resched) ||
|
||
rcu_state.cbovld)) {
|
||
WRITE_ONCE(rdp->rcu_need_heavy_qs, true);
|
||
/* Store rcu_need_heavy_qs before rcu_urgent_qs. */
|
||
smp_store_release(&rdp->rcu_urgent_qs, true);
|
||
} else if (time_after(jiffies, rcu_state.gp_start + jtsq)) {
|
||
WRITE_ONCE(rdp->rcu_urgent_qs, true);
|
||
}
|
||
|
||
/*
|
||
* NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq!
|
||
* The above code handles this, but only for straight cond_resched().
|
||
* And some in-kernel loops check need_resched() before calling
|
||
* cond_resched(), which defeats the above code for CPUs that are
|
||
* running in-kernel with scheduling-clock interrupts disabled.
|
||
* So hit them over the head with the resched_cpu() hammer!
|
||
*/
|
||
if (tick_nohz_full_cpu(rdp->cpu) &&
|
||
(time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) ||
|
||
rcu_state.cbovld)) {
|
||
WRITE_ONCE(rdp->rcu_urgent_qs, true);
|
||
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
|
||
ret = -1;
|
||
}
|
||
|
||
/*
|
||
* If more than halfway to RCU CPU stall-warning time, invoke
|
||
* resched_cpu() more frequently to try to loosen things up a bit.
|
||
* Also check to see if the CPU is getting hammered with interrupts,
|
||
* but only once per grace period, just to keep the IPIs down to
|
||
* a dull roar.
|
||
*/
|
||
if (time_after(jiffies, rcu_state.jiffies_resched)) {
|
||
if (time_after(jiffies,
|
||
READ_ONCE(rdp->last_fqs_resched) + jtsq)) {
|
||
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
|
||
ret = -1;
|
||
}
|
||
if (IS_ENABLED(CONFIG_IRQ_WORK) &&
|
||
!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&
|
||
(rnp->ffmask & rdp->grpmask)) {
|
||
rdp->rcu_iw_pending = true;
|
||
rdp->rcu_iw_gp_seq = rnp->gp_seq;
|
||
irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
|
||
}
|
||
|
||
if (rcu_cpu_stall_cputime && rdp->snap_record.gp_seq != rdp->gp_seq) {
|
||
int cpu = rdp->cpu;
|
||
struct rcu_snap_record *rsrp;
|
||
struct kernel_cpustat *kcsp;
|
||
|
||
kcsp = &kcpustat_cpu(cpu);
|
||
|
||
rsrp = &rdp->snap_record;
|
||
rsrp->cputime_irq = kcpustat_field(kcsp, CPUTIME_IRQ, cpu);
|
||
rsrp->cputime_softirq = kcpustat_field(kcsp, CPUTIME_SOFTIRQ, cpu);
|
||
rsrp->cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
|
||
rsrp->nr_hardirqs = kstat_cpu_irqs_sum(rdp->cpu);
|
||
rsrp->nr_softirqs = kstat_cpu_softirqs_sum(rdp->cpu);
|
||
rsrp->nr_csw = nr_context_switches_cpu(rdp->cpu);
|
||
rsrp->jiffies = jiffies;
|
||
rsrp->gp_seq = rdp->gp_seq;
|
||
}
|
||
}
|
||
|
||
return ret;
|
||
}
|
||
|
||
/* Trace-event wrapper function for trace_rcu_future_grace_period. */
|
||
static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
|
||
unsigned long gp_seq_req, const char *s)
|
||
{
|
||
trace_rcu_future_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
|
||
gp_seq_req, rnp->level,
|
||
rnp->grplo, rnp->grphi, s);
|
||
}
|
||
|
||
/*
|
||
* rcu_start_this_gp - Request the start of a particular grace period
|
||
* @rnp_start: The leaf node of the CPU from which to start.
|
||
* @rdp: The rcu_data corresponding to the CPU from which to start.
|
||
* @gp_seq_req: The gp_seq of the grace period to start.
|
||
*
|
||
* Start the specified grace period, as needed to handle newly arrived
|
||
* callbacks. The required future grace periods are recorded in each
|
||
* rcu_node structure's ->gp_seq_needed field. Returns true if there
|
||
* is reason to awaken the grace-period kthread.
|
||
*
|
||
* The caller must hold the specified rcu_node structure's ->lock, which
|
||
* is why the caller is responsible for waking the grace-period kthread.
|
||
*
|
||
* Returns true if the GP thread needs to be awakened else false.
|
||
*/
|
||
static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
|
||
unsigned long gp_seq_req)
|
||
{
|
||
bool ret = false;
|
||
struct rcu_node *rnp;
|
||
|
||
/*
|
||
* Use funnel locking to either acquire the root rcu_node
|
||
* structure's lock or bail out if the need for this grace period
|
||
* has already been recorded -- or if that grace period has in
|
||
* fact already started. If there is already a grace period in
|
||
* progress in a non-leaf node, no recording is needed because the
|
||
* end of the grace period will scan the leaf rcu_node structures.
|
||
* Note that rnp_start->lock must not be released.
|
||
*/
|
||
raw_lockdep_assert_held_rcu_node(rnp_start);
|
||
trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startleaf"));
|
||
for (rnp = rnp_start; 1; rnp = rnp->parent) {
|
||
if (rnp != rnp_start)
|
||
raw_spin_lock_rcu_node(rnp);
|
||
if (ULONG_CMP_GE(rnp->gp_seq_needed, gp_seq_req) ||
|
||
rcu_seq_started(&rnp->gp_seq, gp_seq_req) ||
|
||
(rnp != rnp_start &&
|
||
rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))) {
|
||
trace_rcu_this_gp(rnp, rdp, gp_seq_req,
|
||
TPS("Prestarted"));
|
||
goto unlock_out;
|
||
}
|
||
WRITE_ONCE(rnp->gp_seq_needed, gp_seq_req);
|
||
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) {
|
||
/*
|
||
* We just marked the leaf or internal node, and a
|
||
* grace period is in progress, which means that
|
||
* rcu_gp_cleanup() will see the marking. Bail to
|
||
* reduce contention.
|
||
*/
|
||
trace_rcu_this_gp(rnp_start, rdp, gp_seq_req,
|
||
TPS("Startedleaf"));
|
||
goto unlock_out;
|
||
}
|
||
if (rnp != rnp_start && rnp->parent != NULL)
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
if (!rnp->parent)
|
||
break; /* At root, and perhaps also leaf. */
|
||
}
|
||
|
||
/* If GP already in progress, just leave, otherwise start one. */
|
||
if (rcu_gp_in_progress()) {
|
||
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedleafroot"));
|
||
goto unlock_out;
|
||
}
|
||
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot"));
|
||
WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT);
|
||
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
|
||
if (!READ_ONCE(rcu_state.gp_kthread)) {
|
||
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread"));
|
||
goto unlock_out;
|
||
}
|
||
trace_rcu_grace_period(rcu_state.name, data_race(rcu_state.gp_seq), TPS("newreq"));
|
||
ret = true; /* Caller must wake GP kthread. */
|
||
unlock_out:
|
||
/* Push furthest requested GP to leaf node and rcu_data structure. */
|
||
if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) {
|
||
WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed);
|
||
WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
|
||
}
|
||
if (rnp != rnp_start)
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
return ret;
|
||
}
|
||
|
||
/*
|
||
* Clean up any old requests for the just-ended grace period. Also return
|
||
* whether any additional grace periods have been requested.
|
||
*/
|
||
static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
|
||
{
|
||
bool needmore;
|
||
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
||
|
||
needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed);
|
||
if (!needmore)
|
||
rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */
|
||
trace_rcu_this_gp(rnp, rdp, rnp->gp_seq,
|
||
needmore ? TPS("CleanupMore") : TPS("Cleanup"));
|
||
return needmore;
|
||
}
|
||
|
||
static void swake_up_one_online_ipi(void *arg)
|
||
{
|
||
struct swait_queue_head *wqh = arg;
|
||
|
||
swake_up_one(wqh);
|
||
}
|
||
|
||
static void swake_up_one_online(struct swait_queue_head *wqh)
|
||
{
|
||
int cpu = get_cpu();
|
||
|
||
/*
|
||
* If called from rcutree_report_cpu_starting(), wake up
|
||
* is dangerous that late in the CPU-down hotplug process. The
|
||
* scheduler might queue an ignored hrtimer. Defer the wake up
|
||
* to an online CPU instead.
|
||
*/
|
||
if (unlikely(cpu_is_offline(cpu))) {
|
||
int target;
|
||
|
||
target = cpumask_any_and(housekeeping_cpumask(HK_TYPE_RCU),
|
||
cpu_online_mask);
|
||
|
||
smp_call_function_single(target, swake_up_one_online_ipi,
|
||
wqh, 0);
|
||
put_cpu();
|
||
} else {
|
||
put_cpu();
|
||
swake_up_one(wqh);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Awaken the grace-period kthread. Don't do a self-awaken (unless in an
|
||
* interrupt or softirq handler, in which case we just might immediately
|
||
* sleep upon return, resulting in a grace-period hang), and don't bother
|
||
* awakening when there is nothing for the grace-period kthread to do
|
||
* (as in several CPUs raced to awaken, we lost), and finally don't try
|
||
* to awaken a kthread that has not yet been created. If all those checks
|
||
* are passed, track some debug information and awaken.
|
||
*
|
||
* So why do the self-wakeup when in an interrupt or softirq handler
|
||
* in the grace-period kthread's context? Because the kthread might have
|
||
* been interrupted just as it was going to sleep, and just after the final
|
||
* pre-sleep check of the awaken condition. In this case, a wakeup really
|
||
* is required, and is therefore supplied.
|
||
*/
|
||
static void rcu_gp_kthread_wake(void)
|
||
{
|
||
struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);
|
||
|
||
if ((current == t && !in_hardirq() && !in_serving_softirq()) ||
|
||
!READ_ONCE(rcu_state.gp_flags) || !t)
|
||
return;
|
||
WRITE_ONCE(rcu_state.gp_wake_time, jiffies);
|
||
WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq));
|
||
swake_up_one_online(&rcu_state.gp_wq);
|
||
}
|
||
|
||
/*
|
||
* If there is room, assign a ->gp_seq number to any callbacks on this
|
||
* CPU that have not already been assigned. Also accelerate any callbacks
|
||
* that were previously assigned a ->gp_seq number that has since proven
|
||
* to be too conservative, which can happen if callbacks get assigned a
|
||
* ->gp_seq number while RCU is idle, but with reference to a non-root
|
||
* rcu_node structure. This function is idempotent, so it does not hurt
|
||
* to call it repeatedly. Returns an flag saying that we should awaken
|
||
* the RCU grace-period kthread.
|
||
*
|
||
* The caller must hold rnp->lock with interrupts disabled.
|
||
*/
|
||
static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
|
||
{
|
||
unsigned long gp_seq_req;
|
||
bool ret = false;
|
||
|
||
rcu_lockdep_assert_cblist_protected(rdp);
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
|
||
/* If no pending (not yet ready to invoke) callbacks, nothing to do. */
|
||
if (!rcu_segcblist_pend_cbs(&rdp->cblist))
|
||
return false;
|
||
|
||
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPreAcc"));
|
||
|
||
/*
|
||
* Callbacks are often registered with incomplete grace-period
|
||
* information. Something about the fact that getting exact
|
||
* information requires acquiring a global lock... RCU therefore
|
||
* makes a conservative estimate of the grace period number at which
|
||
* a given callback will become ready to invoke. The following
|
||
* code checks this estimate and improves it when possible, thus
|
||
* accelerating callback invocation to an earlier grace-period
|
||
* number.
|
||
*/
|
||
gp_seq_req = rcu_seq_snap(&rcu_state.gp_seq);
|
||
if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req))
|
||
ret = rcu_start_this_gp(rnp, rdp, gp_seq_req);
|
||
|
||
/* Trace depending on how much we were able to accelerate. */
|
||
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
|
||
trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccWaitCB"));
|
||
else
|
||
trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB"));
|
||
|
||
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPostAcc"));
|
||
|
||
return ret;
|
||
}
|
||
|
||
/*
|
||
* Similar to rcu_accelerate_cbs(), but does not require that the leaf
|
||
* rcu_node structure's ->lock be held. It consults the cached value
|
||
* of ->gp_seq_needed in the rcu_data structure, and if that indicates
|
||
* that a new grace-period request be made, invokes rcu_accelerate_cbs()
|
||
* while holding the leaf rcu_node structure's ->lock.
|
||
*/
|
||
static void rcu_accelerate_cbs_unlocked(struct rcu_node *rnp,
|
||
struct rcu_data *rdp)
|
||
{
|
||
unsigned long c;
|
||
bool needwake;
|
||
|
||
rcu_lockdep_assert_cblist_protected(rdp);
|
||
c = rcu_seq_snap(&rcu_state.gp_seq);
|
||
if (!READ_ONCE(rdp->gpwrap) && ULONG_CMP_GE(rdp->gp_seq_needed, c)) {
|
||
/* Old request still live, so mark recent callbacks. */
|
||
(void)rcu_segcblist_accelerate(&rdp->cblist, c);
|
||
return;
|
||
}
|
||
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
|
||
needwake = rcu_accelerate_cbs(rnp, rdp);
|
||
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
||
if (needwake)
|
||
rcu_gp_kthread_wake();
|
||
}
|
||
|
||
/*
|
||
* Move any callbacks whose grace period has completed to the
|
||
* RCU_DONE_TAIL sublist, then compact the remaining sublists and
|
||
* assign ->gp_seq numbers to any callbacks in the RCU_NEXT_TAIL
|
||
* sublist. This function is idempotent, so it does not hurt to
|
||
* invoke it repeatedly. As long as it is not invoked -too- often...
|
||
* Returns true if the RCU grace-period kthread needs to be awakened.
|
||
*
|
||
* The caller must hold rnp->lock with interrupts disabled.
|
||
*/
|
||
static bool rcu_advance_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
|
||
{
|
||
rcu_lockdep_assert_cblist_protected(rdp);
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
|
||
/* If no pending (not yet ready to invoke) callbacks, nothing to do. */
|
||
if (!rcu_segcblist_pend_cbs(&rdp->cblist))
|
||
return false;
|
||
|
||
/*
|
||
* Find all callbacks whose ->gp_seq numbers indicate that they
|
||
* are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
|
||
*/
|
||
rcu_segcblist_advance(&rdp->cblist, rnp->gp_seq);
|
||
|
||
/* Classify any remaining callbacks. */
|
||
return rcu_accelerate_cbs(rnp, rdp);
|
||
}
|
||
|
||
/*
|
||
* Move and classify callbacks, but only if doing so won't require
|
||
* that the RCU grace-period kthread be awakened.
|
||
*/
|
||
static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp,
|
||
struct rcu_data *rdp)
|
||
{
|
||
rcu_lockdep_assert_cblist_protected(rdp);
|
||
if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || !raw_spin_trylock_rcu_node(rnp))
|
||
return;
|
||
// The grace period cannot end while we hold the rcu_node lock.
|
||
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))
|
||
WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp));
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
}
|
||
|
||
/*
|
||
* In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, attempt to generate a
|
||
* quiescent state. This is intended to be invoked when the CPU notices
|
||
* a new grace period.
|
||
*/
|
||
static void rcu_strict_gp_check_qs(void)
|
||
{
|
||
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
|
||
rcu_read_lock();
|
||
rcu_read_unlock();
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Update CPU-local rcu_data state to record the beginnings and ends of
|
||
* grace periods. The caller must hold the ->lock of the leaf rcu_node
|
||
* structure corresponding to the current CPU, and must have irqs disabled.
|
||
* Returns true if the grace-period kthread needs to be awakened.
|
||
*/
|
||
static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
|
||
{
|
||
bool ret = false;
|
||
bool need_qs;
|
||
const bool offloaded = rcu_rdp_is_offloaded(rdp);
|
||
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
|
||
if (rdp->gp_seq == rnp->gp_seq)
|
||
return false; /* Nothing to do. */
|
||
|
||
/* Handle the ends of any preceding grace periods first. */
|
||
if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) ||
|
||
unlikely(READ_ONCE(rdp->gpwrap))) {
|
||
if (!offloaded)
|
||
ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */
|
||
rdp->core_needs_qs = false;
|
||
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend"));
|
||
} else {
|
||
if (!offloaded)
|
||
ret = rcu_accelerate_cbs(rnp, rdp); /* Recent CBs. */
|
||
if (rdp->core_needs_qs)
|
||
rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);
|
||
}
|
||
|
||
/* Now handle the beginnings of any new-to-this-CPU grace periods. */
|
||
if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) ||
|
||
unlikely(READ_ONCE(rdp->gpwrap))) {
|
||
/*
|
||
* If the current grace period is waiting for this CPU,
|
||
* set up to detect a quiescent state, otherwise don't
|
||
* go looking for one.
|
||
*/
|
||
trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, TPS("cpustart"));
|
||
need_qs = !!(rnp->qsmask & rdp->grpmask);
|
||
rdp->cpu_no_qs.b.norm = need_qs;
|
||
rdp->core_needs_qs = need_qs;
|
||
zero_cpu_stall_ticks(rdp);
|
||
}
|
||
rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */
|
||
if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap)
|
||
WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
|
||
if (IS_ENABLED(CONFIG_PROVE_RCU) && READ_ONCE(rdp->gpwrap))
|
||
WRITE_ONCE(rdp->last_sched_clock, jiffies);
|
||
WRITE_ONCE(rdp->gpwrap, false);
|
||
rcu_gpnum_ovf(rnp, rdp);
|
||
return ret;
|
||
}
|
||
|
||
static void note_gp_changes(struct rcu_data *rdp)
|
||
{
|
||
unsigned long flags;
|
||
bool needwake;
|
||
struct rcu_node *rnp;
|
||
|
||
local_irq_save(flags);
|
||
rnp = rdp->mynode;
|
||
if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) &&
|
||
!unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */
|
||
!raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */
|
||
local_irq_restore(flags);
|
||
return;
|
||
}
|
||
needwake = __note_gp_changes(rnp, rdp);
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
rcu_strict_gp_check_qs();
|
||
if (needwake)
|
||
rcu_gp_kthread_wake();
|
||
}
|
||
|
||
static atomic_t *rcu_gp_slow_suppress;
|
||
|
||
/* Register a counter to suppress debugging grace-period delays. */
|
||
void rcu_gp_slow_register(atomic_t *rgssp)
|
||
{
|
||
WARN_ON_ONCE(rcu_gp_slow_suppress);
|
||
|
||
WRITE_ONCE(rcu_gp_slow_suppress, rgssp);
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_gp_slow_register);
|
||
|
||
/* Unregister a counter, with NULL for not caring which. */
|
||
void rcu_gp_slow_unregister(atomic_t *rgssp)
|
||
{
|
||
WARN_ON_ONCE(rgssp && rgssp != rcu_gp_slow_suppress && rcu_gp_slow_suppress != NULL);
|
||
|
||
WRITE_ONCE(rcu_gp_slow_suppress, NULL);
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_gp_slow_unregister);
|
||
|
||
static bool rcu_gp_slow_is_suppressed(void)
|
||
{
|
||
atomic_t *rgssp = READ_ONCE(rcu_gp_slow_suppress);
|
||
|
||
return rgssp && atomic_read(rgssp);
|
||
}
|
||
|
||
static void rcu_gp_slow(int delay)
|
||
{
|
||
if (!rcu_gp_slow_is_suppressed() && delay > 0 &&
|
||
!(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
|
||
schedule_timeout_idle(delay);
|
||
}
|
||
|
||
static unsigned long sleep_duration;
|
||
|
||
/* Allow rcutorture to stall the grace-period kthread. */
|
||
void rcu_gp_set_torture_wait(int duration)
|
||
{
|
||
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST) && duration > 0)
|
||
WRITE_ONCE(sleep_duration, duration);
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_gp_set_torture_wait);
|
||
|
||
/* Actually implement the aforementioned wait. */
|
||
static void rcu_gp_torture_wait(void)
|
||
{
|
||
unsigned long duration;
|
||
|
||
if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST))
|
||
return;
|
||
duration = xchg(&sleep_duration, 0UL);
|
||
if (duration > 0) {
|
||
pr_alert("%s: Waiting %lu jiffies\n", __func__, duration);
|
||
schedule_timeout_idle(duration);
|
||
pr_alert("%s: Wait complete\n", __func__);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Handler for on_each_cpu() to invoke the target CPU's RCU core
|
||
* processing.
|
||
*/
|
||
static void rcu_strict_gp_boundary(void *unused)
|
||
{
|
||
invoke_rcu_core();
|
||
}
|
||
|
||
// Make the polled API aware of the beginning of a grace period.
|
||
static void rcu_poll_gp_seq_start(unsigned long *snap)
|
||
{
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
|
||
// If RCU was idle, note beginning of GP.
|
||
if (!rcu_seq_state(rcu_state.gp_seq_polled))
|
||
rcu_seq_start(&rcu_state.gp_seq_polled);
|
||
|
||
// Either way, record current state.
|
||
*snap = rcu_state.gp_seq_polled;
|
||
}
|
||
|
||
// Make the polled API aware of the end of a grace period.
|
||
static void rcu_poll_gp_seq_end(unsigned long *snap)
|
||
{
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
|
||
// If the previously noted GP is still in effect, record the
|
||
// end of that GP. Either way, zero counter to avoid counter-wrap
|
||
// problems.
|
||
if (*snap && *snap == rcu_state.gp_seq_polled) {
|
||
rcu_seq_end(&rcu_state.gp_seq_polled);
|
||
rcu_state.gp_seq_polled_snap = 0;
|
||
rcu_state.gp_seq_polled_exp_snap = 0;
|
||
} else {
|
||
*snap = 0;
|
||
}
|
||
}
|
||
|
||
// Make the polled API aware of the beginning of a grace period, but
|
||
// where caller does not hold the root rcu_node structure's lock.
|
||
static void rcu_poll_gp_seq_start_unlocked(unsigned long *snap)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
if (rcu_init_invoked()) {
|
||
if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
|
||
lockdep_assert_irqs_enabled();
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
}
|
||
rcu_poll_gp_seq_start(snap);
|
||
if (rcu_init_invoked())
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
}
|
||
|
||
// Make the polled API aware of the end of a grace period, but where
|
||
// caller does not hold the root rcu_node structure's lock.
|
||
static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
if (rcu_init_invoked()) {
|
||
if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
|
||
lockdep_assert_irqs_enabled();
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
}
|
||
rcu_poll_gp_seq_end(snap);
|
||
if (rcu_init_invoked())
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
}
|
||
|
||
/*
|
||
* Initialize a new grace period. Return false if no grace period required.
|
||
*/
|
||
static noinline_for_stack bool rcu_gp_init(void)
|
||
{
|
||
unsigned long flags;
|
||
unsigned long oldmask;
|
||
unsigned long mask;
|
||
struct rcu_data *rdp;
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
raw_spin_lock_irq_rcu_node(rnp);
|
||
if (!READ_ONCE(rcu_state.gp_flags)) {
|
||
/* Spurious wakeup, tell caller to go back to sleep. */
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
return false;
|
||
}
|
||
WRITE_ONCE(rcu_state.gp_flags, 0); /* Clear all flags: New GP. */
|
||
|
||
if (WARN_ON_ONCE(rcu_gp_in_progress())) {
|
||
/*
|
||
* Grace period already in progress, don't start another.
|
||
* Not supposed to be able to happen.
|
||
*/
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
return false;
|
||
}
|
||
|
||
/* Advance to a new grace period and initialize state. */
|
||
record_gp_stall_check_time();
|
||
/* Record GP times before starting GP, hence rcu_seq_start(). */
|
||
rcu_seq_start(&rcu_state.gp_seq);
|
||
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start"));
|
||
rcu_poll_gp_seq_start(&rcu_state.gp_seq_polled_snap);
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
|
||
/*
|
||
* Apply per-leaf buffered online and offline operations to
|
||
* the rcu_node tree. Note that this new grace period need not
|
||
* wait for subsequent online CPUs, and that RCU hooks in the CPU
|
||
* offlining path, when combined with checks in this function,
|
||
* will handle CPUs that are currently going offline or that will
|
||
* go offline later. Please also refer to "Hotplug CPU" section
|
||
* of RCU's Requirements documentation.
|
||
*/
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_ONOFF);
|
||
/* Exclude CPU hotplug operations. */
|
||
rcu_for_each_leaf_node(rnp) {
|
||
local_irq_save(flags);
|
||
arch_spin_lock(&rcu_state.ofl_lock);
|
||
raw_spin_lock_rcu_node(rnp);
|
||
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
|
||
!rnp->wait_blkd_tasks) {
|
||
/* Nothing to do on this leaf rcu_node structure. */
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
arch_spin_unlock(&rcu_state.ofl_lock);
|
||
local_irq_restore(flags);
|
||
continue;
|
||
}
|
||
|
||
/* Record old state, apply changes to ->qsmaskinit field. */
|
||
oldmask = rnp->qsmaskinit;
|
||
rnp->qsmaskinit = rnp->qsmaskinitnext;
|
||
|
||
/* If zero-ness of ->qsmaskinit changed, propagate up tree. */
|
||
if (!oldmask != !rnp->qsmaskinit) {
|
||
if (!oldmask) { /* First online CPU for rcu_node. */
|
||
if (!rnp->wait_blkd_tasks) /* Ever offline? */
|
||
rcu_init_new_rnp(rnp);
|
||
} else if (rcu_preempt_has_tasks(rnp)) {
|
||
rnp->wait_blkd_tasks = true; /* blocked tasks */
|
||
} else { /* Last offline CPU and can propagate. */
|
||
rcu_cleanup_dead_rnp(rnp);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* If all waited-on tasks from prior grace period are
|
||
* done, and if all this rcu_node structure's CPUs are
|
||
* still offline, propagate up the rcu_node tree and
|
||
* clear ->wait_blkd_tasks. Otherwise, if one of this
|
||
* rcu_node structure's CPUs has since come back online,
|
||
* simply clear ->wait_blkd_tasks.
|
||
*/
|
||
if (rnp->wait_blkd_tasks &&
|
||
(!rcu_preempt_has_tasks(rnp) || rnp->qsmaskinit)) {
|
||
rnp->wait_blkd_tasks = false;
|
||
if (!rnp->qsmaskinit)
|
||
rcu_cleanup_dead_rnp(rnp);
|
||
}
|
||
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
arch_spin_unlock(&rcu_state.ofl_lock);
|
||
local_irq_restore(flags);
|
||
}
|
||
rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */
|
||
|
||
/*
|
||
* Set the quiescent-state-needed bits in all the rcu_node
|
||
* structures for all currently online CPUs in breadth-first
|
||
* order, starting from the root rcu_node structure, relying on the
|
||
* layout of the tree within the rcu_state.node[] array. Note that
|
||
* other CPUs will access only the leaves of the hierarchy, thus
|
||
* seeing that no grace period is in progress, at least until the
|
||
* corresponding leaf node has been initialized.
|
||
*
|
||
* The grace period cannot complete until the initialization
|
||
* process finishes, because this kthread handles both.
|
||
*/
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_INIT);
|
||
rcu_for_each_node_breadth_first(rnp) {
|
||
rcu_gp_slow(gp_init_delay);
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
rdp = this_cpu_ptr(&rcu_data);
|
||
rcu_preempt_check_blocked_tasks(rnp);
|
||
rnp->qsmask = rnp->qsmaskinit;
|
||
WRITE_ONCE(rnp->gp_seq, rcu_state.gp_seq);
|
||
if (rnp == rdp->mynode)
|
||
(void)__note_gp_changes(rnp, rdp);
|
||
rcu_preempt_boost_start_gp(rnp);
|
||
trace_rcu_grace_period_init(rcu_state.name, rnp->gp_seq,
|
||
rnp->level, rnp->grplo,
|
||
rnp->grphi, rnp->qsmask);
|
||
/* Quiescent states for tasks on any now-offline CPUs. */
|
||
mask = rnp->qsmask & ~rnp->qsmaskinitnext;
|
||
rnp->rcu_gp_init_mask = mask;
|
||
if ((mask || rnp->wait_blkd_tasks) && rcu_is_leaf_node(rnp))
|
||
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
||
else
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
cond_resched_tasks_rcu_qs();
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
}
|
||
|
||
// If strict, make all CPUs aware of new grace period.
|
||
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
|
||
on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
|
||
|
||
return true;
|
||
}
|
||
|
||
/*
|
||
* Helper function for swait_event_idle_exclusive() wakeup at force-quiescent-state
|
||
* time.
|
||
*/
|
||
static bool rcu_gp_fqs_check_wake(int *gfp)
|
||
{
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
// If under overload conditions, force an immediate FQS scan.
|
||
if (*gfp & RCU_GP_FLAG_OVLD)
|
||
return true;
|
||
|
||
// Someone like call_rcu() requested a force-quiescent-state scan.
|
||
*gfp = READ_ONCE(rcu_state.gp_flags);
|
||
if (*gfp & RCU_GP_FLAG_FQS)
|
||
return true;
|
||
|
||
// The current grace period has completed.
|
||
if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp))
|
||
return true;
|
||
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* Do one round of quiescent-state forcing.
|
||
*/
|
||
static void rcu_gp_fqs(bool first_time)
|
||
{
|
||
int nr_fqs = READ_ONCE(rcu_state.nr_fqs_jiffies_stall);
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
WRITE_ONCE(rcu_state.n_force_qs, rcu_state.n_force_qs + 1);
|
||
|
||
WARN_ON_ONCE(nr_fqs > 3);
|
||
/* Only countdown nr_fqs for stall purposes if jiffies moves. */
|
||
if (nr_fqs) {
|
||
if (nr_fqs == 1) {
|
||
WRITE_ONCE(rcu_state.jiffies_stall,
|
||
jiffies + rcu_jiffies_till_stall_check());
|
||
}
|
||
WRITE_ONCE(rcu_state.nr_fqs_jiffies_stall, --nr_fqs);
|
||
}
|
||
|
||
if (first_time) {
|
||
/* Collect dyntick-idle snapshots. */
|
||
force_qs_rnp(dyntick_save_progress_counter);
|
||
} else {
|
||
/* Handle dyntick-idle and offline CPUs. */
|
||
force_qs_rnp(rcu_implicit_dynticks_qs);
|
||
}
|
||
/* Clear flag to prevent immediate re-entry. */
|
||
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) {
|
||
raw_spin_lock_irq_rcu_node(rnp);
|
||
WRITE_ONCE(rcu_state.gp_flags,
|
||
READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS);
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Loop doing repeated quiescent-state forcing until the grace period ends.
|
||
*/
|
||
static noinline_for_stack void rcu_gp_fqs_loop(void)
|
||
{
|
||
bool first_gp_fqs = true;
|
||
int gf = 0;
|
||
unsigned long j;
|
||
int ret;
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
j = READ_ONCE(jiffies_till_first_fqs);
|
||
if (rcu_state.cbovld)
|
||
gf = RCU_GP_FLAG_OVLD;
|
||
ret = 0;
|
||
for (;;) {
|
||
if (rcu_state.cbovld) {
|
||
j = (j + 2) / 3;
|
||
if (j <= 0)
|
||
j = 1;
|
||
}
|
||
if (!ret || time_before(jiffies + j, rcu_state.jiffies_force_qs)) {
|
||
WRITE_ONCE(rcu_state.jiffies_force_qs, jiffies + j);
|
||
/*
|
||
* jiffies_force_qs before RCU_GP_WAIT_FQS state
|
||
* update; required for stall checks.
|
||
*/
|
||
smp_wmb();
|
||
WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
|
||
jiffies + (j ? 3 * j : 2));
|
||
}
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
||
TPS("fqswait"));
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_FQS);
|
||
(void)swait_event_idle_timeout_exclusive(rcu_state.gp_wq,
|
||
rcu_gp_fqs_check_wake(&gf), j);
|
||
rcu_gp_torture_wait();
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS);
|
||
/* Locking provides needed memory barriers. */
|
||
/*
|
||
* Exit the loop if the root rcu_node structure indicates that the grace period
|
||
* has ended, leave the loop. The rcu_preempt_blocked_readers_cgp(rnp) check
|
||
* is required only for single-node rcu_node trees because readers blocking
|
||
* the current grace period are queued only on leaf rcu_node structures.
|
||
* For multi-node trees, checking the root node's ->qsmask suffices, because a
|
||
* given root node's ->qsmask bit is cleared only when all CPUs and tasks from
|
||
* the corresponding leaf nodes have passed through their quiescent state.
|
||
*/
|
||
if (!READ_ONCE(rnp->qsmask) &&
|
||
!rcu_preempt_blocked_readers_cgp(rnp))
|
||
break;
|
||
/* If time for quiescent-state forcing, do it. */
|
||
if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
|
||
(gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
||
TPS("fqsstart"));
|
||
rcu_gp_fqs(first_gp_fqs);
|
||
gf = 0;
|
||
if (first_gp_fqs) {
|
||
first_gp_fqs = false;
|
||
gf = rcu_state.cbovld ? RCU_GP_FLAG_OVLD : 0;
|
||
}
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
||
TPS("fqsend"));
|
||
cond_resched_tasks_rcu_qs();
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
ret = 0; /* Force full wait till next FQS. */
|
||
j = READ_ONCE(jiffies_till_next_fqs);
|
||
} else {
|
||
/* Deal with stray signal. */
|
||
cond_resched_tasks_rcu_qs();
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
WARN_ON(signal_pending(current));
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
||
TPS("fqswaitsig"));
|
||
ret = 1; /* Keep old FQS timing. */
|
||
j = jiffies;
|
||
if (time_after(jiffies, rcu_state.jiffies_force_qs))
|
||
j = 1;
|
||
else
|
||
j = rcu_state.jiffies_force_qs - j;
|
||
gf = 0;
|
||
}
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Clean up after the old grace period.
|
||
*/
|
||
static noinline void rcu_gp_cleanup(void)
|
||
{
|
||
int cpu;
|
||
bool needgp = false;
|
||
unsigned long gp_duration;
|
||
unsigned long new_gp_seq;
|
||
bool offloaded;
|
||
struct rcu_data *rdp;
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
struct swait_queue_head *sq;
|
||
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
raw_spin_lock_irq_rcu_node(rnp);
|
||
rcu_state.gp_end = jiffies;
|
||
gp_duration = rcu_state.gp_end - rcu_state.gp_start;
|
||
if (gp_duration > rcu_state.gp_max)
|
||
rcu_state.gp_max = gp_duration;
|
||
|
||
/*
|
||
* We know the grace period is complete, but to everyone else
|
||
* it appears to still be ongoing. But it is also the case
|
||
* that to everyone else it looks like there is nothing that
|
||
* they can do to advance the grace period. It is therefore
|
||
* safe for us to drop the lock in order to mark the grace
|
||
* period as completed in all of the rcu_node structures.
|
||
*/
|
||
rcu_poll_gp_seq_end(&rcu_state.gp_seq_polled_snap);
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
|
||
/*
|
||
* Propagate new ->gp_seq value to rcu_node structures so that
|
||
* other CPUs don't have to wait until the start of the next grace
|
||
* period to process their callbacks. This also avoids some nasty
|
||
* RCU grace-period initialization races by forcing the end of
|
||
* the current grace period to be completely recorded in all of
|
||
* the rcu_node structures before the beginning of the next grace
|
||
* period is recorded in any of the rcu_node structures.
|
||
*/
|
||
new_gp_seq = rcu_state.gp_seq;
|
||
rcu_seq_end(&new_gp_seq);
|
||
rcu_for_each_node_breadth_first(rnp) {
|
||
raw_spin_lock_irq_rcu_node(rnp);
|
||
if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)))
|
||
dump_blkd_tasks(rnp, 10);
|
||
WARN_ON_ONCE(rnp->qsmask);
|
||
WRITE_ONCE(rnp->gp_seq, new_gp_seq);
|
||
if (!rnp->parent)
|
||
smp_mb(); // Order against failing poll_state_synchronize_rcu_full().
|
||
rdp = this_cpu_ptr(&rcu_data);
|
||
if (rnp == rdp->mynode)
|
||
needgp = __note_gp_changes(rnp, rdp) || needgp;
|
||
/* smp_mb() provided by prior unlock-lock pair. */
|
||
needgp = rcu_future_gp_cleanup(rnp) || needgp;
|
||
// Reset overload indication for CPUs no longer overloaded
|
||
if (rcu_is_leaf_node(rnp))
|
||
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->cbovldmask) {
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
check_cb_ovld_locked(rdp, rnp);
|
||
}
|
||
sq = rcu_nocb_gp_get(rnp);
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
rcu_nocb_gp_cleanup(sq);
|
||
cond_resched_tasks_rcu_qs();
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
rcu_gp_slow(gp_cleanup_delay);
|
||
}
|
||
rnp = rcu_get_root();
|
||
raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */
|
||
|
||
/* Declare grace period done, trace first to use old GP number. */
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end"));
|
||
rcu_seq_end(&rcu_state.gp_seq);
|
||
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_IDLE);
|
||
/* Check for GP requests since above loop. */
|
||
rdp = this_cpu_ptr(&rcu_data);
|
||
if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) {
|
||
trace_rcu_this_gp(rnp, rdp, rnp->gp_seq_needed,
|
||
TPS("CleanupMore"));
|
||
needgp = true;
|
||
}
|
||
/* Advance CBs to reduce false positives below. */
|
||
offloaded = rcu_rdp_is_offloaded(rdp);
|
||
if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) {
|
||
|
||
// We get here if a grace period was needed (“needgp”)
|
||
// and the above call to rcu_accelerate_cbs() did not set
|
||
// the RCU_GP_FLAG_INIT bit in ->gp_state (which records
|
||
// the need for another grace period). The purpose
|
||
// of the “offloaded” check is to avoid invoking
|
||
// rcu_accelerate_cbs() on an offloaded CPU because we do not
|
||
// hold the ->nocb_lock needed to safely access an offloaded
|
||
// ->cblist. We do not want to acquire that lock because
|
||
// it can be heavily contended during callback floods.
|
||
|
||
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
|
||
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("newreq"));
|
||
} else {
|
||
|
||
// We get here either if there is no need for an
|
||
// additional grace period or if rcu_accelerate_cbs() has
|
||
// already set the RCU_GP_FLAG_INIT bit in ->gp_flags.
|
||
// So all we need to do is to clear all of the other
|
||
// ->gp_flags bits.
|
||
|
||
WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & RCU_GP_FLAG_INIT);
|
||
}
|
||
raw_spin_unlock_irq_rcu_node(rnp);
|
||
|
||
// If strict, make all CPUs aware of the end of the old grace period.
|
||
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
|
||
on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
|
||
}
|
||
|
||
/*
|
||
* Body of kthread that handles grace periods.
|
||
*/
|
||
static int __noreturn rcu_gp_kthread(void *unused)
|
||
{
|
||
rcu_bind_gp_kthread();
|
||
for (;;) {
|
||
|
||
/* Handle grace-period start. */
|
||
for (;;) {
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
||
TPS("reqwait"));
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_GPS);
|
||
swait_event_idle_exclusive(rcu_state.gp_wq,
|
||
READ_ONCE(rcu_state.gp_flags) &
|
||
RCU_GP_FLAG_INIT);
|
||
rcu_gp_torture_wait();
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DONE_GPS);
|
||
/* Locking provides needed memory barrier. */
|
||
if (rcu_gp_init())
|
||
break;
|
||
cond_resched_tasks_rcu_qs();
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
WARN_ON(signal_pending(current));
|
||
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
||
TPS("reqwaitsig"));
|
||
}
|
||
|
||
/* Handle quiescent-state forcing. */
|
||
rcu_gp_fqs_loop();
|
||
|
||
/* Handle grace-period end. */
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_CLEANUP);
|
||
rcu_gp_cleanup();
|
||
WRITE_ONCE(rcu_state.gp_state, RCU_GP_CLEANED);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Report a full set of quiescent states to the rcu_state data structure.
|
||
* Invoke rcu_gp_kthread_wake() to awaken the grace-period kthread if
|
||
* another grace period is required. Whether we wake the grace-period
|
||
* kthread or it awakens itself for the next round of quiescent-state
|
||
* forcing, that kthread will clean up after the just-completed grace
|
||
* period. Note that the caller must hold rnp->lock, which is released
|
||
* before return.
|
||
*/
|
||
static void rcu_report_qs_rsp(unsigned long flags)
|
||
__releases(rcu_get_root()->lock)
|
||
{
|
||
raw_lockdep_assert_held_rcu_node(rcu_get_root());
|
||
WARN_ON_ONCE(!rcu_gp_in_progress());
|
||
WRITE_ONCE(rcu_state.gp_flags,
|
||
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS);
|
||
raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags);
|
||
rcu_gp_kthread_wake();
|
||
}
|
||
|
||
/*
|
||
* Similar to rcu_report_qs_rdp(), for which it is a helper function.
|
||
* Allows quiescent states for a group of CPUs to be reported at one go
|
||
* to the specified rcu_node structure, though all the CPUs in the group
|
||
* must be represented by the same rcu_node structure (which need not be a
|
||
* leaf rcu_node structure, though it often will be). The gps parameter
|
||
* is the grace-period snapshot, which means that the quiescent states
|
||
* are valid only if rnp->gp_seq is equal to gps. That structure's lock
|
||
* must be held upon entry, and it is released before return.
|
||
*
|
||
* As a special case, if mask is zero, the bit-already-cleared check is
|
||
* disabled. This allows propagating quiescent state due to resumed tasks
|
||
* during grace-period initialization.
|
||
*/
|
||
static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
|
||
unsigned long gps, unsigned long flags)
|
||
__releases(rnp->lock)
|
||
{
|
||
unsigned long oldmask = 0;
|
||
struct rcu_node *rnp_c;
|
||
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
|
||
/* Walk up the rcu_node hierarchy. */
|
||
for (;;) {
|
||
if ((!(rnp->qsmask & mask) && mask) || rnp->gp_seq != gps) {
|
||
|
||
/*
|
||
* Our bit has already been cleared, or the
|
||
* relevant grace period is already over, so done.
|
||
*/
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
return;
|
||
}
|
||
WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
|
||
WARN_ON_ONCE(!rcu_is_leaf_node(rnp) &&
|
||
rcu_preempt_blocked_readers_cgp(rnp));
|
||
WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask);
|
||
trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq,
|
||
mask, rnp->qsmask, rnp->level,
|
||
rnp->grplo, rnp->grphi,
|
||
!!rnp->gp_tasks);
|
||
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
|
||
|
||
/* Other bits still set at this level, so done. */
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
return;
|
||
}
|
||
rnp->completedqs = rnp->gp_seq;
|
||
mask = rnp->grpmask;
|
||
if (rnp->parent == NULL) {
|
||
|
||
/* No more levels. Exit loop holding root lock. */
|
||
|
||
break;
|
||
}
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
rnp_c = rnp;
|
||
rnp = rnp->parent;
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
oldmask = READ_ONCE(rnp_c->qsmask);
|
||
}
|
||
|
||
/*
|
||
* Get here if we are the last CPU to pass through a quiescent
|
||
* state for this grace period. Invoke rcu_report_qs_rsp()
|
||
* to clean up and start the next grace period if one is needed.
|
||
*/
|
||
rcu_report_qs_rsp(flags); /* releases rnp->lock. */
|
||
}
|
||
|
||
/*
|
||
* Record a quiescent state for all tasks that were previously queued
|
||
* on the specified rcu_node structure and that were blocking the current
|
||
* RCU grace period. The caller must hold the corresponding rnp->lock with
|
||
* irqs disabled, and this lock is released upon return, but irqs remain
|
||
* disabled.
|
||
*/
|
||
static void __maybe_unused
|
||
rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
|
||
__releases(rnp->lock)
|
||
{
|
||
unsigned long gps;
|
||
unsigned long mask;
|
||
struct rcu_node *rnp_p;
|
||
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_RCU)) ||
|
||
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) ||
|
||
rnp->qsmask != 0) {
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
return; /* Still need more quiescent states! */
|
||
}
|
||
|
||
rnp->completedqs = rnp->gp_seq;
|
||
rnp_p = rnp->parent;
|
||
if (rnp_p == NULL) {
|
||
/*
|
||
* Only one rcu_node structure in the tree, so don't
|
||
* try to report up to its nonexistent parent!
|
||
*/
|
||
rcu_report_qs_rsp(flags);
|
||
return;
|
||
}
|
||
|
||
/* Report up the rest of the hierarchy, tracking current ->gp_seq. */
|
||
gps = rnp->gp_seq;
|
||
mask = rnp->grpmask;
|
||
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
||
raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */
|
||
rcu_report_qs_rnp(mask, rnp_p, gps, flags);
|
||
}
|
||
|
||
/*
|
||
* Record a quiescent state for the specified CPU to that CPU's rcu_data
|
||
* structure. This must be called from the specified CPU.
|
||
*/
|
||
static void
|
||
rcu_report_qs_rdp(struct rcu_data *rdp)
|
||
{
|
||
unsigned long flags;
|
||
unsigned long mask;
|
||
bool needacc = false;
|
||
struct rcu_node *rnp;
|
||
|
||
WARN_ON_ONCE(rdp->cpu != smp_processor_id());
|
||
rnp = rdp->mynode;
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq ||
|
||
rdp->gpwrap) {
|
||
|
||
/*
|
||
* The grace period in which this quiescent state was
|
||
* recorded has ended, so don't report it upwards.
|
||
* We will instead need a new quiescent state that lies
|
||
* within the current grace period.
|
||
*/
|
||
rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
return;
|
||
}
|
||
mask = rdp->grpmask;
|
||
rdp->core_needs_qs = false;
|
||
if ((rnp->qsmask & mask) == 0) {
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
} else {
|
||
/*
|
||
* This GP can't end until cpu checks in, so all of our
|
||
* callbacks can be processed during the next GP.
|
||
*
|
||
* NOCB kthreads have their own way to deal with that...
|
||
*/
|
||
if (!rcu_rdp_is_offloaded(rdp)) {
|
||
/*
|
||
* The current GP has not yet ended, so it
|
||
* should not be possible for rcu_accelerate_cbs()
|
||
* to return true. So complain, but don't awaken.
|
||
*/
|
||
WARN_ON_ONCE(rcu_accelerate_cbs(rnp, rdp));
|
||
} else if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
|
||
/*
|
||
* ...but NOCB kthreads may miss or delay callbacks acceleration
|
||
* if in the middle of a (de-)offloading process.
|
||
*/
|
||
needacc = true;
|
||
}
|
||
|
||
rcu_disable_urgency_upon_qs(rdp);
|
||
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
||
/* ^^^ Released rnp->lock */
|
||
|
||
if (needacc) {
|
||
rcu_nocb_lock_irqsave(rdp, flags);
|
||
rcu_accelerate_cbs_unlocked(rnp, rdp);
|
||
rcu_nocb_unlock_irqrestore(rdp, flags);
|
||
}
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Check to see if there is a new grace period of which this CPU
|
||
* is not yet aware, and if so, set up local rcu_data state for it.
|
||
* Otherwise, see if this CPU has just passed through its first
|
||
* quiescent state for this grace period, and record that fact if so.
|
||
*/
|
||
static void
|
||
rcu_check_quiescent_state(struct rcu_data *rdp)
|
||
{
|
||
/* Check for grace-period ends and beginnings. */
|
||
note_gp_changes(rdp);
|
||
|
||
/*
|
||
* Does this CPU still need to do its part for current grace period?
|
||
* If no, return and let the other CPUs do their part as well.
|
||
*/
|
||
if (!rdp->core_needs_qs)
|
||
return;
|
||
|
||
/*
|
||
* Was there a quiescent state since the beginning of the grace
|
||
* period? If no, then exit and wait for the next call.
|
||
*/
|
||
if (rdp->cpu_no_qs.b.norm)
|
||
return;
|
||
|
||
/*
|
||
* Tell RCU we are done (but rcu_report_qs_rdp() will be the
|
||
* judge of that).
|
||
*/
|
||
rcu_report_qs_rdp(rdp);
|
||
}
|
||
|
||
/* Return true if callback-invocation time limit exceeded. */
|
||
static bool rcu_do_batch_check_time(long count, long tlimit,
|
||
bool jlimit_check, unsigned long jlimit)
|
||
{
|
||
// Invoke local_clock() only once per 32 consecutive callbacks.
|
||
return unlikely(tlimit) &&
|
||
(!likely(count & 31) ||
|
||
(IS_ENABLED(CONFIG_RCU_DOUBLE_CHECK_CB_TIME) &&
|
||
jlimit_check && time_after(jiffies, jlimit))) &&
|
||
local_clock() >= tlimit;
|
||
}
|
||
|
||
/*
|
||
* Invoke any RCU callbacks that have made it to the end of their grace
|
||
* period. Throttle as specified by rdp->blimit.
|
||
*/
|
||
static void rcu_do_batch(struct rcu_data *rdp)
|
||
{
|
||
long bl;
|
||
long count = 0;
|
||
int div;
|
||
bool __maybe_unused empty;
|
||
unsigned long flags;
|
||
unsigned long jlimit;
|
||
bool jlimit_check = false;
|
||
long pending;
|
||
struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
|
||
struct rcu_head *rhp;
|
||
long tlimit = 0;
|
||
|
||
/* If no callbacks are ready, just return. */
|
||
if (!rcu_segcblist_ready_cbs(&rdp->cblist)) {
|
||
trace_rcu_batch_start(rcu_state.name,
|
||
rcu_segcblist_n_cbs(&rdp->cblist), 0);
|
||
trace_rcu_batch_end(rcu_state.name, 0,
|
||
!rcu_segcblist_empty(&rdp->cblist),
|
||
need_resched(), is_idle_task(current),
|
||
rcu_is_callbacks_kthread(rdp));
|
||
return;
|
||
}
|
||
|
||
/*
|
||
* Extract the list of ready callbacks, disabling IRQs to prevent
|
||
* races with call_rcu() from interrupt handlers. Leave the
|
||
* callback counts, as rcu_barrier() needs to be conservative.
|
||
*/
|
||
rcu_nocb_lock_irqsave(rdp, flags);
|
||
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
|
||
pending = rcu_segcblist_get_seglen(&rdp->cblist, RCU_DONE_TAIL);
|
||
div = READ_ONCE(rcu_divisor);
|
||
div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
|
||
bl = max(rdp->blimit, pending >> div);
|
||
if ((in_serving_softirq() || rdp->rcu_cpu_kthread_status == RCU_KTHREAD_RUNNING) &&
|
||
(IS_ENABLED(CONFIG_RCU_DOUBLE_CHECK_CB_TIME) || unlikely(bl > 100))) {
|
||
const long npj = NSEC_PER_SEC / HZ;
|
||
long rrn = READ_ONCE(rcu_resched_ns);
|
||
|
||
rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn;
|
||
tlimit = local_clock() + rrn;
|
||
jlimit = jiffies + (rrn + npj + 1) / npj;
|
||
jlimit_check = true;
|
||
}
|
||
trace_rcu_batch_start(rcu_state.name,
|
||
rcu_segcblist_n_cbs(&rdp->cblist), bl);
|
||
rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl);
|
||
if (rcu_rdp_is_offloaded(rdp))
|
||
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
|
||
|
||
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbDequeued"));
|
||
rcu_nocb_unlock_irqrestore(rdp, flags);
|
||
|
||
/* Invoke callbacks. */
|
||
tick_dep_set_task(current, TICK_DEP_BIT_RCU);
|
||
rhp = rcu_cblist_dequeue(&rcl);
|
||
|
||
for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) {
|
||
rcu_callback_t f;
|
||
|
||
count++;
|
||
debug_rcu_head_unqueue(rhp);
|
||
|
||
rcu_lock_acquire(&rcu_callback_map);
|
||
trace_rcu_invoke_callback(rcu_state.name, rhp);
|
||
|
||
f = rhp->func;
|
||
debug_rcu_head_callback(rhp);
|
||
WRITE_ONCE(rhp->func, (rcu_callback_t)0L);
|
||
f(rhp);
|
||
|
||
rcu_lock_release(&rcu_callback_map);
|
||
|
||
/*
|
||
* Stop only if limit reached and CPU has something to do.
|
||
*/
|
||
if (in_serving_softirq()) {
|
||
if (count >= bl && (need_resched() || !is_idle_task(current)))
|
||
break;
|
||
/*
|
||
* Make sure we don't spend too much time here and deprive other
|
||
* softirq vectors of CPU cycles.
|
||
*/
|
||
if (rcu_do_batch_check_time(count, tlimit, jlimit_check, jlimit))
|
||
break;
|
||
} else {
|
||
// In rcuc/rcuoc context, so no worries about
|
||
// depriving other softirq vectors of CPU cycles.
|
||
local_bh_enable();
|
||
lockdep_assert_irqs_enabled();
|
||
cond_resched_tasks_rcu_qs();
|
||
lockdep_assert_irqs_enabled();
|
||
local_bh_disable();
|
||
// But rcuc kthreads can delay quiescent-state
|
||
// reporting, so check time limits for them.
|
||
if (rdp->rcu_cpu_kthread_status == RCU_KTHREAD_RUNNING &&
|
||
rcu_do_batch_check_time(count, tlimit, jlimit_check, jlimit)) {
|
||
rdp->rcu_cpu_has_work = 1;
|
||
break;
|
||
}
|
||
}
|
||
}
|
||
|
||
rcu_nocb_lock_irqsave(rdp, flags);
|
||
rdp->n_cbs_invoked += count;
|
||
trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(),
|
||
is_idle_task(current), rcu_is_callbacks_kthread(rdp));
|
||
|
||
/* Update counts and requeue any remaining callbacks. */
|
||
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
|
||
rcu_segcblist_add_len(&rdp->cblist, -count);
|
||
|
||
/* Reinstate batch limit if we have worked down the excess. */
|
||
count = rcu_segcblist_n_cbs(&rdp->cblist);
|
||
if (rdp->blimit >= DEFAULT_MAX_RCU_BLIMIT && count <= qlowmark)
|
||
rdp->blimit = blimit;
|
||
|
||
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
|
||
if (count == 0 && rdp->qlen_last_fqs_check != 0) {
|
||
rdp->qlen_last_fqs_check = 0;
|
||
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
|
||
} else if (count < rdp->qlen_last_fqs_check - qhimark)
|
||
rdp->qlen_last_fqs_check = count;
|
||
|
||
/*
|
||
* The following usually indicates a double call_rcu(). To track
|
||
* this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.
|
||
*/
|
||
empty = rcu_segcblist_empty(&rdp->cblist);
|
||
WARN_ON_ONCE(count == 0 && !empty);
|
||
WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
||
count != 0 && empty);
|
||
WARN_ON_ONCE(count == 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) != 0);
|
||
WARN_ON_ONCE(!empty && rcu_segcblist_n_segment_cbs(&rdp->cblist) == 0);
|
||
|
||
rcu_nocb_unlock_irqrestore(rdp, flags);
|
||
|
||
tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
|
||
}
|
||
|
||
/*
|
||
* This function is invoked from each scheduling-clock interrupt,
|
||
* and checks to see if this CPU is in a non-context-switch quiescent
|
||
* state, for example, user mode or idle loop. It also schedules RCU
|
||
* core processing. If the current grace period has gone on too long,
|
||
* it will ask the scheduler to manufacture a context switch for the sole
|
||
* purpose of providing the needed quiescent state.
|
||
*/
|
||
void rcu_sched_clock_irq(int user)
|
||
{
|
||
unsigned long j;
|
||
|
||
if (IS_ENABLED(CONFIG_PROVE_RCU)) {
|
||
j = jiffies;
|
||
WARN_ON_ONCE(time_before(j, __this_cpu_read(rcu_data.last_sched_clock)));
|
||
__this_cpu_write(rcu_data.last_sched_clock, j);
|
||
}
|
||
trace_rcu_utilization(TPS("Start scheduler-tick"));
|
||
lockdep_assert_irqs_disabled();
|
||
raw_cpu_inc(rcu_data.ticks_this_gp);
|
||
/* The load-acquire pairs with the store-release setting to true. */
|
||
if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
|
||
/* Idle and userspace execution already are quiescent states. */
|
||
if (!rcu_is_cpu_rrupt_from_idle() && !user) {
|
||
set_tsk_need_resched(current);
|
||
set_preempt_need_resched();
|
||
}
|
||
__this_cpu_write(rcu_data.rcu_urgent_qs, false);
|
||
}
|
||
rcu_flavor_sched_clock_irq(user);
|
||
if (rcu_pending(user))
|
||
invoke_rcu_core();
|
||
if (user || rcu_is_cpu_rrupt_from_idle())
|
||
rcu_note_voluntary_context_switch(current);
|
||
lockdep_assert_irqs_disabled();
|
||
|
||
trace_rcu_utilization(TPS("End scheduler-tick"));
|
||
}
|
||
|
||
/*
|
||
* Scan the leaf rcu_node structures. For each structure on which all
|
||
* CPUs have reported a quiescent state and on which there are tasks
|
||
* blocking the current grace period, initiate RCU priority boosting.
|
||
* Otherwise, invoke the specified function to check dyntick state for
|
||
* each CPU that has not yet reported a quiescent state.
|
||
*/
|
||
static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
|
||
{
|
||
int cpu;
|
||
unsigned long flags;
|
||
struct rcu_node *rnp;
|
||
|
||
rcu_state.cbovld = rcu_state.cbovldnext;
|
||
rcu_state.cbovldnext = false;
|
||
rcu_for_each_leaf_node(rnp) {
|
||
unsigned long mask = 0;
|
||
unsigned long rsmask = 0;
|
||
|
||
cond_resched_tasks_rcu_qs();
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
rcu_state.cbovldnext |= !!rnp->cbovldmask;
|
||
if (rnp->qsmask == 0) {
|
||
if (rcu_preempt_blocked_readers_cgp(rnp)) {
|
||
/*
|
||
* No point in scanning bits because they
|
||
* are all zero. But we might need to
|
||
* priority-boost blocked readers.
|
||
*/
|
||
rcu_initiate_boost(rnp, flags);
|
||
/* rcu_initiate_boost() releases rnp->lock */
|
||
continue;
|
||
}
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
continue;
|
||
}
|
||
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->qsmask) {
|
||
struct rcu_data *rdp;
|
||
int ret;
|
||
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
ret = f(rdp);
|
||
if (ret > 0) {
|
||
mask |= rdp->grpmask;
|
||
rcu_disable_urgency_upon_qs(rdp);
|
||
}
|
||
if (ret < 0)
|
||
rsmask |= rdp->grpmask;
|
||
}
|
||
if (mask != 0) {
|
||
/* Idle/offline CPUs, report (releases rnp->lock). */
|
||
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
||
} else {
|
||
/* Nothing to do here, so just drop the lock. */
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
}
|
||
|
||
for_each_leaf_node_cpu_mask(rnp, cpu, rsmask)
|
||
resched_cpu(cpu);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Force quiescent states on reluctant CPUs, and also detect which
|
||
* CPUs are in dyntick-idle mode.
|
||
*/
|
||
void rcu_force_quiescent_state(void)
|
||
{
|
||
unsigned long flags;
|
||
bool ret;
|
||
struct rcu_node *rnp;
|
||
struct rcu_node *rnp_old = NULL;
|
||
|
||
if (!rcu_gp_in_progress())
|
||
return;
|
||
/* Funnel through hierarchy to reduce memory contention. */
|
||
rnp = raw_cpu_read(rcu_data.mynode);
|
||
for (; rnp != NULL; rnp = rnp->parent) {
|
||
ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
|
||
!raw_spin_trylock(&rnp->fqslock);
|
||
if (rnp_old != NULL)
|
||
raw_spin_unlock(&rnp_old->fqslock);
|
||
if (ret)
|
||
return;
|
||
rnp_old = rnp;
|
||
}
|
||
/* rnp_old == rcu_get_root(), rnp == NULL. */
|
||
|
||
/* Reached the root of the rcu_node tree, acquire lock. */
|
||
raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
|
||
raw_spin_unlock(&rnp_old->fqslock);
|
||
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) {
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
|
||
return; /* Someone beat us to it. */
|
||
}
|
||
WRITE_ONCE(rcu_state.gp_flags,
|
||
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS);
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
|
||
rcu_gp_kthread_wake();
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
|
||
|
||
// Workqueue handler for an RCU reader for kernels enforcing struct RCU
|
||
// grace periods.
|
||
static void strict_work_handler(struct work_struct *work)
|
||
{
|
||
rcu_read_lock();
|
||
rcu_read_unlock();
|
||
}
|
||
|
||
/* Perform RCU core processing work for the current CPU. */
|
||
static __latent_entropy void rcu_core(void)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
|
||
struct rcu_node *rnp = rdp->mynode;
|
||
/*
|
||
* On RT rcu_core() can be preempted when IRQs aren't disabled.
|
||
* Therefore this function can race with concurrent NOCB (de-)offloading
|
||
* on this CPU and the below condition must be considered volatile.
|
||
* However if we race with:
|
||
*
|
||
* _ Offloading: In the worst case we accelerate or process callbacks
|
||
* concurrently with NOCB kthreads. We are guaranteed to
|
||
* call rcu_nocb_lock() if that happens.
|
||
*
|
||
* _ Deoffloading: In the worst case we miss callbacks acceleration or
|
||
* processing. This is fine because the early stage
|
||
* of deoffloading invokes rcu_core() after setting
|
||
* SEGCBLIST_RCU_CORE. So we guarantee that we'll process
|
||
* what could have been dismissed without the need to wait
|
||
* for the next rcu_pending() check in the next jiffy.
|
||
*/
|
||
const bool do_batch = !rcu_segcblist_completely_offloaded(&rdp->cblist);
|
||
|
||
if (cpu_is_offline(smp_processor_id()))
|
||
return;
|
||
trace_rcu_utilization(TPS("Start RCU core"));
|
||
WARN_ON_ONCE(!rdp->beenonline);
|
||
|
||
/* Report any deferred quiescent states if preemption enabled. */
|
||
if (IS_ENABLED(CONFIG_PREEMPT_COUNT) && (!(preempt_count() & PREEMPT_MASK))) {
|
||
rcu_preempt_deferred_qs(current);
|
||
} else if (rcu_preempt_need_deferred_qs(current)) {
|
||
set_tsk_need_resched(current);
|
||
set_preempt_need_resched();
|
||
}
|
||
|
||
/* Update RCU state based on any recent quiescent states. */
|
||
rcu_check_quiescent_state(rdp);
|
||
|
||
/* No grace period and unregistered callbacks? */
|
||
if (!rcu_gp_in_progress() &&
|
||
rcu_segcblist_is_enabled(&rdp->cblist) && do_batch) {
|
||
rcu_nocb_lock_irqsave(rdp, flags);
|
||
if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
|
||
rcu_accelerate_cbs_unlocked(rnp, rdp);
|
||
rcu_nocb_unlock_irqrestore(rdp, flags);
|
||
}
|
||
|
||
rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());
|
||
|
||
/* If there are callbacks ready, invoke them. */
|
||
if (do_batch && rcu_segcblist_ready_cbs(&rdp->cblist) &&
|
||
likely(READ_ONCE(rcu_scheduler_fully_active))) {
|
||
rcu_do_batch(rdp);
|
||
/* Re-invoke RCU core processing if there are callbacks remaining. */
|
||
if (rcu_segcblist_ready_cbs(&rdp->cblist))
|
||
invoke_rcu_core();
|
||
}
|
||
|
||
/* Do any needed deferred wakeups of rcuo kthreads. */
|
||
do_nocb_deferred_wakeup(rdp);
|
||
trace_rcu_utilization(TPS("End RCU core"));
|
||
|
||
// If strict GPs, schedule an RCU reader in a clean environment.
|
||
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
|
||
queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work);
|
||
}
|
||
|
||
static void rcu_core_si(struct softirq_action *h)
|
||
{
|
||
rcu_core();
|
||
}
|
||
|
||
static void rcu_wake_cond(struct task_struct *t, int status)
|
||
{
|
||
/*
|
||
* If the thread is yielding, only wake it when this
|
||
* is invoked from idle
|
||
*/
|
||
if (t && (status != RCU_KTHREAD_YIELDING || is_idle_task(current)))
|
||
wake_up_process(t);
|
||
}
|
||
|
||
static void invoke_rcu_core_kthread(void)
|
||
{
|
||
struct task_struct *t;
|
||
unsigned long flags;
|
||
|
||
local_irq_save(flags);
|
||
__this_cpu_write(rcu_data.rcu_cpu_has_work, 1);
|
||
t = __this_cpu_read(rcu_data.rcu_cpu_kthread_task);
|
||
if (t != NULL && t != current)
|
||
rcu_wake_cond(t, __this_cpu_read(rcu_data.rcu_cpu_kthread_status));
|
||
local_irq_restore(flags);
|
||
}
|
||
|
||
/*
|
||
* Wake up this CPU's rcuc kthread to do RCU core processing.
|
||
*/
|
||
static void invoke_rcu_core(void)
|
||
{
|
||
if (!cpu_online(smp_processor_id()))
|
||
return;
|
||
if (use_softirq)
|
||
raise_softirq(RCU_SOFTIRQ);
|
||
else
|
||
invoke_rcu_core_kthread();
|
||
}
|
||
|
||
static void rcu_cpu_kthread_park(unsigned int cpu)
|
||
{
|
||
per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
|
||
}
|
||
|
||
static int rcu_cpu_kthread_should_run(unsigned int cpu)
|
||
{
|
||
return __this_cpu_read(rcu_data.rcu_cpu_has_work);
|
||
}
|
||
|
||
/*
|
||
* Per-CPU kernel thread that invokes RCU callbacks. This replaces
|
||
* the RCU softirq used in configurations of RCU that do not support RCU
|
||
* priority boosting.
|
||
*/
|
||
static void rcu_cpu_kthread(unsigned int cpu)
|
||
{
|
||
unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status);
|
||
char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
|
||
unsigned long *j = this_cpu_ptr(&rcu_data.rcuc_activity);
|
||
int spincnt;
|
||
|
||
trace_rcu_utilization(TPS("Start CPU kthread@rcu_run"));
|
||
for (spincnt = 0; spincnt < 10; spincnt++) {
|
||
WRITE_ONCE(*j, jiffies);
|
||
local_bh_disable();
|
||
*statusp = RCU_KTHREAD_RUNNING;
|
||
local_irq_disable();
|
||
work = *workp;
|
||
WRITE_ONCE(*workp, 0);
|
||
local_irq_enable();
|
||
if (work)
|
||
rcu_core();
|
||
local_bh_enable();
|
||
if (!READ_ONCE(*workp)) {
|
||
trace_rcu_utilization(TPS("End CPU kthread@rcu_wait"));
|
||
*statusp = RCU_KTHREAD_WAITING;
|
||
return;
|
||
}
|
||
}
|
||
*statusp = RCU_KTHREAD_YIELDING;
|
||
trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield"));
|
||
schedule_timeout_idle(2);
|
||
trace_rcu_utilization(TPS("End CPU kthread@rcu_yield"));
|
||
*statusp = RCU_KTHREAD_WAITING;
|
||
WRITE_ONCE(*j, jiffies);
|
||
}
|
||
|
||
static struct smp_hotplug_thread rcu_cpu_thread_spec = {
|
||
.store = &rcu_data.rcu_cpu_kthread_task,
|
||
.thread_should_run = rcu_cpu_kthread_should_run,
|
||
.thread_fn = rcu_cpu_kthread,
|
||
.thread_comm = "rcuc/%u",
|
||
.setup = rcu_cpu_kthread_setup,
|
||
.park = rcu_cpu_kthread_park,
|
||
};
|
||
|
||
/*
|
||
* Spawn per-CPU RCU core processing kthreads.
|
||
*/
|
||
static int __init rcu_spawn_core_kthreads(void)
|
||
{
|
||
int cpu;
|
||
|
||
for_each_possible_cpu(cpu)
|
||
per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
|
||
if (use_softirq)
|
||
return 0;
|
||
WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec),
|
||
"%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__);
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Handle any core-RCU processing required by a call_rcu() invocation.
|
||
*/
|
||
static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head,
|
||
unsigned long flags)
|
||
{
|
||
/*
|
||
* If called from an extended quiescent state, invoke the RCU
|
||
* core in order to force a re-evaluation of RCU's idleness.
|
||
*/
|
||
if (!rcu_is_watching())
|
||
invoke_rcu_core();
|
||
|
||
/* If interrupts were disabled or CPU offline, don't invoke RCU core. */
|
||
if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
|
||
return;
|
||
|
||
/*
|
||
* Force the grace period if too many callbacks or too long waiting.
|
||
* Enforce hysteresis, and don't invoke rcu_force_quiescent_state()
|
||
* if some other CPU has recently done so. Also, don't bother
|
||
* invoking rcu_force_quiescent_state() if the newly enqueued callback
|
||
* is the only one waiting for a grace period to complete.
|
||
*/
|
||
if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) >
|
||
rdp->qlen_last_fqs_check + qhimark)) {
|
||
|
||
/* Are we ignoring a completed grace period? */
|
||
note_gp_changes(rdp);
|
||
|
||
/* Start a new grace period if one not already started. */
|
||
if (!rcu_gp_in_progress()) {
|
||
rcu_accelerate_cbs_unlocked(rdp->mynode, rdp);
|
||
} else {
|
||
/* Give the grace period a kick. */
|
||
rdp->blimit = DEFAULT_MAX_RCU_BLIMIT;
|
||
if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap &&
|
||
rcu_segcblist_first_pend_cb(&rdp->cblist) != head)
|
||
rcu_force_quiescent_state();
|
||
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
|
||
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
|
||
}
|
||
}
|
||
}
|
||
|
||
/*
|
||
* RCU callback function to leak a callback.
|
||
*/
|
||
static void rcu_leak_callback(struct rcu_head *rhp)
|
||
{
|
||
}
|
||
|
||
/*
|
||
* Check and if necessary update the leaf rcu_node structure's
|
||
* ->cbovldmask bit corresponding to the current CPU based on that CPU's
|
||
* number of queued RCU callbacks. The caller must hold the leaf rcu_node
|
||
* structure's ->lock.
|
||
*/
|
||
static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp)
|
||
{
|
||
raw_lockdep_assert_held_rcu_node(rnp);
|
||
if (qovld_calc <= 0)
|
||
return; // Early boot and wildcard value set.
|
||
if (rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc)
|
||
WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask | rdp->grpmask);
|
||
else
|
||
WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask & ~rdp->grpmask);
|
||
}
|
||
|
||
/*
|
||
* Check and if necessary update the leaf rcu_node structure's
|
||
* ->cbovldmask bit corresponding to the current CPU based on that CPU's
|
||
* number of queued RCU callbacks. No locks need be held, but the
|
||
* caller must have disabled interrupts.
|
||
*
|
||
* Note that this function ignores the possibility that there are a lot
|
||
* of callbacks all of which have already seen the end of their respective
|
||
* grace periods. This omission is due to the need for no-CBs CPUs to
|
||
* be holding ->nocb_lock to do this check, which is too heavy for a
|
||
* common-case operation.
|
||
*/
|
||
static void check_cb_ovld(struct rcu_data *rdp)
|
||
{
|
||
struct rcu_node *const rnp = rdp->mynode;
|
||
|
||
if (qovld_calc <= 0 ||
|
||
((rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) ==
|
||
!!(READ_ONCE(rnp->cbovldmask) & rdp->grpmask)))
|
||
return; // Early boot wildcard value or already set correctly.
|
||
raw_spin_lock_rcu_node(rnp);
|
||
check_cb_ovld_locked(rdp, rnp);
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
}
|
||
|
||
static void
|
||
__call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in)
|
||
{
|
||
static atomic_t doublefrees;
|
||
unsigned long flags;
|
||
bool lazy;
|
||
struct rcu_data *rdp;
|
||
bool was_alldone;
|
||
|
||
/* Misaligned rcu_head! */
|
||
WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1));
|
||
|
||
if (debug_rcu_head_queue(head)) {
|
||
/*
|
||
* Probable double call_rcu(), so leak the callback.
|
||
* Use rcu:rcu_callback trace event to find the previous
|
||
* time callback was passed to call_rcu().
|
||
*/
|
||
if (atomic_inc_return(&doublefrees) < 4) {
|
||
pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func);
|
||
mem_dump_obj(head);
|
||
}
|
||
WRITE_ONCE(head->func, rcu_leak_callback);
|
||
return;
|
||
}
|
||
head->func = func;
|
||
head->next = NULL;
|
||
kasan_record_aux_stack_noalloc(head);
|
||
local_irq_save(flags);
|
||
rdp = this_cpu_ptr(&rcu_data);
|
||
lazy = lazy_in && !rcu_async_should_hurry();
|
||
|
||
/* Add the callback to our list. */
|
||
if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist))) {
|
||
// This can trigger due to call_rcu() from offline CPU:
|
||
WARN_ON_ONCE(rcu_scheduler_active != RCU_SCHEDULER_INACTIVE);
|
||
WARN_ON_ONCE(!rcu_is_watching());
|
||
// Very early boot, before rcu_init(). Initialize if needed
|
||
// and then drop through to queue the callback.
|
||
if (rcu_segcblist_empty(&rdp->cblist))
|
||
rcu_segcblist_init(&rdp->cblist);
|
||
}
|
||
|
||
check_cb_ovld(rdp);
|
||
if (rcu_nocb_try_bypass(rdp, head, &was_alldone, flags, lazy))
|
||
return; // Enqueued onto ->nocb_bypass, so just leave.
|
||
// If no-CBs CPU gets here, rcu_nocb_try_bypass() acquired ->nocb_lock.
|
||
rcu_segcblist_enqueue(&rdp->cblist, head);
|
||
if (__is_kvfree_rcu_offset((unsigned long)func))
|
||
trace_rcu_kvfree_callback(rcu_state.name, head,
|
||
(unsigned long)func,
|
||
rcu_segcblist_n_cbs(&rdp->cblist));
|
||
else
|
||
trace_rcu_callback(rcu_state.name, head,
|
||
rcu_segcblist_n_cbs(&rdp->cblist));
|
||
|
||
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCBQueued"));
|
||
|
||
/* Go handle any RCU core processing required. */
|
||
if (unlikely(rcu_rdp_is_offloaded(rdp))) {
|
||
__call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */
|
||
} else {
|
||
__call_rcu_core(rdp, head, flags);
|
||
local_irq_restore(flags);
|
||
}
|
||
}
|
||
|
||
#ifdef CONFIG_RCU_LAZY
|
||
/**
|
||
* call_rcu_hurry() - Queue RCU callback for invocation after grace period, and
|
||
* flush all lazy callbacks (including the new one) to the main ->cblist while
|
||
* doing so.
|
||
*
|
||
* @head: structure to be used for queueing the RCU updates.
|
||
* @func: actual callback function to be invoked after the grace period
|
||
*
|
||
* The callback function will be invoked some time after a full grace
|
||
* period elapses, in other words after all pre-existing RCU read-side
|
||
* critical sections have completed.
|
||
*
|
||
* Use this API instead of call_rcu() if you don't want the callback to be
|
||
* invoked after very long periods of time, which can happen on systems without
|
||
* memory pressure and on systems which are lightly loaded or mostly idle.
|
||
* This function will cause callbacks to be invoked sooner than later at the
|
||
* expense of extra power. Other than that, this function is identical to, and
|
||
* reuses call_rcu()'s logic. Refer to call_rcu() for more details about memory
|
||
* ordering and other functionality.
|
||
*/
|
||
void call_rcu_hurry(struct rcu_head *head, rcu_callback_t func)
|
||
{
|
||
__call_rcu_common(head, func, false);
|
||
}
|
||
EXPORT_SYMBOL_GPL(call_rcu_hurry);
|
||
#endif
|
||
|
||
/**
|
||
* call_rcu() - Queue an RCU callback for invocation after a grace period.
|
||
* By default the callbacks are 'lazy' and are kept hidden from the main
|
||
* ->cblist to prevent starting of grace periods too soon.
|
||
* If you desire grace periods to start very soon, use call_rcu_hurry().
|
||
*
|
||
* @head: structure to be used for queueing the RCU updates.
|
||
* @func: actual callback function to be invoked after the grace period
|
||
*
|
||
* The callback function will be invoked some time after a full grace
|
||
* period elapses, in other words after all pre-existing RCU read-side
|
||
* critical sections have completed. However, the callback function
|
||
* might well execute concurrently with RCU read-side critical sections
|
||
* that started after call_rcu() was invoked.
|
||
*
|
||
* RCU read-side critical sections are delimited by rcu_read_lock()
|
||
* and rcu_read_unlock(), and may be nested. In addition, but only in
|
||
* v5.0 and later, regions of code across which interrupts, preemption,
|
||
* or softirqs have been disabled also serve as RCU read-side critical
|
||
* sections. This includes hardware interrupt handlers, softirq handlers,
|
||
* and NMI handlers.
|
||
*
|
||
* Note that all CPUs must agree that the grace period extended beyond
|
||
* all pre-existing RCU read-side critical section. On systems with more
|
||
* than one CPU, this means that when "func()" is invoked, each CPU is
|
||
* guaranteed to have executed a full memory barrier since the end of its
|
||
* last RCU read-side critical section whose beginning preceded the call
|
||
* to call_rcu(). It also means that each CPU executing an RCU read-side
|
||
* critical section that continues beyond the start of "func()" must have
|
||
* executed a memory barrier after the call_rcu() but before the beginning
|
||
* of that RCU read-side critical section. Note that these guarantees
|
||
* include CPUs that are offline, idle, or executing in user mode, as
|
||
* well as CPUs that are executing in the kernel.
|
||
*
|
||
* Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
|
||
* resulting RCU callback function "func()", then both CPU A and CPU B are
|
||
* guaranteed to execute a full memory barrier during the time interval
|
||
* between the call to call_rcu() and the invocation of "func()" -- even
|
||
* if CPU A and CPU B are the same CPU (but again only if the system has
|
||
* more than one CPU).
|
||
*
|
||
* Implementation of these memory-ordering guarantees is described here:
|
||
* Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst.
|
||
*/
|
||
void call_rcu(struct rcu_head *head, rcu_callback_t func)
|
||
{
|
||
__call_rcu_common(head, func, IS_ENABLED(CONFIG_RCU_LAZY));
|
||
}
|
||
EXPORT_SYMBOL_GPL(call_rcu);
|
||
|
||
/* Maximum number of jiffies to wait before draining a batch. */
|
||
#define KFREE_DRAIN_JIFFIES (5 * HZ)
|
||
#define KFREE_N_BATCHES 2
|
||
#define FREE_N_CHANNELS 2
|
||
|
||
/**
|
||
* struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
|
||
* @list: List node. All blocks are linked between each other
|
||
* @gp_snap: Snapshot of RCU state for objects placed to this bulk
|
||
* @nr_records: Number of active pointers in the array
|
||
* @records: Array of the kvfree_rcu() pointers
|
||
*/
|
||
struct kvfree_rcu_bulk_data {
|
||
struct list_head list;
|
||
struct rcu_gp_oldstate gp_snap;
|
||
unsigned long nr_records;
|
||
void *records[];
|
||
};
|
||
|
||
/*
|
||
* This macro defines how many entries the "records" array
|
||
* will contain. It is based on the fact that the size of
|
||
* kvfree_rcu_bulk_data structure becomes exactly one page.
|
||
*/
|
||
#define KVFREE_BULK_MAX_ENTR \
|
||
((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *))
|
||
|
||
/**
|
||
* struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
|
||
* @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
|
||
* @head_free: List of kfree_rcu() objects waiting for a grace period
|
||
* @head_free_gp_snap: Grace-period snapshot to check for attempted premature frees.
|
||
* @bulk_head_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
|
||
* @krcp: Pointer to @kfree_rcu_cpu structure
|
||
*/
|
||
|
||
struct kfree_rcu_cpu_work {
|
||
struct rcu_work rcu_work;
|
||
struct rcu_head *head_free;
|
||
struct rcu_gp_oldstate head_free_gp_snap;
|
||
struct list_head bulk_head_free[FREE_N_CHANNELS];
|
||
struct kfree_rcu_cpu *krcp;
|
||
};
|
||
|
||
/**
|
||
* struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period
|
||
* @head: List of kfree_rcu() objects not yet waiting for a grace period
|
||
* @head_gp_snap: Snapshot of RCU state for objects placed to "@head"
|
||
* @bulk_head: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
|
||
* @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
|
||
* @lock: Synchronize access to this structure
|
||
* @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
|
||
* @initialized: The @rcu_work fields have been initialized
|
||
* @head_count: Number of objects in rcu_head singular list
|
||
* @bulk_count: Number of objects in bulk-list
|
||
* @bkvcache:
|
||
* A simple cache list that contains objects for reuse purpose.
|
||
* In order to save some per-cpu space the list is singular.
|
||
* Even though it is lockless an access has to be protected by the
|
||
* per-cpu lock.
|
||
* @page_cache_work: A work to refill the cache when it is empty
|
||
* @backoff_page_cache_fill: Delay cache refills
|
||
* @work_in_progress: Indicates that page_cache_work is running
|
||
* @hrtimer: A hrtimer for scheduling a page_cache_work
|
||
* @nr_bkv_objs: number of allocated objects at @bkvcache.
|
||
*
|
||
* This is a per-CPU structure. The reason that it is not included in
|
||
* the rcu_data structure is to permit this code to be extracted from
|
||
* the RCU files. Such extraction could allow further optimization of
|
||
* the interactions with the slab allocators.
|
||
*/
|
||
struct kfree_rcu_cpu {
|
||
// Objects queued on a linked list
|
||
// through their rcu_head structures.
|
||
struct rcu_head *head;
|
||
unsigned long head_gp_snap;
|
||
atomic_t head_count;
|
||
|
||
// Objects queued on a bulk-list.
|
||
struct list_head bulk_head[FREE_N_CHANNELS];
|
||
atomic_t bulk_count[FREE_N_CHANNELS];
|
||
|
||
struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
|
||
raw_spinlock_t lock;
|
||
struct delayed_work monitor_work;
|
||
bool initialized;
|
||
|
||
struct delayed_work page_cache_work;
|
||
atomic_t backoff_page_cache_fill;
|
||
atomic_t work_in_progress;
|
||
struct hrtimer hrtimer;
|
||
|
||
struct llist_head bkvcache;
|
||
int nr_bkv_objs;
|
||
};
|
||
|
||
static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
|
||
.lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock),
|
||
};
|
||
|
||
static __always_inline void
|
||
debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead)
|
||
{
|
||
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
|
||
int i;
|
||
|
||
for (i = 0; i < bhead->nr_records; i++)
|
||
debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
|
||
#endif
|
||
}
|
||
|
||
static inline struct kfree_rcu_cpu *
|
||
krc_this_cpu_lock(unsigned long *flags)
|
||
{
|
||
struct kfree_rcu_cpu *krcp;
|
||
|
||
local_irq_save(*flags); // For safely calling this_cpu_ptr().
|
||
krcp = this_cpu_ptr(&krc);
|
||
raw_spin_lock(&krcp->lock);
|
||
|
||
return krcp;
|
||
}
|
||
|
||
static inline void
|
||
krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
|
||
{
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
}
|
||
|
||
static inline struct kvfree_rcu_bulk_data *
|
||
get_cached_bnode(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
if (!krcp->nr_bkv_objs)
|
||
return NULL;
|
||
|
||
WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs - 1);
|
||
return (struct kvfree_rcu_bulk_data *)
|
||
llist_del_first(&krcp->bkvcache);
|
||
}
|
||
|
||
static inline bool
|
||
put_cached_bnode(struct kfree_rcu_cpu *krcp,
|
||
struct kvfree_rcu_bulk_data *bnode)
|
||
{
|
||
// Check the limit.
|
||
if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
|
||
return false;
|
||
|
||
llist_add((struct llist_node *) bnode, &krcp->bkvcache);
|
||
WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs + 1);
|
||
return true;
|
||
}
|
||
|
||
static int
|
||
drain_page_cache(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
unsigned long flags;
|
||
struct llist_node *page_list, *pos, *n;
|
||
int freed = 0;
|
||
|
||
if (!rcu_min_cached_objs)
|
||
return 0;
|
||
|
||
raw_spin_lock_irqsave(&krcp->lock, flags);
|
||
page_list = llist_del_all(&krcp->bkvcache);
|
||
WRITE_ONCE(krcp->nr_bkv_objs, 0);
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
|
||
llist_for_each_safe(pos, n, page_list) {
|
||
free_page((unsigned long)pos);
|
||
freed++;
|
||
}
|
||
|
||
return freed;
|
||
}
|
||
|
||
static void
|
||
kvfree_rcu_bulk(struct kfree_rcu_cpu *krcp,
|
||
struct kvfree_rcu_bulk_data *bnode, int idx)
|
||
{
|
||
unsigned long flags;
|
||
int i;
|
||
|
||
if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) {
|
||
debug_rcu_bhead_unqueue(bnode);
|
||
rcu_lock_acquire(&rcu_callback_map);
|
||
if (idx == 0) { // kmalloc() / kfree().
|
||
trace_rcu_invoke_kfree_bulk_callback(
|
||
rcu_state.name, bnode->nr_records,
|
||
bnode->records);
|
||
|
||
kfree_bulk(bnode->nr_records, bnode->records);
|
||
} else { // vmalloc() / vfree().
|
||
for (i = 0; i < bnode->nr_records; i++) {
|
||
trace_rcu_invoke_kvfree_callback(
|
||
rcu_state.name, bnode->records[i], 0);
|
||
|
||
vfree(bnode->records[i]);
|
||
}
|
||
}
|
||
rcu_lock_release(&rcu_callback_map);
|
||
}
|
||
|
||
raw_spin_lock_irqsave(&krcp->lock, flags);
|
||
if (put_cached_bnode(krcp, bnode))
|
||
bnode = NULL;
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
|
||
if (bnode)
|
||
free_page((unsigned long) bnode);
|
||
|
||
cond_resched_tasks_rcu_qs();
|
||
}
|
||
|
||
static void
|
||
kvfree_rcu_list(struct rcu_head *head)
|
||
{
|
||
struct rcu_head *next;
|
||
|
||
for (; head; head = next) {
|
||
void *ptr = (void *) head->func;
|
||
unsigned long offset = (void *) head - ptr;
|
||
|
||
next = head->next;
|
||
debug_rcu_head_unqueue((struct rcu_head *)ptr);
|
||
rcu_lock_acquire(&rcu_callback_map);
|
||
trace_rcu_invoke_kvfree_callback(rcu_state.name, head, offset);
|
||
|
||
if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset)))
|
||
kvfree(ptr);
|
||
|
||
rcu_lock_release(&rcu_callback_map);
|
||
cond_resched_tasks_rcu_qs();
|
||
}
|
||
}
|
||
|
||
/*
|
||
* This function is invoked in workqueue context after a grace period.
|
||
* It frees all the objects queued on ->bulk_head_free or ->head_free.
|
||
*/
|
||
static void kfree_rcu_work(struct work_struct *work)
|
||
{
|
||
unsigned long flags;
|
||
struct kvfree_rcu_bulk_data *bnode, *n;
|
||
struct list_head bulk_head[FREE_N_CHANNELS];
|
||
struct rcu_head *head;
|
||
struct kfree_rcu_cpu *krcp;
|
||
struct kfree_rcu_cpu_work *krwp;
|
||
struct rcu_gp_oldstate head_gp_snap;
|
||
int i;
|
||
|
||
krwp = container_of(to_rcu_work(work),
|
||
struct kfree_rcu_cpu_work, rcu_work);
|
||
krcp = krwp->krcp;
|
||
|
||
raw_spin_lock_irqsave(&krcp->lock, flags);
|
||
// Channels 1 and 2.
|
||
for (i = 0; i < FREE_N_CHANNELS; i++)
|
||
list_replace_init(&krwp->bulk_head_free[i], &bulk_head[i]);
|
||
|
||
// Channel 3.
|
||
head = krwp->head_free;
|
||
krwp->head_free = NULL;
|
||
head_gp_snap = krwp->head_free_gp_snap;
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
|
||
// Handle the first two channels.
|
||
for (i = 0; i < FREE_N_CHANNELS; i++) {
|
||
// Start from the tail page, so a GP is likely passed for it.
|
||
list_for_each_entry_safe(bnode, n, &bulk_head[i], list)
|
||
kvfree_rcu_bulk(krcp, bnode, i);
|
||
}
|
||
|
||
/*
|
||
* This is used when the "bulk" path can not be used for the
|
||
* double-argument of kvfree_rcu(). This happens when the
|
||
* page-cache is empty, which means that objects are instead
|
||
* queued on a linked list through their rcu_head structures.
|
||
* This list is named "Channel 3".
|
||
*/
|
||
if (head && !WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&head_gp_snap)))
|
||
kvfree_rcu_list(head);
|
||
}
|
||
|
||
static bool
|
||
need_offload_krc(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
int i;
|
||
|
||
for (i = 0; i < FREE_N_CHANNELS; i++)
|
||
if (!list_empty(&krcp->bulk_head[i]))
|
||
return true;
|
||
|
||
return !!READ_ONCE(krcp->head);
|
||
}
|
||
|
||
static bool
|
||
need_wait_for_krwp_work(struct kfree_rcu_cpu_work *krwp)
|
||
{
|
||
int i;
|
||
|
||
for (i = 0; i < FREE_N_CHANNELS; i++)
|
||
if (!list_empty(&krwp->bulk_head_free[i]))
|
||
return true;
|
||
|
||
return !!krwp->head_free;
|
||
}
|
||
|
||
static int krc_count(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
int sum = atomic_read(&krcp->head_count);
|
||
int i;
|
||
|
||
for (i = 0; i < FREE_N_CHANNELS; i++)
|
||
sum += atomic_read(&krcp->bulk_count[i]);
|
||
|
||
return sum;
|
||
}
|
||
|
||
static void
|
||
schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
long delay, delay_left;
|
||
|
||
delay = krc_count(krcp) >= KVFREE_BULK_MAX_ENTR ? 1:KFREE_DRAIN_JIFFIES;
|
||
if (delayed_work_pending(&krcp->monitor_work)) {
|
||
delay_left = krcp->monitor_work.timer.expires - jiffies;
|
||
if (delay < delay_left)
|
||
mod_delayed_work(system_wq, &krcp->monitor_work, delay);
|
||
return;
|
||
}
|
||
queue_delayed_work(system_wq, &krcp->monitor_work, delay);
|
||
}
|
||
|
||
static void
|
||
kvfree_rcu_drain_ready(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
struct list_head bulk_ready[FREE_N_CHANNELS];
|
||
struct kvfree_rcu_bulk_data *bnode, *n;
|
||
struct rcu_head *head_ready = NULL;
|
||
unsigned long flags;
|
||
int i;
|
||
|
||
raw_spin_lock_irqsave(&krcp->lock, flags);
|
||
for (i = 0; i < FREE_N_CHANNELS; i++) {
|
||
INIT_LIST_HEAD(&bulk_ready[i]);
|
||
|
||
list_for_each_entry_safe_reverse(bnode, n, &krcp->bulk_head[i], list) {
|
||
if (!poll_state_synchronize_rcu_full(&bnode->gp_snap))
|
||
break;
|
||
|
||
atomic_sub(bnode->nr_records, &krcp->bulk_count[i]);
|
||
list_move(&bnode->list, &bulk_ready[i]);
|
||
}
|
||
}
|
||
|
||
if (krcp->head && poll_state_synchronize_rcu(krcp->head_gp_snap)) {
|
||
head_ready = krcp->head;
|
||
atomic_set(&krcp->head_count, 0);
|
||
WRITE_ONCE(krcp->head, NULL);
|
||
}
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
|
||
for (i = 0; i < FREE_N_CHANNELS; i++) {
|
||
list_for_each_entry_safe(bnode, n, &bulk_ready[i], list)
|
||
kvfree_rcu_bulk(krcp, bnode, i);
|
||
}
|
||
|
||
if (head_ready)
|
||
kvfree_rcu_list(head_ready);
|
||
}
|
||
|
||
/*
|
||
* This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
|
||
*/
|
||
static void kfree_rcu_monitor(struct work_struct *work)
|
||
{
|
||
struct kfree_rcu_cpu *krcp = container_of(work,
|
||
struct kfree_rcu_cpu, monitor_work.work);
|
||
unsigned long flags;
|
||
int i, j;
|
||
|
||
// Drain ready for reclaim.
|
||
kvfree_rcu_drain_ready(krcp);
|
||
|
||
raw_spin_lock_irqsave(&krcp->lock, flags);
|
||
|
||
// Attempt to start a new batch.
|
||
for (i = 0; i < KFREE_N_BATCHES; i++) {
|
||
struct kfree_rcu_cpu_work *krwp = &(krcp->krw_arr[i]);
|
||
|
||
// Try to detach bulk_head or head and attach it, only when
|
||
// all channels are free. Any channel is not free means at krwp
|
||
// there is on-going rcu work to handle krwp's free business.
|
||
if (need_wait_for_krwp_work(krwp))
|
||
continue;
|
||
|
||
// kvfree_rcu_drain_ready() might handle this krcp, if so give up.
|
||
if (need_offload_krc(krcp)) {
|
||
// Channel 1 corresponds to the SLAB-pointer bulk path.
|
||
// Channel 2 corresponds to vmalloc-pointer bulk path.
|
||
for (j = 0; j < FREE_N_CHANNELS; j++) {
|
||
if (list_empty(&krwp->bulk_head_free[j])) {
|
||
atomic_set(&krcp->bulk_count[j], 0);
|
||
list_replace_init(&krcp->bulk_head[j],
|
||
&krwp->bulk_head_free[j]);
|
||
}
|
||
}
|
||
|
||
// Channel 3 corresponds to both SLAB and vmalloc
|
||
// objects queued on the linked list.
|
||
if (!krwp->head_free) {
|
||
krwp->head_free = krcp->head;
|
||
get_state_synchronize_rcu_full(&krwp->head_free_gp_snap);
|
||
atomic_set(&krcp->head_count, 0);
|
||
WRITE_ONCE(krcp->head, NULL);
|
||
}
|
||
|
||
// One work is per one batch, so there are three
|
||
// "free channels", the batch can handle. It can
|
||
// be that the work is in the pending state when
|
||
// channels have been detached following by each
|
||
// other.
|
||
queue_rcu_work(system_wq, &krwp->rcu_work);
|
||
}
|
||
}
|
||
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
|
||
// If there is nothing to detach, it means that our job is
|
||
// successfully done here. In case of having at least one
|
||
// of the channels that is still busy we should rearm the
|
||
// work to repeat an attempt. Because previous batches are
|
||
// still in progress.
|
||
if (need_offload_krc(krcp))
|
||
schedule_delayed_monitor_work(krcp);
|
||
}
|
||
|
||
static enum hrtimer_restart
|
||
schedule_page_work_fn(struct hrtimer *t)
|
||
{
|
||
struct kfree_rcu_cpu *krcp =
|
||
container_of(t, struct kfree_rcu_cpu, hrtimer);
|
||
|
||
queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0);
|
||
return HRTIMER_NORESTART;
|
||
}
|
||
|
||
static void fill_page_cache_func(struct work_struct *work)
|
||
{
|
||
struct kvfree_rcu_bulk_data *bnode;
|
||
struct kfree_rcu_cpu *krcp =
|
||
container_of(work, struct kfree_rcu_cpu,
|
||
page_cache_work.work);
|
||
unsigned long flags;
|
||
int nr_pages;
|
||
bool pushed;
|
||
int i;
|
||
|
||
nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ?
|
||
1 : rcu_min_cached_objs;
|
||
|
||
for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) {
|
||
bnode = (struct kvfree_rcu_bulk_data *)
|
||
__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
|
||
|
||
if (!bnode)
|
||
break;
|
||
|
||
raw_spin_lock_irqsave(&krcp->lock, flags);
|
||
pushed = put_cached_bnode(krcp, bnode);
|
||
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
||
|
||
if (!pushed) {
|
||
free_page((unsigned long) bnode);
|
||
break;
|
||
}
|
||
}
|
||
|
||
atomic_set(&krcp->work_in_progress, 0);
|
||
atomic_set(&krcp->backoff_page_cache_fill, 0);
|
||
}
|
||
|
||
static void
|
||
run_page_cache_worker(struct kfree_rcu_cpu *krcp)
|
||
{
|
||
// If cache disabled, bail out.
|
||
if (!rcu_min_cached_objs)
|
||
return;
|
||
|
||
if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
|
||
!atomic_xchg(&krcp->work_in_progress, 1)) {
|
||
if (atomic_read(&krcp->backoff_page_cache_fill)) {
|
||
queue_delayed_work(system_wq,
|
||
&krcp->page_cache_work,
|
||
msecs_to_jiffies(rcu_delay_page_cache_fill_msec));
|
||
} else {
|
||
hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
||
krcp->hrtimer.function = schedule_page_work_fn;
|
||
hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
|
||
}
|
||
}
|
||
}
|
||
|
||
// Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock()
|
||
// state specified by flags. If can_alloc is true, the caller must
|
||
// be schedulable and not be holding any locks or mutexes that might be
|
||
// acquired by the memory allocator or anything that it might invoke.
|
||
// Returns true if ptr was successfully recorded, else the caller must
|
||
// use a fallback.
|
||
static inline bool
|
||
add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
|
||
unsigned long *flags, void *ptr, bool can_alloc)
|
||
{
|
||
struct kvfree_rcu_bulk_data *bnode;
|
||
int idx;
|
||
|
||
*krcp = krc_this_cpu_lock(flags);
|
||
if (unlikely(!(*krcp)->initialized))
|
||
return false;
|
||
|
||
idx = !!is_vmalloc_addr(ptr);
|
||
bnode = list_first_entry_or_null(&(*krcp)->bulk_head[idx],
|
||
struct kvfree_rcu_bulk_data, list);
|
||
|
||
/* Check if a new block is required. */
|
||
if (!bnode || bnode->nr_records == KVFREE_BULK_MAX_ENTR) {
|
||
bnode = get_cached_bnode(*krcp);
|
||
if (!bnode && can_alloc) {
|
||
krc_this_cpu_unlock(*krcp, *flags);
|
||
|
||
// __GFP_NORETRY - allows a light-weight direct reclaim
|
||
// what is OK from minimizing of fallback hitting point of
|
||
// view. Apart of that it forbids any OOM invoking what is
|
||
// also beneficial since we are about to release memory soon.
|
||
//
|
||
// __GFP_NOMEMALLOC - prevents from consuming of all the
|
||
// memory reserves. Please note we have a fallback path.
|
||
//
|
||
// __GFP_NOWARN - it is supposed that an allocation can
|
||
// be failed under low memory or high memory pressure
|
||
// scenarios.
|
||
bnode = (struct kvfree_rcu_bulk_data *)
|
||
__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
|
||
raw_spin_lock_irqsave(&(*krcp)->lock, *flags);
|
||
}
|
||
|
||
if (!bnode)
|
||
return false;
|
||
|
||
// Initialize the new block and attach it.
|
||
bnode->nr_records = 0;
|
||
list_add(&bnode->list, &(*krcp)->bulk_head[idx]);
|
||
}
|
||
|
||
// Finally insert and update the GP for this page.
|
||
bnode->records[bnode->nr_records++] = ptr;
|
||
get_state_synchronize_rcu_full(&bnode->gp_snap);
|
||
atomic_inc(&(*krcp)->bulk_count[idx]);
|
||
|
||
return true;
|
||
}
|
||
|
||
/*
|
||
* Queue a request for lazy invocation of the appropriate free routine
|
||
* after a grace period. Please note that three paths are maintained,
|
||
* two for the common case using arrays of pointers and a third one that
|
||
* is used only when the main paths cannot be used, for example, due to
|
||
* memory pressure.
|
||
*
|
||
* Each kvfree_call_rcu() request is added to a batch. The batch will be drained
|
||
* every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will
|
||
* be free'd in workqueue context. This allows us to: batch requests together to
|
||
* reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load.
|
||
*/
|
||
void kvfree_call_rcu(struct rcu_head *head, void *ptr)
|
||
{
|
||
unsigned long flags;
|
||
struct kfree_rcu_cpu *krcp;
|
||
bool success;
|
||
|
||
/*
|
||
* Please note there is a limitation for the head-less
|
||
* variant, that is why there is a clear rule for such
|
||
* objects: it can be used from might_sleep() context
|
||
* only. For other places please embed an rcu_head to
|
||
* your data.
|
||
*/
|
||
if (!head)
|
||
might_sleep();
|
||
|
||
// Queue the object but don't yet schedule the batch.
|
||
if (debug_rcu_head_queue(ptr)) {
|
||
// Probable double kfree_rcu(), just leak.
|
||
WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
|
||
__func__, head);
|
||
|
||
// Mark as success and leave.
|
||
return;
|
||
}
|
||
|
||
kasan_record_aux_stack_noalloc(ptr);
|
||
success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
|
||
if (!success) {
|
||
run_page_cache_worker(krcp);
|
||
|
||
if (head == NULL)
|
||
// Inline if kvfree_rcu(one_arg) call.
|
||
goto unlock_return;
|
||
|
||
head->func = ptr;
|
||
head->next = krcp->head;
|
||
WRITE_ONCE(krcp->head, head);
|
||
atomic_inc(&krcp->head_count);
|
||
|
||
// Take a snapshot for this krcp.
|
||
krcp->head_gp_snap = get_state_synchronize_rcu();
|
||
success = true;
|
||
}
|
||
|
||
/*
|
||
* The kvfree_rcu() caller considers the pointer freed at this point
|
||
* and likely removes any references to it. Since the actual slab
|
||
* freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore
|
||
* this object (no scanning or false positives reporting).
|
||
*/
|
||
kmemleak_ignore(ptr);
|
||
|
||
// Set timer to drain after KFREE_DRAIN_JIFFIES.
|
||
if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
|
||
schedule_delayed_monitor_work(krcp);
|
||
|
||
unlock_return:
|
||
krc_this_cpu_unlock(krcp, flags);
|
||
|
||
/*
|
||
* Inline kvfree() after synchronize_rcu(). We can do
|
||
* it from might_sleep() context only, so the current
|
||
* CPU can pass the QS state.
|
||
*/
|
||
if (!success) {
|
||
debug_rcu_head_unqueue((struct rcu_head *) ptr);
|
||
synchronize_rcu();
|
||
kvfree(ptr);
|
||
}
|
||
}
|
||
EXPORT_SYMBOL_GPL(kvfree_call_rcu);
|
||
|
||
static unsigned long
|
||
kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
|
||
{
|
||
int cpu;
|
||
unsigned long count = 0;
|
||
|
||
/* Snapshot count of all CPUs */
|
||
for_each_possible_cpu(cpu) {
|
||
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
||
|
||
count += krc_count(krcp);
|
||
count += READ_ONCE(krcp->nr_bkv_objs);
|
||
atomic_set(&krcp->backoff_page_cache_fill, 1);
|
||
}
|
||
|
||
return count == 0 ? SHRINK_EMPTY : count;
|
||
}
|
||
|
||
static unsigned long
|
||
kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
|
||
{
|
||
int cpu, freed = 0;
|
||
|
||
for_each_possible_cpu(cpu) {
|
||
int count;
|
||
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
||
|
||
count = krc_count(krcp);
|
||
count += drain_page_cache(krcp);
|
||
kfree_rcu_monitor(&krcp->monitor_work.work);
|
||
|
||
sc->nr_to_scan -= count;
|
||
freed += count;
|
||
|
||
if (sc->nr_to_scan <= 0)
|
||
break;
|
||
}
|
||
|
||
return freed == 0 ? SHRINK_STOP : freed;
|
||
}
|
||
|
||
void __init kfree_rcu_scheduler_running(void)
|
||
{
|
||
int cpu;
|
||
|
||
for_each_possible_cpu(cpu) {
|
||
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
||
|
||
if (need_offload_krc(krcp))
|
||
schedule_delayed_monitor_work(krcp);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* During early boot, any blocking grace-period wait automatically
|
||
* implies a grace period.
|
||
*
|
||
* Later on, this could in theory be the case for kernels built with
|
||
* CONFIG_SMP=y && CONFIG_PREEMPTION=y running on a single CPU, but this
|
||
* is not a common case. Furthermore, this optimization would cause
|
||
* the rcu_gp_oldstate structure to expand by 50%, so this potential
|
||
* grace-period optimization is ignored once the scheduler is running.
|
||
*/
|
||
static int rcu_blocking_is_gp(void)
|
||
{
|
||
if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE) {
|
||
might_sleep();
|
||
return false;
|
||
}
|
||
return true;
|
||
}
|
||
|
||
/**
|
||
* synchronize_rcu - wait until a grace period has elapsed.
|
||
*
|
||
* Control will return to the caller some time after a full grace
|
||
* period has elapsed, in other words after all currently executing RCU
|
||
* read-side critical sections have completed. Note, however, that
|
||
* upon return from synchronize_rcu(), the caller might well be executing
|
||
* concurrently with new RCU read-side critical sections that began while
|
||
* synchronize_rcu() was waiting.
|
||
*
|
||
* RCU read-side critical sections are delimited by rcu_read_lock()
|
||
* and rcu_read_unlock(), and may be nested. In addition, but only in
|
||
* v5.0 and later, regions of code across which interrupts, preemption,
|
||
* or softirqs have been disabled also serve as RCU read-side critical
|
||
* sections. This includes hardware interrupt handlers, softirq handlers,
|
||
* and NMI handlers.
|
||
*
|
||
* Note that this guarantee implies further memory-ordering guarantees.
|
||
* On systems with more than one CPU, when synchronize_rcu() returns,
|
||
* each CPU is guaranteed to have executed a full memory barrier since
|
||
* the end of its last RCU read-side critical section whose beginning
|
||
* preceded the call to synchronize_rcu(). In addition, each CPU having
|
||
* an RCU read-side critical section that extends beyond the return from
|
||
* synchronize_rcu() is guaranteed to have executed a full memory barrier
|
||
* after the beginning of synchronize_rcu() and before the beginning of
|
||
* that RCU read-side critical section. Note that these guarantees include
|
||
* CPUs that are offline, idle, or executing in user mode, as well as CPUs
|
||
* that are executing in the kernel.
|
||
*
|
||
* Furthermore, if CPU A invoked synchronize_rcu(), which returned
|
||
* to its caller on CPU B, then both CPU A and CPU B are guaranteed
|
||
* to have executed a full memory barrier during the execution of
|
||
* synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but
|
||
* again only if the system has more than one CPU).
|
||
*
|
||
* Implementation of these memory-ordering guarantees is described here:
|
||
* Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst.
|
||
*/
|
||
void synchronize_rcu(void)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_node *rnp;
|
||
|
||
RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
|
||
lock_is_held(&rcu_lock_map) ||
|
||
lock_is_held(&rcu_sched_lock_map),
|
||
"Illegal synchronize_rcu() in RCU read-side critical section");
|
||
if (!rcu_blocking_is_gp()) {
|
||
if (rcu_gp_is_expedited())
|
||
synchronize_rcu_expedited();
|
||
else
|
||
wait_rcu_gp(call_rcu_hurry);
|
||
return;
|
||
}
|
||
|
||
// Context allows vacuous grace periods.
|
||
// Note well that this code runs with !PREEMPT && !SMP.
|
||
// In addition, all code that advances grace periods runs at
|
||
// process level. Therefore, this normal GP overlaps with other
|
||
// normal GPs only by being fully nested within them, which allows
|
||
// reuse of ->gp_seq_polled_snap.
|
||
rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_snap);
|
||
rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_snap);
|
||
|
||
// Update the normal grace-period counters to record
|
||
// this grace period, but only those used by the boot CPU.
|
||
// The rcu_scheduler_starting() will take care of the rest of
|
||
// these counters.
|
||
local_irq_save(flags);
|
||
WARN_ON_ONCE(num_online_cpus() > 1);
|
||
rcu_state.gp_seq += (1 << RCU_SEQ_CTR_SHIFT);
|
||
for (rnp = this_cpu_ptr(&rcu_data)->mynode; rnp; rnp = rnp->parent)
|
||
rnp->gp_seq_needed = rnp->gp_seq = rcu_state.gp_seq;
|
||
local_irq_restore(flags);
|
||
}
|
||
EXPORT_SYMBOL_GPL(synchronize_rcu);
|
||
|
||
/**
|
||
* get_completed_synchronize_rcu_full - Return a full pre-completed polled state cookie
|
||
* @rgosp: Place to put state cookie
|
||
*
|
||
* Stores into @rgosp a value that will always be treated by functions
|
||
* like poll_state_synchronize_rcu_full() as a cookie whose grace period
|
||
* has already completed.
|
||
*/
|
||
void get_completed_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
|
||
{
|
||
rgosp->rgos_norm = RCU_GET_STATE_COMPLETED;
|
||
rgosp->rgos_exp = RCU_GET_STATE_COMPLETED;
|
||
}
|
||
EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu_full);
|
||
|
||
/**
|
||
* get_state_synchronize_rcu - Snapshot current RCU state
|
||
*
|
||
* Returns a cookie that is used by a later call to cond_synchronize_rcu()
|
||
* or poll_state_synchronize_rcu() to determine whether or not a full
|
||
* grace period has elapsed in the meantime.
|
||
*/
|
||
unsigned long get_state_synchronize_rcu(void)
|
||
{
|
||
/*
|
||
* Any prior manipulation of RCU-protected data must happen
|
||
* before the load from ->gp_seq.
|
||
*/
|
||
smp_mb(); /* ^^^ */
|
||
return rcu_seq_snap(&rcu_state.gp_seq_polled);
|
||
}
|
||
EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
|
||
|
||
/**
|
||
* get_state_synchronize_rcu_full - Snapshot RCU state, both normal and expedited
|
||
* @rgosp: location to place combined normal/expedited grace-period state
|
||
*
|
||
* Places the normal and expedited grace-period states in @rgosp. This
|
||
* state value can be passed to a later call to cond_synchronize_rcu_full()
|
||
* or poll_state_synchronize_rcu_full() to determine whether or not a
|
||
* grace period (whether normal or expedited) has elapsed in the meantime.
|
||
* The rcu_gp_oldstate structure takes up twice the memory of an unsigned
|
||
* long, but is guaranteed to see all grace periods. In contrast, the
|
||
* combined state occupies less memory, but can sometimes fail to take
|
||
* grace periods into account.
|
||
*
|
||
* This does not guarantee that the needed grace period will actually
|
||
* start.
|
||
*/
|
||
void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
|
||
{
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
/*
|
||
* Any prior manipulation of RCU-protected data must happen
|
||
* before the loads from ->gp_seq and ->expedited_sequence.
|
||
*/
|
||
smp_mb(); /* ^^^ */
|
||
rgosp->rgos_norm = rcu_seq_snap(&rnp->gp_seq);
|
||
rgosp->rgos_exp = rcu_seq_snap(&rcu_state.expedited_sequence);
|
||
}
|
||
EXPORT_SYMBOL_GPL(get_state_synchronize_rcu_full);
|
||
|
||
/*
|
||
* Helper function for start_poll_synchronize_rcu() and
|
||
* start_poll_synchronize_rcu_full().
|
||
*/
|
||
static void start_poll_synchronize_rcu_common(void)
|
||
{
|
||
unsigned long flags;
|
||
bool needwake;
|
||
struct rcu_data *rdp;
|
||
struct rcu_node *rnp;
|
||
|
||
lockdep_assert_irqs_enabled();
|
||
local_irq_save(flags);
|
||
rdp = this_cpu_ptr(&rcu_data);
|
||
rnp = rdp->mynode;
|
||
raw_spin_lock_rcu_node(rnp); // irqs already disabled.
|
||
// Note it is possible for a grace period to have elapsed between
|
||
// the above call to get_state_synchronize_rcu() and the below call
|
||
// to rcu_seq_snap. This is OK, the worst that happens is that we
|
||
// get a grace period that no one needed. These accesses are ordered
|
||
// by smp_mb(), and we are accessing them in the opposite order
|
||
// from which they are updated at grace-period start, as required.
|
||
needwake = rcu_start_this_gp(rnp, rdp, rcu_seq_snap(&rcu_state.gp_seq));
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
if (needwake)
|
||
rcu_gp_kthread_wake();
|
||
}
|
||
|
||
/**
|
||
* start_poll_synchronize_rcu - Snapshot and start RCU grace period
|
||
*
|
||
* Returns a cookie that is used by a later call to cond_synchronize_rcu()
|
||
* or poll_state_synchronize_rcu() to determine whether or not a full
|
||
* grace period has elapsed in the meantime. If the needed grace period
|
||
* is not already slated to start, notifies RCU core of the need for that
|
||
* grace period.
|
||
*
|
||
* Interrupts must be enabled for the case where it is necessary to awaken
|
||
* the grace-period kthread.
|
||
*/
|
||
unsigned long start_poll_synchronize_rcu(void)
|
||
{
|
||
unsigned long gp_seq = get_state_synchronize_rcu();
|
||
|
||
start_poll_synchronize_rcu_common();
|
||
return gp_seq;
|
||
}
|
||
EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu);
|
||
|
||
/**
|
||
* start_poll_synchronize_rcu_full - Take a full snapshot and start RCU grace period
|
||
* @rgosp: value from get_state_synchronize_rcu_full() or start_poll_synchronize_rcu_full()
|
||
*
|
||
* Places the normal and expedited grace-period states in *@rgos. This
|
||
* state value can be passed to a later call to cond_synchronize_rcu_full()
|
||
* or poll_state_synchronize_rcu_full() to determine whether or not a
|
||
* grace period (whether normal or expedited) has elapsed in the meantime.
|
||
* If the needed grace period is not already slated to start, notifies
|
||
* RCU core of the need for that grace period.
|
||
*
|
||
* Interrupts must be enabled for the case where it is necessary to awaken
|
||
* the grace-period kthread.
|
||
*/
|
||
void start_poll_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
|
||
{
|
||
get_state_synchronize_rcu_full(rgosp);
|
||
|
||
start_poll_synchronize_rcu_common();
|
||
}
|
||
EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_full);
|
||
|
||
/**
|
||
* poll_state_synchronize_rcu - Has the specified RCU grace period completed?
|
||
* @oldstate: value from get_state_synchronize_rcu() or start_poll_synchronize_rcu()
|
||
*
|
||
* If a full RCU grace period has elapsed since the earlier call from
|
||
* which @oldstate was obtained, return @true, otherwise return @false.
|
||
* If @false is returned, it is the caller's responsibility to invoke this
|
||
* function later on until it does return @true. Alternatively, the caller
|
||
* can explicitly wait for a grace period, for example, by passing @oldstate
|
||
* to either cond_synchronize_rcu() or cond_synchronize_rcu_expedited()
|
||
* on the one hand or by directly invoking either synchronize_rcu() or
|
||
* synchronize_rcu_expedited() on the other.
|
||
*
|
||
* Yes, this function does not take counter wrap into account.
|
||
* But counter wrap is harmless. If the counter wraps, we have waited for
|
||
* more than a billion grace periods (and way more on a 64-bit system!).
|
||
* Those needing to keep old state values for very long time periods
|
||
* (many hours even on 32-bit systems) should check them occasionally and
|
||
* either refresh them or set a flag indicating that the grace period has
|
||
* completed. Alternatively, they can use get_completed_synchronize_rcu()
|
||
* to get a guaranteed-completed grace-period state.
|
||
*
|
||
* In addition, because oldstate compresses the grace-period state for
|
||
* both normal and expedited grace periods into a single unsigned long,
|
||
* it can miss a grace period when synchronize_rcu() runs concurrently
|
||
* with synchronize_rcu_expedited(). If this is unacceptable, please
|
||
* instead use the _full() variant of these polling APIs.
|
||
*
|
||
* This function provides the same memory-ordering guarantees that
|
||
* would be provided by a synchronize_rcu() that was invoked at the call
|
||
* to the function that provided @oldstate, and that returned at the end
|
||
* of this function.
|
||
*/
|
||
bool poll_state_synchronize_rcu(unsigned long oldstate)
|
||
{
|
||
if (oldstate == RCU_GET_STATE_COMPLETED ||
|
||
rcu_seq_done_exact(&rcu_state.gp_seq_polled, oldstate)) {
|
||
smp_mb(); /* Ensure GP ends before subsequent accesses. */
|
||
return true;
|
||
}
|
||
return false;
|
||
}
|
||
EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
|
||
|
||
/**
|
||
* poll_state_synchronize_rcu_full - Has the specified RCU grace period completed?
|
||
* @rgosp: value from get_state_synchronize_rcu_full() or start_poll_synchronize_rcu_full()
|
||
*
|
||
* If a full RCU grace period has elapsed since the earlier call from
|
||
* which *rgosp was obtained, return @true, otherwise return @false.
|
||
* If @false is returned, it is the caller's responsibility to invoke this
|
||
* function later on until it does return @true. Alternatively, the caller
|
||
* can explicitly wait for a grace period, for example, by passing @rgosp
|
||
* to cond_synchronize_rcu() or by directly invoking synchronize_rcu().
|
||
*
|
||
* Yes, this function does not take counter wrap into account.
|
||
* But counter wrap is harmless. If the counter wraps, we have waited
|
||
* for more than a billion grace periods (and way more on a 64-bit
|
||
* system!). Those needing to keep rcu_gp_oldstate values for very
|
||
* long time periods (many hours even on 32-bit systems) should check
|
||
* them occasionally and either refresh them or set a flag indicating
|
||
* that the grace period has completed. Alternatively, they can use
|
||
* get_completed_synchronize_rcu_full() to get a guaranteed-completed
|
||
* grace-period state.
|
||
*
|
||
* This function provides the same memory-ordering guarantees that would
|
||
* be provided by a synchronize_rcu() that was invoked at the call to
|
||
* the function that provided @rgosp, and that returned at the end of this
|
||
* function. And this guarantee requires that the root rcu_node structure's
|
||
* ->gp_seq field be checked instead of that of the rcu_state structure.
|
||
* The problem is that the just-ending grace-period's callbacks can be
|
||
* invoked between the time that the root rcu_node structure's ->gp_seq
|
||
* field is updated and the time that the rcu_state structure's ->gp_seq
|
||
* field is updated. Therefore, if a single synchronize_rcu() is to
|
||
* cause a subsequent poll_state_synchronize_rcu_full() to return @true,
|
||
* then the root rcu_node structure is the one that needs to be polled.
|
||
*/
|
||
bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
|
||
{
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
smp_mb(); // Order against root rcu_node structure grace-period cleanup.
|
||
if (rgosp->rgos_norm == RCU_GET_STATE_COMPLETED ||
|
||
rcu_seq_done_exact(&rnp->gp_seq, rgosp->rgos_norm) ||
|
||
rgosp->rgos_exp == RCU_GET_STATE_COMPLETED ||
|
||
rcu_seq_done_exact(&rcu_state.expedited_sequence, rgosp->rgos_exp)) {
|
||
smp_mb(); /* Ensure GP ends before subsequent accesses. */
|
||
return true;
|
||
}
|
||
return false;
|
||
}
|
||
EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu_full);
|
||
|
||
/**
|
||
* cond_synchronize_rcu - Conditionally wait for an RCU grace period
|
||
* @oldstate: value from get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or start_poll_synchronize_rcu_expedited()
|
||
*
|
||
* If a full RCU grace period has elapsed since the earlier call to
|
||
* get_state_synchronize_rcu() or start_poll_synchronize_rcu(), just return.
|
||
* Otherwise, invoke synchronize_rcu() to wait for a full grace period.
|
||
*
|
||
* Yes, this function does not take counter wrap into account.
|
||
* But counter wrap is harmless. If the counter wraps, we have waited for
|
||
* more than 2 billion grace periods (and way more on a 64-bit system!),
|
||
* so waiting for a couple of additional grace periods should be just fine.
|
||
*
|
||
* This function provides the same memory-ordering guarantees that
|
||
* would be provided by a synchronize_rcu() that was invoked at the call
|
||
* to the function that provided @oldstate and that returned at the end
|
||
* of this function.
|
||
*/
|
||
void cond_synchronize_rcu(unsigned long oldstate)
|
||
{
|
||
if (!poll_state_synchronize_rcu(oldstate))
|
||
synchronize_rcu();
|
||
}
|
||
EXPORT_SYMBOL_GPL(cond_synchronize_rcu);
|
||
|
||
/**
|
||
* cond_synchronize_rcu_full - Conditionally wait for an RCU grace period
|
||
* @rgosp: value from get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(), or start_poll_synchronize_rcu_expedited_full()
|
||
*
|
||
* If a full RCU grace period has elapsed since the call to
|
||
* get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(),
|
||
* or start_poll_synchronize_rcu_expedited_full() from which @rgosp was
|
||
* obtained, just return. Otherwise, invoke synchronize_rcu() to wait
|
||
* for a full grace period.
|
||
*
|
||
* Yes, this function does not take counter wrap into account.
|
||
* But counter wrap is harmless. If the counter wraps, we have waited for
|
||
* more than 2 billion grace periods (and way more on a 64-bit system!),
|
||
* so waiting for a couple of additional grace periods should be just fine.
|
||
*
|
||
* This function provides the same memory-ordering guarantees that
|
||
* would be provided by a synchronize_rcu() that was invoked at the call
|
||
* to the function that provided @rgosp and that returned at the end of
|
||
* this function.
|
||
*/
|
||
void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
|
||
{
|
||
if (!poll_state_synchronize_rcu_full(rgosp))
|
||
synchronize_rcu();
|
||
}
|
||
EXPORT_SYMBOL_GPL(cond_synchronize_rcu_full);
|
||
|
||
/*
|
||
* Check to see if there is any immediate RCU-related work to be done by
|
||
* the current CPU, returning 1 if so and zero otherwise. The checks are
|
||
* in order of increasing expense: checks that can be carried out against
|
||
* CPU-local state are performed first. However, we must check for CPU
|
||
* stalls first, else we might not get a chance.
|
||
*/
|
||
static int rcu_pending(int user)
|
||
{
|
||
bool gp_in_progress;
|
||
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
||
struct rcu_node *rnp = rdp->mynode;
|
||
|
||
lockdep_assert_irqs_disabled();
|
||
|
||
/* Check for CPU stalls, if enabled. */
|
||
check_cpu_stall(rdp);
|
||
|
||
/* Does this CPU need a deferred NOCB wakeup? */
|
||
if (rcu_nocb_need_deferred_wakeup(rdp, RCU_NOCB_WAKE))
|
||
return 1;
|
||
|
||
/* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */
|
||
if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu())
|
||
return 0;
|
||
|
||
/* Is the RCU core waiting for a quiescent state from this CPU? */
|
||
gp_in_progress = rcu_gp_in_progress();
|
||
if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm && gp_in_progress)
|
||
return 1;
|
||
|
||
/* Does this CPU have callbacks ready to invoke? */
|
||
if (!rcu_rdp_is_offloaded(rdp) &&
|
||
rcu_segcblist_ready_cbs(&rdp->cblist))
|
||
return 1;
|
||
|
||
/* Has RCU gone idle with this CPU needing another grace period? */
|
||
if (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) &&
|
||
!rcu_rdp_is_offloaded(rdp) &&
|
||
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
|
||
return 1;
|
||
|
||
/* Have RCU grace period completed or started? */
|
||
if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq ||
|
||
unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */
|
||
return 1;
|
||
|
||
/* nothing to do */
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Helper function for rcu_barrier() tracing. If tracing is disabled,
|
||
* the compiler is expected to optimize this away.
|
||
*/
|
||
static void rcu_barrier_trace(const char *s, int cpu, unsigned long done)
|
||
{
|
||
trace_rcu_barrier(rcu_state.name, s, cpu,
|
||
atomic_read(&rcu_state.barrier_cpu_count), done);
|
||
}
|
||
|
||
/*
|
||
* RCU callback function for rcu_barrier(). If we are last, wake
|
||
* up the task executing rcu_barrier().
|
||
*
|
||
* Note that the value of rcu_state.barrier_sequence must be captured
|
||
* before the atomic_dec_and_test(). Otherwise, if this CPU is not last,
|
||
* other CPUs might count the value down to zero before this CPU gets
|
||
* around to invoking rcu_barrier_trace(), which might result in bogus
|
||
* data from the next instance of rcu_barrier().
|
||
*/
|
||
static void rcu_barrier_callback(struct rcu_head *rhp)
|
||
{
|
||
unsigned long __maybe_unused s = rcu_state.barrier_sequence;
|
||
|
||
if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) {
|
||
rcu_barrier_trace(TPS("LastCB"), -1, s);
|
||
complete(&rcu_state.barrier_completion);
|
||
} else {
|
||
rcu_barrier_trace(TPS("CB"), -1, s);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* If needed, entrain an rcu_barrier() callback on rdp->cblist.
|
||
*/
|
||
static void rcu_barrier_entrain(struct rcu_data *rdp)
|
||
{
|
||
unsigned long gseq = READ_ONCE(rcu_state.barrier_sequence);
|
||
unsigned long lseq = READ_ONCE(rdp->barrier_seq_snap);
|
||
bool wake_nocb = false;
|
||
bool was_alldone = false;
|
||
|
||
lockdep_assert_held(&rcu_state.barrier_lock);
|
||
if (rcu_seq_state(lseq) || !rcu_seq_state(gseq) || rcu_seq_ctr(lseq) != rcu_seq_ctr(gseq))
|
||
return;
|
||
rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence);
|
||
rdp->barrier_head.func = rcu_barrier_callback;
|
||
debug_rcu_head_queue(&rdp->barrier_head);
|
||
rcu_nocb_lock(rdp);
|
||
/*
|
||
* Flush bypass and wakeup rcuog if we add callbacks to an empty regular
|
||
* queue. This way we don't wait for bypass timer that can reach seconds
|
||
* if it's fully lazy.
|
||
*/
|
||
was_alldone = rcu_rdp_is_offloaded(rdp) && !rcu_segcblist_pend_cbs(&rdp->cblist);
|
||
WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies, false));
|
||
wake_nocb = was_alldone && rcu_segcblist_pend_cbs(&rdp->cblist);
|
||
if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head)) {
|
||
atomic_inc(&rcu_state.barrier_cpu_count);
|
||
} else {
|
||
debug_rcu_head_unqueue(&rdp->barrier_head);
|
||
rcu_barrier_trace(TPS("IRQNQ"), -1, rcu_state.barrier_sequence);
|
||
}
|
||
rcu_nocb_unlock(rdp);
|
||
if (wake_nocb)
|
||
wake_nocb_gp(rdp, false);
|
||
smp_store_release(&rdp->barrier_seq_snap, gseq);
|
||
}
|
||
|
||
/*
|
||
* Called with preemption disabled, and from cross-cpu IRQ context.
|
||
*/
|
||
static void rcu_barrier_handler(void *cpu_in)
|
||
{
|
||
uintptr_t cpu = (uintptr_t)cpu_in;
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
lockdep_assert_irqs_disabled();
|
||
WARN_ON_ONCE(cpu != rdp->cpu);
|
||
WARN_ON_ONCE(cpu != smp_processor_id());
|
||
raw_spin_lock(&rcu_state.barrier_lock);
|
||
rcu_barrier_entrain(rdp);
|
||
raw_spin_unlock(&rcu_state.barrier_lock);
|
||
}
|
||
|
||
/**
|
||
* rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
|
||
*
|
||
* Note that this primitive does not necessarily wait for an RCU grace period
|
||
* to complete. For example, if there are no RCU callbacks queued anywhere
|
||
* in the system, then rcu_barrier() is within its rights to return
|
||
* immediately, without waiting for anything, much less an RCU grace period.
|
||
*/
|
||
void rcu_barrier(void)
|
||
{
|
||
uintptr_t cpu;
|
||
unsigned long flags;
|
||
unsigned long gseq;
|
||
struct rcu_data *rdp;
|
||
unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
|
||
|
||
rcu_barrier_trace(TPS("Begin"), -1, s);
|
||
|
||
/* Take mutex to serialize concurrent rcu_barrier() requests. */
|
||
mutex_lock(&rcu_state.barrier_mutex);
|
||
|
||
/* Did someone else do our work for us? */
|
||
if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
|
||
rcu_barrier_trace(TPS("EarlyExit"), -1, rcu_state.barrier_sequence);
|
||
smp_mb(); /* caller's subsequent code after above check. */
|
||
mutex_unlock(&rcu_state.barrier_mutex);
|
||
return;
|
||
}
|
||
|
||
/* Mark the start of the barrier operation. */
|
||
raw_spin_lock_irqsave(&rcu_state.barrier_lock, flags);
|
||
rcu_seq_start(&rcu_state.barrier_sequence);
|
||
gseq = rcu_state.barrier_sequence;
|
||
rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence);
|
||
|
||
/*
|
||
* Initialize the count to two rather than to zero in order
|
||
* to avoid a too-soon return to zero in case of an immediate
|
||
* invocation of the just-enqueued callback (or preemption of
|
||
* this task). Exclude CPU-hotplug operations to ensure that no
|
||
* offline non-offloaded CPU has callbacks queued.
|
||
*/
|
||
init_completion(&rcu_state.barrier_completion);
|
||
atomic_set(&rcu_state.barrier_cpu_count, 2);
|
||
raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
|
||
|
||
/*
|
||
* Force each CPU with callbacks to register a new callback.
|
||
* When that callback is invoked, we will know that all of the
|
||
* corresponding CPU's preceding callbacks have been invoked.
|
||
*/
|
||
for_each_possible_cpu(cpu) {
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
retry:
|
||
if (smp_load_acquire(&rdp->barrier_seq_snap) == gseq)
|
||
continue;
|
||
raw_spin_lock_irqsave(&rcu_state.barrier_lock, flags);
|
||
if (!rcu_segcblist_n_cbs(&rdp->cblist)) {
|
||
WRITE_ONCE(rdp->barrier_seq_snap, gseq);
|
||
raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
|
||
rcu_barrier_trace(TPS("NQ"), cpu, rcu_state.barrier_sequence);
|
||
continue;
|
||
}
|
||
if (!rcu_rdp_cpu_online(rdp)) {
|
||
rcu_barrier_entrain(rdp);
|
||
WARN_ON_ONCE(READ_ONCE(rdp->barrier_seq_snap) != gseq);
|
||
raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
|
||
rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu, rcu_state.barrier_sequence);
|
||
continue;
|
||
}
|
||
raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
|
||
if (smp_call_function_single(cpu, rcu_barrier_handler, (void *)cpu, 1)) {
|
||
schedule_timeout_uninterruptible(1);
|
||
goto retry;
|
||
}
|
||
WARN_ON_ONCE(READ_ONCE(rdp->barrier_seq_snap) != gseq);
|
||
rcu_barrier_trace(TPS("OnlineQ"), cpu, rcu_state.barrier_sequence);
|
||
}
|
||
|
||
/*
|
||
* Now that we have an rcu_barrier_callback() callback on each
|
||
* CPU, and thus each counted, remove the initial count.
|
||
*/
|
||
if (atomic_sub_and_test(2, &rcu_state.barrier_cpu_count))
|
||
complete(&rcu_state.barrier_completion);
|
||
|
||
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
|
||
wait_for_completion(&rcu_state.barrier_completion);
|
||
|
||
/* Mark the end of the barrier operation. */
|
||
rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence);
|
||
rcu_seq_end(&rcu_state.barrier_sequence);
|
||
gseq = rcu_state.barrier_sequence;
|
||
for_each_possible_cpu(cpu) {
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
WRITE_ONCE(rdp->barrier_seq_snap, gseq);
|
||
}
|
||
|
||
/* Other rcu_barrier() invocations can now safely proceed. */
|
||
mutex_unlock(&rcu_state.barrier_mutex);
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_barrier);
|
||
|
||
static unsigned long rcu_barrier_last_throttle;
|
||
|
||
/**
|
||
* rcu_barrier_throttled - Do rcu_barrier(), but limit to one per second
|
||
*
|
||
* This can be thought of as guard rails around rcu_barrier() that
|
||
* permits unrestricted userspace use, at least assuming the hardware's
|
||
* try_cmpxchg() is robust. There will be at most one call per second to
|
||
* rcu_barrier() system-wide from use of this function, which means that
|
||
* callers might needlessly wait a second or three.
|
||
*
|
||
* This is intended for use by test suites to avoid OOM by flushing RCU
|
||
* callbacks from the previous test before starting the next. See the
|
||
* rcutree.do_rcu_barrier module parameter for more information.
|
||
*
|
||
* Why not simply make rcu_barrier() more scalable? That might be
|
||
* the eventual endpoint, but let's keep it simple for the time being.
|
||
* Note that the module parameter infrastructure serializes calls to a
|
||
* given .set() function, but should concurrent .set() invocation ever be
|
||
* possible, we are ready!
|
||
*/
|
||
static void rcu_barrier_throttled(void)
|
||
{
|
||
unsigned long j = jiffies;
|
||
unsigned long old = READ_ONCE(rcu_barrier_last_throttle);
|
||
unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
|
||
|
||
while (time_in_range(j, old, old + HZ / 16) ||
|
||
!try_cmpxchg(&rcu_barrier_last_throttle, &old, j)) {
|
||
schedule_timeout_idle(HZ / 16);
|
||
if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
|
||
smp_mb(); /* caller's subsequent code after above check. */
|
||
return;
|
||
}
|
||
j = jiffies;
|
||
old = READ_ONCE(rcu_barrier_last_throttle);
|
||
}
|
||
rcu_barrier();
|
||
}
|
||
|
||
/*
|
||
* Invoke rcu_barrier_throttled() when a rcutree.do_rcu_barrier
|
||
* request arrives. We insist on a true value to allow for possible
|
||
* future expansion.
|
||
*/
|
||
static int param_set_do_rcu_barrier(const char *val, const struct kernel_param *kp)
|
||
{
|
||
bool b;
|
||
int ret;
|
||
|
||
if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING)
|
||
return -EAGAIN;
|
||
ret = kstrtobool(val, &b);
|
||
if (!ret && b) {
|
||
atomic_inc((atomic_t *)kp->arg);
|
||
rcu_barrier_throttled();
|
||
atomic_dec((atomic_t *)kp->arg);
|
||
}
|
||
return ret;
|
||
}
|
||
|
||
/*
|
||
* Output the number of outstanding rcutree.do_rcu_barrier requests.
|
||
*/
|
||
static int param_get_do_rcu_barrier(char *buffer, const struct kernel_param *kp)
|
||
{
|
||
return sprintf(buffer, "%d\n", atomic_read((atomic_t *)kp->arg));
|
||
}
|
||
|
||
static const struct kernel_param_ops do_rcu_barrier_ops = {
|
||
.set = param_set_do_rcu_barrier,
|
||
.get = param_get_do_rcu_barrier,
|
||
};
|
||
static atomic_t do_rcu_barrier;
|
||
module_param_cb(do_rcu_barrier, &do_rcu_barrier_ops, &do_rcu_barrier, 0644);
|
||
|
||
/*
|
||
* Compute the mask of online CPUs for the specified rcu_node structure.
|
||
* This will not be stable unless the rcu_node structure's ->lock is
|
||
* held, but the bit corresponding to the current CPU will be stable
|
||
* in most contexts.
|
||
*/
|
||
static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
|
||
{
|
||
return READ_ONCE(rnp->qsmaskinitnext);
|
||
}
|
||
|
||
/*
|
||
* Is the CPU corresponding to the specified rcu_data structure online
|
||
* from RCU's perspective? This perspective is given by that structure's
|
||
* ->qsmaskinitnext field rather than by the global cpu_online_mask.
|
||
*/
|
||
static bool rcu_rdp_cpu_online(struct rcu_data *rdp)
|
||
{
|
||
return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode));
|
||
}
|
||
|
||
bool rcu_cpu_online(int cpu)
|
||
{
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
return rcu_rdp_cpu_online(rdp);
|
||
}
|
||
|
||
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
|
||
|
||
/*
|
||
* Is the current CPU online as far as RCU is concerned?
|
||
*
|
||
* Disable preemption to avoid false positives that could otherwise
|
||
* happen due to the current CPU number being sampled, this task being
|
||
* preempted, its old CPU being taken offline, resuming on some other CPU,
|
||
* then determining that its old CPU is now offline.
|
||
*
|
||
* Disable checking if in an NMI handler because we cannot safely
|
||
* report errors from NMI handlers anyway. In addition, it is OK to use
|
||
* RCU on an offline processor during initial boot, hence the check for
|
||
* rcu_scheduler_fully_active.
|
||
*/
|
||
bool rcu_lockdep_current_cpu_online(void)
|
||
{
|
||
struct rcu_data *rdp;
|
||
bool ret = false;
|
||
|
||
if (in_nmi() || !rcu_scheduler_fully_active)
|
||
return true;
|
||
preempt_disable_notrace();
|
||
rdp = this_cpu_ptr(&rcu_data);
|
||
/*
|
||
* Strictly, we care here about the case where the current CPU is
|
||
* in rcutree_report_cpu_starting() and thus has an excuse for rdp->grpmask
|
||
* not being up to date. So arch_spin_is_locked() might have a
|
||
* false positive if it's held by some *other* CPU, but that's
|
||
* OK because that just means a false *negative* on the warning.
|
||
*/
|
||
if (rcu_rdp_cpu_online(rdp) || arch_spin_is_locked(&rcu_state.ofl_lock))
|
||
ret = true;
|
||
preempt_enable_notrace();
|
||
return ret;
|
||
}
|
||
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
|
||
|
||
#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
|
||
|
||
// Has rcu_init() been invoked? This is used (for example) to determine
|
||
// whether spinlocks may be acquired safely.
|
||
static bool rcu_init_invoked(void)
|
||
{
|
||
return !!rcu_state.n_online_cpus;
|
||
}
|
||
|
||
/*
|
||
* All CPUs for the specified rcu_node structure have gone offline,
|
||
* and all tasks that were preempted within an RCU read-side critical
|
||
* section while running on one of those CPUs have since exited their RCU
|
||
* read-side critical section. Some other CPU is reporting this fact with
|
||
* the specified rcu_node structure's ->lock held and interrupts disabled.
|
||
* This function therefore goes up the tree of rcu_node structures,
|
||
* clearing the corresponding bits in the ->qsmaskinit fields. Note that
|
||
* the leaf rcu_node structure's ->qsmaskinit field has already been
|
||
* updated.
|
||
*
|
||
* This function does check that the specified rcu_node structure has
|
||
* all CPUs offline and no blocked tasks, so it is OK to invoke it
|
||
* prematurely. That said, invoking it after the fact will cost you
|
||
* a needless lock acquisition. So once it has done its work, don't
|
||
* invoke it again.
|
||
*/
|
||
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
|
||
{
|
||
long mask;
|
||
struct rcu_node *rnp = rnp_leaf;
|
||
|
||
raw_lockdep_assert_held_rcu_node(rnp_leaf);
|
||
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
|
||
WARN_ON_ONCE(rnp_leaf->qsmaskinit) ||
|
||
WARN_ON_ONCE(rcu_preempt_has_tasks(rnp_leaf)))
|
||
return;
|
||
for (;;) {
|
||
mask = rnp->grpmask;
|
||
rnp = rnp->parent;
|
||
if (!rnp)
|
||
break;
|
||
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
|
||
rnp->qsmaskinit &= ~mask;
|
||
/* Between grace periods, so better already be zero! */
|
||
WARN_ON_ONCE(rnp->qsmask);
|
||
if (rnp->qsmaskinit) {
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
/* irqs remain disabled. */
|
||
return;
|
||
}
|
||
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Propagate ->qsinitmask bits up the rcu_node tree to account for the
|
||
* first CPU in a given leaf rcu_node structure coming online. The caller
|
||
* must hold the corresponding leaf rcu_node ->lock with interrupts
|
||
* disabled.
|
||
*/
|
||
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
|
||
{
|
||
long mask;
|
||
long oldmask;
|
||
struct rcu_node *rnp = rnp_leaf;
|
||
|
||
raw_lockdep_assert_held_rcu_node(rnp_leaf);
|
||
WARN_ON_ONCE(rnp->wait_blkd_tasks);
|
||
for (;;) {
|
||
mask = rnp->grpmask;
|
||
rnp = rnp->parent;
|
||
if (rnp == NULL)
|
||
return;
|
||
raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */
|
||
oldmask = rnp->qsmaskinit;
|
||
rnp->qsmaskinit |= mask;
|
||
raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */
|
||
if (oldmask)
|
||
return;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Do boot-time initialization of a CPU's per-CPU RCU data.
|
||
*/
|
||
static void __init
|
||
rcu_boot_init_percpu_data(int cpu)
|
||
{
|
||
struct context_tracking *ct = this_cpu_ptr(&context_tracking);
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
/* Set up local state, ensuring consistent view of global state. */
|
||
rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
|
||
INIT_WORK(&rdp->strict_work, strict_work_handler);
|
||
WARN_ON_ONCE(ct->dynticks_nesting != 1);
|
||
WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)));
|
||
rdp->barrier_seq_snap = rcu_state.barrier_sequence;
|
||
rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
|
||
rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
|
||
rdp->rcu_onl_gp_seq = rcu_state.gp_seq;
|
||
rdp->rcu_onl_gp_flags = RCU_GP_CLEANED;
|
||
rdp->last_sched_clock = jiffies;
|
||
rdp->cpu = cpu;
|
||
rcu_boot_init_nocb_percpu_data(rdp);
|
||
}
|
||
|
||
/*
|
||
* Invoked early in the CPU-online process, when pretty much all services
|
||
* are available. The incoming CPU is not present.
|
||
*
|
||
* Initializes a CPU's per-CPU RCU data. Note that only one online or
|
||
* offline event can be happening at a given time. Note also that we can
|
||
* accept some slop in the rsp->gp_seq access due to the fact that this
|
||
* CPU cannot possibly have any non-offloaded RCU callbacks in flight yet.
|
||
* And any offloaded callbacks are being numbered elsewhere.
|
||
*/
|
||
int rcutree_prepare_cpu(unsigned int cpu)
|
||
{
|
||
unsigned long flags;
|
||
struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
struct rcu_node *rnp = rcu_get_root();
|
||
|
||
/* Set up local state, ensuring consistent view of global state. */
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
rdp->qlen_last_fqs_check = 0;
|
||
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
|
||
rdp->blimit = blimit;
|
||
ct->dynticks_nesting = 1; /* CPU not up, no tearing. */
|
||
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
||
|
||
/*
|
||
* Only non-NOCB CPUs that didn't have early-boot callbacks need to be
|
||
* (re-)initialized.
|
||
*/
|
||
if (!rcu_segcblist_is_enabled(&rdp->cblist))
|
||
rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */
|
||
|
||
/*
|
||
* Add CPU to leaf rcu_node pending-online bitmask. Any needed
|
||
* propagation up the rcu_node tree will happen at the beginning
|
||
* of the next grace period.
|
||
*/
|
||
rnp = rdp->mynode;
|
||
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
|
||
rdp->gp_seq = READ_ONCE(rnp->gp_seq);
|
||
rdp->gp_seq_needed = rdp->gp_seq;
|
||
rdp->cpu_no_qs.b.norm = true;
|
||
rdp->core_needs_qs = false;
|
||
rdp->rcu_iw_pending = false;
|
||
rdp->rcu_iw = IRQ_WORK_INIT_HARD(rcu_iw_handler);
|
||
rdp->rcu_iw_gp_seq = rdp->gp_seq - 1;
|
||
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl"));
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
rcu_spawn_one_boost_kthread(rnp);
|
||
rcu_spawn_cpu_nocb_kthread(cpu);
|
||
WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1);
|
||
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Update RCU priority boot kthread affinity for CPU-hotplug changes.
|
||
*/
|
||
static void rcutree_affinity_setting(unsigned int cpu, int outgoing)
|
||
{
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
rcu_boost_kthread_setaffinity(rdp->mynode, outgoing);
|
||
}
|
||
|
||
/*
|
||
* Has the specified (known valid) CPU ever been fully online?
|
||
*/
|
||
bool rcu_cpu_beenfullyonline(int cpu)
|
||
{
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
|
||
return smp_load_acquire(&rdp->beenonline);
|
||
}
|
||
|
||
/*
|
||
* Near the end of the CPU-online process. Pretty much all services
|
||
* enabled, and the CPU is now very much alive.
|
||
*/
|
||
int rcutree_online_cpu(unsigned int cpu)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_data *rdp;
|
||
struct rcu_node *rnp;
|
||
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
rnp = rdp->mynode;
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
rnp->ffmask |= rdp->grpmask;
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
|
||
return 0; /* Too early in boot for scheduler work. */
|
||
sync_sched_exp_online_cleanup(cpu);
|
||
rcutree_affinity_setting(cpu, -1);
|
||
|
||
// Stop-machine done, so allow nohz_full to disable tick.
|
||
tick_dep_clear(TICK_DEP_BIT_RCU);
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Mark the specified CPU as being online so that subsequent grace periods
|
||
* (both expedited and normal) will wait on it. Note that this means that
|
||
* incoming CPUs are not allowed to use RCU read-side critical sections
|
||
* until this function is called. Failing to observe this restriction
|
||
* will result in lockdep splats.
|
||
*
|
||
* Note that this function is special in that it is invoked directly
|
||
* from the incoming CPU rather than from the cpuhp_step mechanism.
|
||
* This is because this function must be invoked at a precise location.
|
||
* This incoming CPU must not have enabled interrupts yet.
|
||
*
|
||
* This mirrors the effects of rcutree_report_cpu_dead().
|
||
*/
|
||
void rcutree_report_cpu_starting(unsigned int cpu)
|
||
{
|
||
unsigned long mask;
|
||
struct rcu_data *rdp;
|
||
struct rcu_node *rnp;
|
||
bool newcpu;
|
||
|
||
lockdep_assert_irqs_disabled();
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
if (rdp->cpu_started)
|
||
return;
|
||
rdp->cpu_started = true;
|
||
|
||
rnp = rdp->mynode;
|
||
mask = rdp->grpmask;
|
||
arch_spin_lock(&rcu_state.ofl_lock);
|
||
rcu_dynticks_eqs_online();
|
||
raw_spin_lock(&rcu_state.barrier_lock);
|
||
raw_spin_lock_rcu_node(rnp);
|
||
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask);
|
||
raw_spin_unlock(&rcu_state.barrier_lock);
|
||
newcpu = !(rnp->expmaskinitnext & mask);
|
||
rnp->expmaskinitnext |= mask;
|
||
/* Allow lockless access for expedited grace periods. */
|
||
smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + newcpu); /* ^^^ */
|
||
ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus);
|
||
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
|
||
rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq);
|
||
rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags);
|
||
|
||
/* An incoming CPU should never be blocking a grace period. */
|
||
if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */
|
||
/* rcu_report_qs_rnp() *really* wants some flags to restore */
|
||
unsigned long flags;
|
||
|
||
local_irq_save(flags);
|
||
rcu_disable_urgency_upon_qs(rdp);
|
||
/* Report QS -after- changing ->qsmaskinitnext! */
|
||
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
||
} else {
|
||
raw_spin_unlock_rcu_node(rnp);
|
||
}
|
||
arch_spin_unlock(&rcu_state.ofl_lock);
|
||
smp_store_release(&rdp->beenonline, true);
|
||
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
|
||
}
|
||
|
||
/*
|
||
* The outgoing function has no further need of RCU, so remove it from
|
||
* the rcu_node tree's ->qsmaskinitnext bit masks.
|
||
*
|
||
* Note that this function is special in that it is invoked directly
|
||
* from the outgoing CPU rather than from the cpuhp_step mechanism.
|
||
* This is because this function must be invoked at a precise location.
|
||
*
|
||
* This mirrors the effect of rcutree_report_cpu_starting().
|
||
*/
|
||
void rcutree_report_cpu_dead(void)
|
||
{
|
||
unsigned long flags;
|
||
unsigned long mask;
|
||
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
||
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
|
||
|
||
/*
|
||
* IRQS must be disabled from now on and until the CPU dies, or an interrupt
|
||
* may introduce a new READ-side while it is actually off the QS masks.
|
||
*/
|
||
lockdep_assert_irqs_disabled();
|
||
// Do any dangling deferred wakeups.
|
||
do_nocb_deferred_wakeup(rdp);
|
||
|
||
rcu_preempt_deferred_qs(current);
|
||
|
||
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
|
||
mask = rdp->grpmask;
|
||
arch_spin_lock(&rcu_state.ofl_lock);
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
|
||
rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);
|
||
rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags);
|
||
if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */
|
||
/* Report quiescent state -before- changing ->qsmaskinitnext! */
|
||
rcu_disable_urgency_upon_qs(rdp);
|
||
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
}
|
||
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask);
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
arch_spin_unlock(&rcu_state.ofl_lock);
|
||
rdp->cpu_started = false;
|
||
}
|
||
|
||
#ifdef CONFIG_HOTPLUG_CPU
|
||
/*
|
||
* The outgoing CPU has just passed through the dying-idle state, and we
|
||
* are being invoked from the CPU that was IPIed to continue the offline
|
||
* operation. Migrate the outgoing CPU's callbacks to the current CPU.
|
||
*/
|
||
void rcutree_migrate_callbacks(int cpu)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_data *my_rdp;
|
||
struct rcu_node *my_rnp;
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
bool needwake;
|
||
|
||
if (rcu_rdp_is_offloaded(rdp) ||
|
||
rcu_segcblist_empty(&rdp->cblist))
|
||
return; /* No callbacks to migrate. */
|
||
|
||
raw_spin_lock_irqsave(&rcu_state.barrier_lock, flags);
|
||
WARN_ON_ONCE(rcu_rdp_cpu_online(rdp));
|
||
rcu_barrier_entrain(rdp);
|
||
my_rdp = this_cpu_ptr(&rcu_data);
|
||
my_rnp = my_rdp->mynode;
|
||
rcu_nocb_lock(my_rdp); /* irqs already disabled. */
|
||
WARN_ON_ONCE(!rcu_nocb_flush_bypass(my_rdp, NULL, jiffies, false));
|
||
raw_spin_lock_rcu_node(my_rnp); /* irqs already disabled. */
|
||
/* Leverage recent GPs and set GP for new callbacks. */
|
||
needwake = rcu_advance_cbs(my_rnp, rdp) ||
|
||
rcu_advance_cbs(my_rnp, my_rdp);
|
||
rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist);
|
||
raw_spin_unlock(&rcu_state.barrier_lock); /* irqs remain disabled. */
|
||
needwake = needwake || rcu_advance_cbs(my_rnp, my_rdp);
|
||
rcu_segcblist_disable(&rdp->cblist);
|
||
WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != !rcu_segcblist_n_cbs(&my_rdp->cblist));
|
||
check_cb_ovld_locked(my_rdp, my_rnp);
|
||
if (rcu_rdp_is_offloaded(my_rdp)) {
|
||
raw_spin_unlock_rcu_node(my_rnp); /* irqs remain disabled. */
|
||
__call_rcu_nocb_wake(my_rdp, true, flags);
|
||
} else {
|
||
rcu_nocb_unlock(my_rdp); /* irqs remain disabled. */
|
||
raw_spin_unlock_irqrestore_rcu_node(my_rnp, flags);
|
||
}
|
||
if (needwake)
|
||
rcu_gp_kthread_wake();
|
||
lockdep_assert_irqs_enabled();
|
||
WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 ||
|
||
!rcu_segcblist_empty(&rdp->cblist),
|
||
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n",
|
||
cpu, rcu_segcblist_n_cbs(&rdp->cblist),
|
||
rcu_segcblist_first_cb(&rdp->cblist));
|
||
}
|
||
|
||
/*
|
||
* The CPU has been completely removed, and some other CPU is reporting
|
||
* this fact from process context. Do the remainder of the cleanup.
|
||
* There can only be one CPU hotplug operation at a time, so no need for
|
||
* explicit locking.
|
||
*/
|
||
int rcutree_dead_cpu(unsigned int cpu)
|
||
{
|
||
WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1);
|
||
// Stop-machine done, so allow nohz_full to disable tick.
|
||
tick_dep_clear(TICK_DEP_BIT_RCU);
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Near the end of the offline process. Trace the fact that this CPU
|
||
* is going offline.
|
||
*/
|
||
int rcutree_dying_cpu(unsigned int cpu)
|
||
{
|
||
bool blkd;
|
||
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
struct rcu_node *rnp = rdp->mynode;
|
||
|
||
blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask);
|
||
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
|
||
blkd ? TPS("cpuofl-bgp") : TPS("cpuofl"));
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* Near the beginning of the process. The CPU is still very much alive
|
||
* with pretty much all services enabled.
|
||
*/
|
||
int rcutree_offline_cpu(unsigned int cpu)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_data *rdp;
|
||
struct rcu_node *rnp;
|
||
|
||
rdp = per_cpu_ptr(&rcu_data, cpu);
|
||
rnp = rdp->mynode;
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
rnp->ffmask &= ~rdp->grpmask;
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
|
||
rcutree_affinity_setting(cpu, cpu);
|
||
|
||
// nohz_full CPUs need the tick for stop-machine to work quickly
|
||
tick_dep_set(TICK_DEP_BIT_RCU);
|
||
return 0;
|
||
}
|
||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||
|
||
/*
|
||
* On non-huge systems, use expedited RCU grace periods to make suspend
|
||
* and hibernation run faster.
|
||
*/
|
||
static int rcu_pm_notify(struct notifier_block *self,
|
||
unsigned long action, void *hcpu)
|
||
{
|
||
switch (action) {
|
||
case PM_HIBERNATION_PREPARE:
|
||
case PM_SUSPEND_PREPARE:
|
||
rcu_async_hurry();
|
||
rcu_expedite_gp();
|
||
break;
|
||
case PM_POST_HIBERNATION:
|
||
case PM_POST_SUSPEND:
|
||
rcu_unexpedite_gp();
|
||
rcu_async_relax();
|
||
break;
|
||
default:
|
||
break;
|
||
}
|
||
return NOTIFY_OK;
|
||
}
|
||
|
||
#ifdef CONFIG_RCU_EXP_KTHREAD
|
||
struct kthread_worker *rcu_exp_gp_kworker;
|
||
struct kthread_worker *rcu_exp_par_gp_kworker;
|
||
|
||
static void __init rcu_start_exp_gp_kworkers(void)
|
||
{
|
||
const char *par_gp_kworker_name = "rcu_exp_par_gp_kthread_worker";
|
||
const char *gp_kworker_name = "rcu_exp_gp_kthread_worker";
|
||
struct sched_param param = { .sched_priority = kthread_prio };
|
||
|
||
rcu_exp_gp_kworker = kthread_create_worker(0, gp_kworker_name);
|
||
if (IS_ERR_OR_NULL(rcu_exp_gp_kworker)) {
|
||
pr_err("Failed to create %s!\n", gp_kworker_name);
|
||
return;
|
||
}
|
||
|
||
rcu_exp_par_gp_kworker = kthread_create_worker(0, par_gp_kworker_name);
|
||
if (IS_ERR_OR_NULL(rcu_exp_par_gp_kworker)) {
|
||
pr_err("Failed to create %s!\n", par_gp_kworker_name);
|
||
kthread_destroy_worker(rcu_exp_gp_kworker);
|
||
return;
|
||
}
|
||
|
||
sched_setscheduler_nocheck(rcu_exp_gp_kworker->task, SCHED_FIFO, ¶m);
|
||
sched_setscheduler_nocheck(rcu_exp_par_gp_kworker->task, SCHED_FIFO,
|
||
¶m);
|
||
}
|
||
|
||
static inline void rcu_alloc_par_gp_wq(void)
|
||
{
|
||
}
|
||
#else /* !CONFIG_RCU_EXP_KTHREAD */
|
||
struct workqueue_struct *rcu_par_gp_wq;
|
||
|
||
static void __init rcu_start_exp_gp_kworkers(void)
|
||
{
|
||
}
|
||
|
||
static inline void rcu_alloc_par_gp_wq(void)
|
||
{
|
||
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
|
||
WARN_ON(!rcu_par_gp_wq);
|
||
}
|
||
#endif /* CONFIG_RCU_EXP_KTHREAD */
|
||
|
||
/*
|
||
* Spawn the kthreads that handle RCU's grace periods.
|
||
*/
|
||
static int __init rcu_spawn_gp_kthread(void)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_node *rnp;
|
||
struct sched_param sp;
|
||
struct task_struct *t;
|
||
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
||
|
||
rcu_scheduler_fully_active = 1;
|
||
t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name);
|
||
if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__))
|
||
return 0;
|
||
if (kthread_prio) {
|
||
sp.sched_priority = kthread_prio;
|
||
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
|
||
}
|
||
rnp = rcu_get_root();
|
||
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
||
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
||
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
|
||
// Reset .gp_activity and .gp_req_activity before setting .gp_kthread.
|
||
smp_store_release(&rcu_state.gp_kthread, t); /* ^^^ */
|
||
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
||
wake_up_process(t);
|
||
/* This is a pre-SMP initcall, we expect a single CPU */
|
||
WARN_ON(num_online_cpus() > 1);
|
||
/*
|
||
* Those kthreads couldn't be created on rcu_init() -> rcutree_prepare_cpu()
|
||
* due to rcu_scheduler_fully_active.
|
||
*/
|
||
rcu_spawn_cpu_nocb_kthread(smp_processor_id());
|
||
rcu_spawn_one_boost_kthread(rdp->mynode);
|
||
rcu_spawn_core_kthreads();
|
||
/* Create kthread worker for expedited GPs */
|
||
rcu_start_exp_gp_kworkers();
|
||
return 0;
|
||
}
|
||
early_initcall(rcu_spawn_gp_kthread);
|
||
|
||
/*
|
||
* This function is invoked towards the end of the scheduler's
|
||
* initialization process. Before this is called, the idle task might
|
||
* contain synchronous grace-period primitives (during which time, this idle
|
||
* task is booting the system, and such primitives are no-ops). After this
|
||
* function is called, any synchronous grace-period primitives are run as
|
||
* expedited, with the requesting task driving the grace period forward.
|
||
* A later core_initcall() rcu_set_runtime_mode() will switch to full
|
||
* runtime RCU functionality.
|
||
*/
|
||
void rcu_scheduler_starting(void)
|
||
{
|
||
unsigned long flags;
|
||
struct rcu_node *rnp;
|
||
|
||
WARN_ON(num_online_cpus() != 1);
|
||
WARN_ON(nr_context_switches() > 0);
|
||
rcu_test_sync_prims();
|
||
|
||
// Fix up the ->gp_seq counters.
|
||
local_irq_save(flags);
|
||
rcu_for_each_node_breadth_first(rnp)
|
||
rnp->gp_seq_needed = rnp->gp_seq = rcu_state.gp_seq;
|
||
local_irq_restore(flags);
|
||
|
||
// Switch out of early boot mode.
|
||
rcu_scheduler_active = RCU_SCHEDULER_INIT;
|
||
rcu_test_sync_prims();
|
||
}
|
||
|
||
/*
|
||
* Helper function for rcu_init() that initializes the rcu_state structure.
|
||
*/
|
||
static void __init rcu_init_one(void)
|
||
{
|
||
static const char * const buf[] = RCU_NODE_NAME_INIT;
|
||
static const char * const fqs[] = RCU_FQS_NAME_INIT;
|
||
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
|
||
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
|
||
|
||
int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */
|
||
int cpustride = 1;
|
||
int i;
|
||
int j;
|
||
struct rcu_node *rnp;
|
||
|
||
BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
|
||
|
||
/* Silence gcc 4.8 false positive about array index out of range. */
|
||
if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS)
|
||
panic("rcu_init_one: rcu_num_lvls out of range");
|
||
|
||
/* Initialize the level-tracking arrays. */
|
||
|
||
for (i = 1; i < rcu_num_lvls; i++)
|
||
rcu_state.level[i] =
|
||
rcu_state.level[i - 1] + num_rcu_lvl[i - 1];
|
||
rcu_init_levelspread(levelspread, num_rcu_lvl);
|
||
|
||
/* Initialize the elements themselves, starting from the leaves. */
|
||
|
||
for (i = rcu_num_lvls - 1; i >= 0; i--) {
|
||
cpustride *= levelspread[i];
|
||
rnp = rcu_state.level[i];
|
||
for (j = 0; j < num_rcu_lvl[i]; j++, rnp++) {
|
||
raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock));
|
||
lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock),
|
||
&rcu_node_class[i], buf[i]);
|
||
raw_spin_lock_init(&rnp->fqslock);
|
||
lockdep_set_class_and_name(&rnp->fqslock,
|
||
&rcu_fqs_class[i], fqs[i]);
|
||
rnp->gp_seq = rcu_state.gp_seq;
|
||
rnp->gp_seq_needed = rcu_state.gp_seq;
|
||
rnp->completedqs = rcu_state.gp_seq;
|
||
rnp->qsmask = 0;
|
||
rnp->qsmaskinit = 0;
|
||
rnp->grplo = j * cpustride;
|
||
rnp->grphi = (j + 1) * cpustride - 1;
|
||
if (rnp->grphi >= nr_cpu_ids)
|
||
rnp->grphi = nr_cpu_ids - 1;
|
||
if (i == 0) {
|
||
rnp->grpnum = 0;
|
||
rnp->grpmask = 0;
|
||
rnp->parent = NULL;
|
||
} else {
|
||
rnp->grpnum = j % levelspread[i - 1];
|
||
rnp->grpmask = BIT(rnp->grpnum);
|
||
rnp->parent = rcu_state.level[i - 1] +
|
||
j / levelspread[i - 1];
|
||
}
|
||
rnp->level = i;
|
||
INIT_LIST_HEAD(&rnp->blkd_tasks);
|
||
rcu_init_one_nocb(rnp);
|
||
init_waitqueue_head(&rnp->exp_wq[0]);
|
||
init_waitqueue_head(&rnp->exp_wq[1]);
|
||
init_waitqueue_head(&rnp->exp_wq[2]);
|
||
init_waitqueue_head(&rnp->exp_wq[3]);
|
||
spin_lock_init(&rnp->exp_lock);
|
||
mutex_init(&rnp->boost_kthread_mutex);
|
||
raw_spin_lock_init(&rnp->exp_poll_lock);
|
||
rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED;
|
||
INIT_WORK(&rnp->exp_poll_wq, sync_rcu_do_polled_gp);
|
||
}
|
||
}
|
||
|
||
init_swait_queue_head(&rcu_state.gp_wq);
|
||
init_swait_queue_head(&rcu_state.expedited_wq);
|
||
rnp = rcu_first_leaf_node();
|
||
for_each_possible_cpu(i) {
|
||
while (i > rnp->grphi)
|
||
rnp++;
|
||
per_cpu_ptr(&rcu_data, i)->mynode = rnp;
|
||
rcu_boot_init_percpu_data(i);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Force priority from the kernel command-line into range.
|
||
*/
|
||
static void __init sanitize_kthread_prio(void)
|
||
{
|
||
int kthread_prio_in = kthread_prio;
|
||
|
||
if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2
|
||
&& IS_BUILTIN(CONFIG_RCU_TORTURE_TEST))
|
||
kthread_prio = 2;
|
||
else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
|
||
kthread_prio = 1;
|
||
else if (kthread_prio < 0)
|
||
kthread_prio = 0;
|
||
else if (kthread_prio > 99)
|
||
kthread_prio = 99;
|
||
|
||
if (kthread_prio != kthread_prio_in)
|
||
pr_alert("%s: Limited prio to %d from %d\n",
|
||
__func__, kthread_prio, kthread_prio_in);
|
||
}
|
||
|
||
/*
|
||
* Compute the rcu_node tree geometry from kernel parameters. This cannot
|
||
* replace the definitions in tree.h because those are needed to size
|
||
* the ->node array in the rcu_state structure.
|
||
*/
|
||
void rcu_init_geometry(void)
|
||
{
|
||
ulong d;
|
||
int i;
|
||
static unsigned long old_nr_cpu_ids;
|
||
int rcu_capacity[RCU_NUM_LVLS];
|
||
static bool initialized;
|
||
|
||
if (initialized) {
|
||
/*
|
||
* Warn if setup_nr_cpu_ids() had not yet been invoked,
|
||
* unless nr_cpus_ids == NR_CPUS, in which case who cares?
|
||
*/
|
||
WARN_ON_ONCE(old_nr_cpu_ids != nr_cpu_ids);
|
||
return;
|
||
}
|
||
|
||
old_nr_cpu_ids = nr_cpu_ids;
|
||
initialized = true;
|
||
|
||
/*
|
||
* Initialize any unspecified boot parameters.
|
||
* The default values of jiffies_till_first_fqs and
|
||
* jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
|
||
* value, which is a function of HZ, then adding one for each
|
||
* RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
|
||
*/
|
||
d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
|
||
if (jiffies_till_first_fqs == ULONG_MAX)
|
||
jiffies_till_first_fqs = d;
|
||
if (jiffies_till_next_fqs == ULONG_MAX)
|
||
jiffies_till_next_fqs = d;
|
||
adjust_jiffies_till_sched_qs();
|
||
|
||
/* If the compile-time values are accurate, just leave. */
|
||
if (rcu_fanout_leaf == RCU_FANOUT_LEAF &&
|
||
nr_cpu_ids == NR_CPUS)
|
||
return;
|
||
pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
|
||
rcu_fanout_leaf, nr_cpu_ids);
|
||
|
||
/*
|
||
* The boot-time rcu_fanout_leaf parameter must be at least two
|
||
* and cannot exceed the number of bits in the rcu_node masks.
|
||
* Complain and fall back to the compile-time values if this
|
||
* limit is exceeded.
|
||
*/
|
||
if (rcu_fanout_leaf < 2 ||
|
||
rcu_fanout_leaf > sizeof(unsigned long) * 8) {
|
||
rcu_fanout_leaf = RCU_FANOUT_LEAF;
|
||
WARN_ON(1);
|
||
return;
|
||
}
|
||
|
||
/*
|
||
* Compute number of nodes that can be handled an rcu_node tree
|
||
* with the given number of levels.
|
||
*/
|
||
rcu_capacity[0] = rcu_fanout_leaf;
|
||
for (i = 1; i < RCU_NUM_LVLS; i++)
|
||
rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
|
||
|
||
/*
|
||
* The tree must be able to accommodate the configured number of CPUs.
|
||
* If this limit is exceeded, fall back to the compile-time values.
|
||
*/
|
||
if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) {
|
||
rcu_fanout_leaf = RCU_FANOUT_LEAF;
|
||
WARN_ON(1);
|
||
return;
|
||
}
|
||
|
||
/* Calculate the number of levels in the tree. */
|
||
for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) {
|
||
}
|
||
rcu_num_lvls = i + 1;
|
||
|
||
/* Calculate the number of rcu_nodes at each level of the tree. */
|
||
for (i = 0; i < rcu_num_lvls; i++) {
|
||
int cap = rcu_capacity[(rcu_num_lvls - 1) - i];
|
||
num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap);
|
||
}
|
||
|
||
/* Calculate the total number of rcu_node structures. */
|
||
rcu_num_nodes = 0;
|
||
for (i = 0; i < rcu_num_lvls; i++)
|
||
rcu_num_nodes += num_rcu_lvl[i];
|
||
}
|
||
|
||
/*
|
||
* Dump out the structure of the rcu_node combining tree associated
|
||
* with the rcu_state structure.
|
||
*/
|
||
static void __init rcu_dump_rcu_node_tree(void)
|
||
{
|
||
int level = 0;
|
||
struct rcu_node *rnp;
|
||
|
||
pr_info("rcu_node tree layout dump\n");
|
||
pr_info(" ");
|
||
rcu_for_each_node_breadth_first(rnp) {
|
||
if (rnp->level != level) {
|
||
pr_cont("\n");
|
||
pr_info(" ");
|
||
level = rnp->level;
|
||
}
|
||
pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum);
|
||
}
|
||
pr_cont("\n");
|
||
}
|
||
|
||
struct workqueue_struct *rcu_gp_wq;
|
||
|
||
static void __init kfree_rcu_batch_init(void)
|
||
{
|
||
int cpu;
|
||
int i, j;
|
||
struct shrinker *kfree_rcu_shrinker;
|
||
|
||
/* Clamp it to [0:100] seconds interval. */
|
||
if (rcu_delay_page_cache_fill_msec < 0 ||
|
||
rcu_delay_page_cache_fill_msec > 100 * MSEC_PER_SEC) {
|
||
|
||
rcu_delay_page_cache_fill_msec =
|
||
clamp(rcu_delay_page_cache_fill_msec, 0,
|
||
(int) (100 * MSEC_PER_SEC));
|
||
|
||
pr_info("Adjusting rcutree.rcu_delay_page_cache_fill_msec to %d ms.\n",
|
||
rcu_delay_page_cache_fill_msec);
|
||
}
|
||
|
||
for_each_possible_cpu(cpu) {
|
||
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
||
|
||
for (i = 0; i < KFREE_N_BATCHES; i++) {
|
||
INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
|
||
krcp->krw_arr[i].krcp = krcp;
|
||
|
||
for (j = 0; j < FREE_N_CHANNELS; j++)
|
||
INIT_LIST_HEAD(&krcp->krw_arr[i].bulk_head_free[j]);
|
||
}
|
||
|
||
for (i = 0; i < FREE_N_CHANNELS; i++)
|
||
INIT_LIST_HEAD(&krcp->bulk_head[i]);
|
||
|
||
INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
|
||
INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func);
|
||
krcp->initialized = true;
|
||
}
|
||
|
||
kfree_rcu_shrinker = shrinker_alloc(0, "rcu-kfree");
|
||
if (!kfree_rcu_shrinker) {
|
||
pr_err("Failed to allocate kfree_rcu() shrinker!\n");
|
||
return;
|
||
}
|
||
|
||
kfree_rcu_shrinker->count_objects = kfree_rcu_shrink_count;
|
||
kfree_rcu_shrinker->scan_objects = kfree_rcu_shrink_scan;
|
||
|
||
shrinker_register(kfree_rcu_shrinker);
|
||
}
|
||
|
||
void __init rcu_init(void)
|
||
{
|
||
int cpu = smp_processor_id();
|
||
|
||
rcu_early_boot_tests();
|
||
|
||
kfree_rcu_batch_init();
|
||
rcu_bootup_announce();
|
||
sanitize_kthread_prio();
|
||
rcu_init_geometry();
|
||
rcu_init_one();
|
||
if (dump_tree)
|
||
rcu_dump_rcu_node_tree();
|
||
if (use_softirq)
|
||
open_softirq(RCU_SOFTIRQ, rcu_core_si);
|
||
|
||
/*
|
||
* We don't need protection against CPU-hotplug here because
|
||
* this is called early in boot, before either interrupts
|
||
* or the scheduler are operational.
|
||
*/
|
||
pm_notifier(rcu_pm_notify, 0);
|
||
WARN_ON(num_online_cpus() > 1); // Only one CPU this early in boot.
|
||
rcutree_prepare_cpu(cpu);
|
||
rcutree_report_cpu_starting(cpu);
|
||
rcutree_online_cpu(cpu);
|
||
|
||
/* Create workqueue for Tree SRCU and for expedited GPs. */
|
||
rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);
|
||
WARN_ON(!rcu_gp_wq);
|
||
rcu_alloc_par_gp_wq();
|
||
|
||
/* Fill in default value for rcutree.qovld boot parameter. */
|
||
/* -After- the rcu_node ->lock fields are initialized! */
|
||
if (qovld < 0)
|
||
qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark;
|
||
else
|
||
qovld_calc = qovld;
|
||
|
||
// Kick-start in case any polled grace periods started early.
|
||
(void)start_poll_synchronize_rcu_expedited();
|
||
|
||
rcu_test_sync_prims();
|
||
}
|
||
|
||
#include "tree_stall.h"
|
||
#include "tree_exp.h"
|
||
#include "tree_nocb.h"
|
||
#include "tree_plugin.h"
|