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rcu/context-tracking: Remove unused and/or unecessary middle functions

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Some eqs functions are now only used internally by context tracking, so
their public declarations can be removed.

Also middle functions such as rcu_user_*() and rcu_idle_*()
which now directly call to rcu_eqs_enter() and rcu_eqs_exit() can be
wiped out as well.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
This commit is contained in:
Frederic Weisbecker 2022-06-08 16:40:34 +02:00 committed by Paul E. McKenney
parent 1721145527
commit c33ef43a35
6 changed files with 28 additions and 92 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/RCU/stallwarn.rst
View File

@ -97,7 +97,7 @@ warnings:
which will include additional debugging information.
- A low-level kernel issue that either fails to invoke one of the
variants of rcu_user_enter(), rcu_user_exit(), ct_idle_enter(),
variants of rcu_eqs_enter(true), rcu_eqs_exit(true), ct_idle_enter(),
ct_idle_exit(), ct_irq_enter(), or ct_irq_exit() on the one
hand, or that invokes one of them too many times on the other.
Historically, the most frequent issue has been an omission

8
include/linux/hardirq.h
View File

@ -92,14 +92,6 @@ void irq_exit_rcu(void);
#define arch_nmi_exit() do { } while (0)
#endif
#ifdef CONFIG_TINY_RCU
static inline void rcu_nmi_enter(void) { }
static inline void rcu_nmi_exit(void) { }
#else
extern void rcu_nmi_enter(void);
extern void rcu_nmi_exit(void);
#endif
/*
* NMI vs Tracing
* --------------

8
include/linux/rcupdate.h
View File

@ -104,14 +104,6 @@ static inline void rcu_sysrq_start(void) { }
static inline void rcu_sysrq_end(void) { }
#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
#ifdef CONFIG_NO_HZ_FULL
void rcu_user_enter(void);
void rcu_user_exit(void);
#else
static inline void rcu_user_enter(void) { }
static inline void rcu_user_exit(void) { }
#endif /* CONFIG_NO_HZ_FULL */
#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
void rcu_irq_work_resched(void);
#else

2
include/linux/rcutiny.h
View File

@ -76,8 +76,6 @@ static inline int rcu_needs_cpu(void)
static inline void rcu_virt_note_context_switch(int cpu) { }
static inline void rcu_cpu_stall_reset(void) { }
static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
static inline void rcu_idle_enter(void) { }
static inline void rcu_idle_exit(void) { }
static inline void rcu_irq_exit_check_preempt(void) { }
#define rcu_is_idle_cpu(cpu) \
(is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq())

2
include/linux/rcutree.h
View File

@ -45,8 +45,6 @@ unsigned long start_poll_synchronize_rcu(void);
bool poll_state_synchronize_rcu(unsigned long oldstate);
void cond_synchronize_rcu(unsigned long oldstate);
void rcu_idle_enter(void);
void rcu_idle_exit(void);
bool rcu_is_idle_cpu(int cpu);
#ifdef CONFIG_PROVE_RCU

98
kernel/context_tracking.c
View File

@ -189,17 +189,17 @@ static void noinstr rcu_eqs_exit(bool user)
}
/**
* rcu_nmi_exit - inform RCU of exit from NMI context
* ct_nmi_exit - inform RCU of exit from NMI context
*
* If we are returning from the outermost NMI handler that interrupted an
* RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
* to let the RCU grace-period handling know that the CPU is back to
* being RCU-idle.
*
* If you add or remove a call to rcu_nmi_exit(), be sure to test
* If you add or remove a call to ct_nmi_exit(), be sure to test
* with CONFIG_RCU_EQS_DEBUG=y.
*/
void noinstr rcu_nmi_exit(void)
void noinstr ct_nmi_exit(void)
{
struct context_tracking *ct = this_cpu_ptr(&context_tracking);
@ -242,7 +242,7 @@ void noinstr rcu_nmi_exit(void)
}
/**
* rcu_nmi_enter - inform RCU of entry to NMI context
* ct_nmi_enter - inform RCU of entry to NMI context
*
* If the CPU was idle from RCU's viewpoint, update ct->dynticks and
* ct->dynticks_nmi_nesting to let the RCU grace-period handling know
@ -250,10 +250,10 @@ void noinstr rcu_nmi_exit(void)
* long as the nesting level does not overflow an int. (You will probably
* run out of stack space first.)
*
* If you add or remove a call to rcu_nmi_enter(), be sure to test
* If you add or remove a call to ct_nmi_enter(), be sure to test
* with CONFIG_RCU_EQS_DEBUG=y.
*/
void noinstr rcu_nmi_enter(void)
void noinstr ct_nmi_enter(void)
{
long incby = 2;
struct context_tracking *ct = this_cpu_ptr(&context_tracking);
@ -302,32 +302,33 @@ void noinstr rcu_nmi_enter(void)
}
/**
* rcu_idle_enter - inform RCU that current CPU is entering idle
* ct_idle_enter - inform RCU that current CPU is entering idle
*
* Enter idle mode, in other words, -leave- the mode in which RCU
* read-side critical sections can occur. (Though RCU read-side
* critical sections can occur in irq handlers in idle, a possibility
* handled by irq_enter() and irq_exit().)
*
* If you add or remove a call to rcu_idle_enter(), be sure to test with
* If you add or remove a call to ct_idle_enter(), be sure to test with
* CONFIG_RCU_EQS_DEBUG=y.
*/
void noinstr rcu_idle_enter(void)
void noinstr ct_idle_enter(void)
{
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
rcu_eqs_enter(false);
}
EXPORT_SYMBOL_GPL(ct_idle_enter);
/**
* rcu_idle_exit - inform RCU that current CPU is leaving idle
* ct_idle_exit - inform RCU that current CPU is leaving idle
*
* Exit idle mode, in other words, -enter- the mode in which RCU
* read-side critical sections can occur.
*
* If you add or remove a call to rcu_idle_exit(), be sure to test with
* If you add or remove a call to ct_idle_exit(), be sure to test with
* CONFIG_RCU_EQS_DEBUG=y.
*/
void noinstr rcu_idle_exit(void)
void noinstr ct_idle_exit(void)
{
unsigned long flags;
@ -335,18 +336,6 @@ void noinstr rcu_idle_exit(void)
rcu_eqs_exit(false);
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_idle_exit);
noinstr void ct_idle_enter(void)
{
rcu_idle_enter();
}
EXPORT_SYMBOL_GPL(ct_idle_enter);
void ct_idle_exit(void)
{
rcu_idle_exit();
}
EXPORT_SYMBOL_GPL(ct_idle_exit);
/**
@ -431,50 +420,11 @@ void ct_irq_exit_irqson(void)
ct_irq_exit();
local_irq_restore(flags);
}
noinstr void ct_nmi_enter(void)
{
rcu_nmi_enter();
}
noinstr void ct_nmi_exit(void)
{
rcu_nmi_exit();
}
#else
static __always_inline void rcu_eqs_enter(bool user) { }
static __always_inline void rcu_eqs_exit(bool user) { }
#endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
#ifdef CONFIG_NO_HZ_FULL
/**
* rcu_user_enter - inform RCU that we are resuming userspace.
*
* Enter RCU idle mode right before resuming userspace. No use of RCU
* is permitted between this call and rcu_user_exit(). This way the
* CPU doesn't need to maintain the tick for RCU maintenance purposes
* when the CPU runs in userspace.
*
* If you add or remove a call to rcu_user_enter(), be sure to test with
* CONFIG_RCU_EQS_DEBUG=y.
*/
noinstr void rcu_user_enter(void)
{
rcu_eqs_enter(true);
}
/**
* rcu_user_exit - inform RCU that we are exiting userspace.
*
* Exit RCU idle mode while entering the kernel because it can
* run a RCU read side critical section anytime.
*
* If you add or remove a call to rcu_user_exit(), be sure to test with
* CONFIG_RCU_EQS_DEBUG=y.
*/
void noinstr rcu_user_exit(void)
{
rcu_eqs_exit(true);
}
#endif /* #ifdef CONFIG_NO_HZ_FULL */
#ifdef CONFIG_CONTEXT_TRACKING_USER
#define CREATE_TRACE_POINTS
@ -542,7 +492,13 @@ void noinstr __ct_user_enter(enum ctx_state state)
* that will fire and reschedule once we resume in user/guest mode.
*/
rcu_irq_work_resched();
rcu_user_enter();
/*
* Enter RCU idle mode right before resuming userspace. No use of RCU
* is permitted between this call and rcu_eqs_exit(). This way the
* CPU doesn't need to maintain the tick for RCU maintenance purposes
* when the CPU runs in userspace.
*/
rcu_eqs_enter(true);
}
/*
* Even if context tracking is disabled on this CPU, because it's outside
@ -579,7 +535,7 @@ void ct_user_enter(enum ctx_state state)
/*
* Some contexts may involve an exception occuring in an irq,
* leading to that nesting:
* ct_irq_enter() rcu_user_exit() rcu_user_exit() ct_irq_exit()
* ct_irq_enter() rcu_eqs_exit(true) rcu_eqs_enter(true) ct_irq_exit()
* This would mess up the dyntick_nesting count though. And rcu_irq_*()
* helpers are enough to protect RCU uses inside the exception. So
* just return immediately if we detect we are in an IRQ.
@ -631,10 +587,10 @@ void noinstr __ct_user_exit(enum ctx_state state)
if (__this_cpu_read(context_tracking.state) == state) {
if (__this_cpu_read(context_tracking.active)) {
/*
* We are going to run code that may use RCU. Inform
* RCU core about that (ie: we may need the tick again).
* Exit RCU idle mode while entering the kernel because it can
* run a RCU read side critical section anytime.
*/
rcu_user_exit();
rcu_eqs_exit(true);
if (state == CONTEXT_USER) {
instrumentation_begin();
vtime_user_exit(current);