2005-04-17 02:20:36 +04:00
/* CPU control.
* ( C ) 2001 , 2002 , 2003 , 2004 Rusty Russell
*
* This code is licenced under the GPL .
*/
# include <linux/proc_fs.h>
# include <linux/smp.h>
# include <linux/init.h>
# include <linux/notifier.h>
# include <linux/sched.h>
# include <linux/unistd.h>
# include <linux/cpu.h>
cpu: introduce clear_tasks_mm_cpumask() helper
Many architectures clear tasks' mm_cpumask like this:
read_lock(&tasklist_lock);
for_each_process(p) {
if (p->mm)
cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
}
read_unlock(&tasklist_lock);
Depending on the context, the code above may have several problems,
such as:
1. Working with task->mm w/o getting mm or grabing the task lock is
dangerous as ->mm might disappear (exit_mm() assigns NULL under
task_lock(), so tasklist lock is not enough).
2. Checking for process->mm is not enough because process' main
thread may exit or detach its mm via use_mm(), but other threads
may still have a valid mm.
This patch implements a small helper function that does things
correctly, i.e.:
1. We take the task's lock while whe handle its mm (we can't use
get_task_mm()/mmput() pair as mmput() might sleep);
2. To catch exited main thread case, we use find_lock_task_mm(),
which walks up all threads and returns an appropriate task
(with task lock held).
Also, Per Peter Zijlstra's idea, now we don't grab tasklist_lock in
the new helper, instead we take the rcu read lock. We can do this
because the function is called after the cpu is taken down and marked
offline, so no new tasks will get this cpu set in their mm mask.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-01 03:26:22 +04:00
# include <linux/oom.h>
# include <linux/rcupdate.h>
2011-05-23 22:51:41 +04:00
# include <linux/export.h>
2012-06-01 03:26:26 +04:00
# include <linux/bug.h>
2005-04-17 02:20:36 +04:00
# include <linux/kthread.h>
# include <linux/stop_machine.h>
2006-06-26 11:24:32 +04:00
# include <linux/mutex.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 11:04:11 +03:00
# include <linux/gfp.h>
2011-11-03 03:59:25 +04:00
# include <linux/suspend.h>
2014-03-11 00:34:03 +04:00
# include <linux/lockdep.h>
2015-03-30 12:29:19 +03:00
# include <linux/tick.h>
2015-07-05 20:12:30 +03:00
# include <linux/irq.h>
2016-02-26 21:43:38 +03:00
# include <linux/smpboot.h>
2016-02-26 21:43:28 +03:00
2014-06-06 16:40:17 +04:00
# include <trace/events/power.h>
2016-02-26 21:43:28 +03:00
# define CREATE_TRACE_POINTS
# include <trace/events/cpuhp.h>
2005-04-17 02:20:36 +04:00
2012-04-20 17:05:44 +04:00
# include "smpboot.h"
2016-02-26 21:43:28 +03:00
/**
* cpuhp_cpu_state - Per cpu hotplug state storage
* @ state : The current cpu state
* @ target : The target state
2016-02-26 21:43:38 +03:00
* @ thread : Pointer to the hotplug thread
* @ should_run : Thread should execute
* @ cb_stat : The state for a single callback ( install / uninstall )
* @ cb : Single callback function ( install / uninstall )
* @ result : Result of the operation
* @ done : Signal completion to the issuer of the task
2016-02-26 21:43:28 +03:00
*/
struct cpuhp_cpu_state {
enum cpuhp_state state ;
enum cpuhp_state target ;
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# ifdef CONFIG_SMP
struct task_struct * thread ;
bool should_run ;
enum cpuhp_state cb_state ;
int ( * cb ) ( unsigned int cpu ) ;
int result ;
struct completion done ;
# endif
2016-02-26 21:43:28 +03:00
} ;
static DEFINE_PER_CPU ( struct cpuhp_cpu_state , cpuhp_state ) ;
/**
* cpuhp_step - Hotplug state machine step
* @ name : Name of the step
* @ startup : Startup function of the step
* @ teardown : Teardown function of the step
* @ skip_onerr : Do not invoke the functions on error rollback
* Will go away once the notifiers are gone
2016-02-26 21:43:32 +03:00
* @ cant_stop : Bringup / teardown can ' t be stopped at this step
2016-02-26 21:43:28 +03:00
*/
struct cpuhp_step {
const char * name ;
int ( * startup ) ( unsigned int cpu ) ;
int ( * teardown ) ( unsigned int cpu ) ;
bool skip_onerr ;
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bool cant_stop ;
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} ;
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static DEFINE_MUTEX ( cpuhp_state_mutex ) ;
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static struct cpuhp_step cpuhp_bp_states [ ] ;
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static struct cpuhp_step cpuhp_ap_states [ ] ;
2016-02-26 21:43:28 +03:00
/**
* cpuhp_invoke_callback _ Invoke the callbacks for a given state
* @ cpu : The cpu for which the callback should be invoked
* @ step : The step in the state machine
* @ cb : The callback function to invoke
*
* Called from cpu hotplug and from the state register machinery
*/
static int cpuhp_invoke_callback ( unsigned int cpu , enum cpuhp_state step ,
int ( * cb ) ( unsigned int ) )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
int ret = 0 ;
if ( cb ) {
trace_cpuhp_enter ( cpu , st - > target , step , cb ) ;
ret = cb ( cpu ) ;
trace_cpuhp_exit ( cpu , st - > state , step , ret ) ;
}
return ret ;
}
2008-12-13 13:49:41 +03:00
# ifdef CONFIG_SMP
2008-12-30 01:35:14 +03:00
/* Serializes the updates to cpu_online_mask, cpu_present_mask */
2006-07-23 23:12:16 +04:00
static DEFINE_MUTEX ( cpu_add_remove_lock ) ;
2016-02-26 21:43:23 +03:00
bool cpuhp_tasks_frozen ;
EXPORT_SYMBOL_GPL ( cpuhp_tasks_frozen ) ;
2005-04-17 02:20:36 +04:00
2010-05-27 01:43:36 +04:00
/*
CPU hotplug: Provide lockless versions of callback registration functions
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 00:34:14 +04:00
* The following two APIs ( cpu_maps_update_begin / done ) must be used when
* attempting to serialize the updates to cpu_online_mask & cpu_present_mask .
* The APIs cpu_notifier_register_begin / done ( ) must be used to protect CPU
* hotplug callback ( un ) registration performed using __register_cpu_notifier ( )
* or __unregister_cpu_notifier ( ) .
2010-05-27 01:43:36 +04:00
*/
void cpu_maps_update_begin ( void )
{
mutex_lock ( & cpu_add_remove_lock ) ;
}
CPU hotplug: Provide lockless versions of callback registration functions
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 00:34:14 +04:00
EXPORT_SYMBOL ( cpu_notifier_register_begin ) ;
2010-05-27 01:43:36 +04:00
void cpu_maps_update_done ( void )
{
mutex_unlock ( & cpu_add_remove_lock ) ;
}
CPU hotplug: Provide lockless versions of callback registration functions
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 00:34:14 +04:00
EXPORT_SYMBOL ( cpu_notifier_register_done ) ;
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2010-06-01 15:15:11 +04:00
static RAW_NOTIFIER_HEAD ( cpu_chain ) ;
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/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
* Should always be manipulated under cpu_add_remove_lock
*/
static int cpu_hotplug_disabled ;
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# ifdef CONFIG_HOTPLUG_CPU
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static struct {
struct task_struct * active_writer ;
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/* wait queue to wake up the active_writer */
wait_queue_head_t wq ;
/* verifies that no writer will get active while readers are active */
struct mutex lock ;
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/*
* Also blocks the new readers during
* an ongoing cpu hotplug operation .
*/
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atomic_t refcount ;
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# ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map ;
# endif
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} cpu_hotplug = {
. active_writer = NULL ,
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. wq = __WAIT_QUEUE_HEAD_INITIALIZER ( cpu_hotplug . wq ) ,
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. lock = __MUTEX_INITIALIZER ( cpu_hotplug . lock ) ,
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# ifdef CONFIG_DEBUG_LOCK_ALLOC
. dep_map = { . name = " cpu_hotplug.lock " } ,
# endif
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} ;
2008-01-25 23:08:01 +03:00
2014-03-11 00:34:03 +04:00
/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
# define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
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# define cpuhp_lock_acquire_tryread() \
lock_map_acquire_tryread ( & cpu_hotplug . dep_map )
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# define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
# define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
2014-10-23 01:51:49 +04:00
2008-01-25 23:08:02 +03:00
void get_online_cpus ( void )
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{
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might_sleep ( ) ;
if ( cpu_hotplug . active_writer = = current )
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return ;
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cpuhp_lock_acquire_read ( ) ;
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mutex_lock ( & cpu_hotplug . lock ) ;
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atomic_inc ( & cpu_hotplug . refcount ) ;
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mutex_unlock ( & cpu_hotplug . lock ) ;
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}
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EXPORT_SYMBOL_GPL ( get_online_cpus ) ;
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2008-01-25 23:08:02 +03:00
void put_online_cpus ( void )
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{
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int refcount ;
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if ( cpu_hotplug . active_writer = = current )
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return ;
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2014-12-12 12:11:44 +03:00
refcount = atomic_dec_return ( & cpu_hotplug . refcount ) ;
if ( WARN_ON ( refcount < 0 ) ) /* try to fix things up */
atomic_inc ( & cpu_hotplug . refcount ) ;
if ( refcount < = 0 & & waitqueue_active ( & cpu_hotplug . wq ) )
wake_up ( & cpu_hotplug . wq ) ;
2012-10-09 03:28:20 +04:00
2014-03-11 00:34:03 +04:00
cpuhp_lock_release ( ) ;
2008-01-25 23:08:01 +03:00
2005-11-29 00:43:46 +03:00
}
2008-01-25 23:08:02 +03:00
EXPORT_SYMBOL_GPL ( put_online_cpus ) ;
2005-11-29 00:43:46 +03:00
2008-01-25 23:08:01 +03:00
/*
* This ensures that the hotplug operation can begin only when the
* refcount goes to zero .
*
* Note that during a cpu - hotplug operation , the new readers , if any ,
* will be blocked by the cpu_hotplug . lock
*
2008-04-29 12:00:29 +04:00
* Since cpu_hotplug_begin ( ) is always called after invoking
* cpu_maps_update_begin ( ) , we can be sure that only one writer is active .
2008-01-25 23:08:01 +03:00
*
* Note that theoretically , there is a possibility of a livelock :
* - Refcount goes to zero , last reader wakes up the sleeping
* writer .
* - Last reader unlocks the cpu_hotplug . lock .
* - A new reader arrives at this moment , bumps up the refcount .
* - The writer acquires the cpu_hotplug . lock finds the refcount
* non zero and goes to sleep again .
*
* However , this is very difficult to achieve in practice since
2008-01-25 23:08:02 +03:00
* get_online_cpus ( ) not an api which is called all that often .
2008-01-25 23:08:01 +03:00
*
*/
ACPI / processor: Acquire writer lock to update CPU maps
CPU system maps are protected with reader/writer locks. The reader
lock, get_online_cpus(), assures that the maps are not updated while
holding the lock. The writer lock, cpu_hotplug_begin(), is used to
udpate the cpu maps along with cpu_maps_update_begin().
However, the ACPI processor handler updates the cpu maps without
holding the the writer lock.
acpi_map_lsapic() is called from acpi_processor_hotadd_init() to
update cpu_possible_mask and cpu_present_mask. acpi_unmap_lsapic()
is called from acpi_processor_remove() to update cpu_possible_mask.
Currently, they are either unprotected or protected with the reader
lock, which is not correct.
For example, the get_online_cpus() below is supposed to assure that
cpu_possible_mask is not changed while the code is iterating with
for_each_possible_cpu().
get_online_cpus();
for_each_possible_cpu(cpu) {
:
}
put_online_cpus();
However, this lock has no protection with CPU hotplug since the ACPI
processor handler does not use the writer lock when it updates
cpu_possible_mask. The reader lock does not serialize within the
readers.
This patch protects them with the writer lock with cpu_hotplug_begin()
along with cpu_maps_update_begin(), which must be held before calling
cpu_hotplug_begin(). It also protects arch_register_cpu() /
arch_unregister_cpu(), which creates / deletes a sysfs cpu device
interface. For this purpose it changes cpu_hotplug_begin() and
cpu_hotplug_done() to global and exports them in cpu.h.
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2013-08-12 19:45:53 +04:00
void cpu_hotplug_begin ( void )
2008-01-25 23:08:01 +03:00
{
2014-12-12 12:11:44 +03:00
DEFINE_WAIT ( wait ) ;
2008-04-29 12:00:29 +04:00
2014-12-12 12:11:44 +03:00
cpu_hotplug . active_writer = current ;
2014-03-11 00:34:03 +04:00
cpuhp_lock_acquire ( ) ;
2014-12-12 12:11:44 +03:00
2008-04-29 12:00:29 +04:00
for ( ; ; ) {
mutex_lock ( & cpu_hotplug . lock ) ;
2014-12-12 12:11:44 +03:00
prepare_to_wait ( & cpu_hotplug . wq , & wait , TASK_UNINTERRUPTIBLE ) ;
if ( likely ( ! atomic_read ( & cpu_hotplug . refcount ) ) )
break ;
2008-01-25 23:08:01 +03:00
mutex_unlock ( & cpu_hotplug . lock ) ;
schedule ( ) ;
}
2014-12-12 12:11:44 +03:00
finish_wait ( & cpu_hotplug . wq , & wait ) ;
2008-01-25 23:08:01 +03:00
}
ACPI / processor: Acquire writer lock to update CPU maps
CPU system maps are protected with reader/writer locks. The reader
lock, get_online_cpus(), assures that the maps are not updated while
holding the lock. The writer lock, cpu_hotplug_begin(), is used to
udpate the cpu maps along with cpu_maps_update_begin().
However, the ACPI processor handler updates the cpu maps without
holding the the writer lock.
acpi_map_lsapic() is called from acpi_processor_hotadd_init() to
update cpu_possible_mask and cpu_present_mask. acpi_unmap_lsapic()
is called from acpi_processor_remove() to update cpu_possible_mask.
Currently, they are either unprotected or protected with the reader
lock, which is not correct.
For example, the get_online_cpus() below is supposed to assure that
cpu_possible_mask is not changed while the code is iterating with
for_each_possible_cpu().
get_online_cpus();
for_each_possible_cpu(cpu) {
:
}
put_online_cpus();
However, this lock has no protection with CPU hotplug since the ACPI
processor handler does not use the writer lock when it updates
cpu_possible_mask. The reader lock does not serialize within the
readers.
This patch protects them with the writer lock with cpu_hotplug_begin()
along with cpu_maps_update_begin(), which must be held before calling
cpu_hotplug_begin(). It also protects arch_register_cpu() /
arch_unregister_cpu(), which creates / deletes a sysfs cpu device
interface. For this purpose it changes cpu_hotplug_begin() and
cpu_hotplug_done() to global and exports them in cpu.h.
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2013-08-12 19:45:53 +04:00
void cpu_hotplug_done ( void )
2008-01-25 23:08:01 +03:00
{
cpu_hotplug . active_writer = NULL ;
mutex_unlock ( & cpu_hotplug . lock ) ;
2014-03-11 00:34:03 +04:00
cpuhp_lock_release ( ) ;
2008-01-25 23:08:01 +03:00
}
2010-05-27 01:43:36 +04:00
2013-06-13 01:04:36 +04:00
/*
* Wait for currently running CPU hotplug operations to complete ( if any ) and
* disable future CPU hotplug ( from sysfs ) . The ' cpu_add_remove_lock ' protects
* the ' cpu_hotplug_disabled ' flag . The same lock is also acquired by the
* hotplug path before performing hotplug operations . So acquiring that lock
* guarantees mutual exclusion from any currently running hotplug operations .
*/
void cpu_hotplug_disable ( void )
{
cpu_maps_update_begin ( ) ;
2015-08-05 10:52:46 +03:00
cpu_hotplug_disabled + + ;
2013-06-13 01:04:36 +04:00
cpu_maps_update_done ( ) ;
}
2015-08-05 10:52:47 +03:00
EXPORT_SYMBOL_GPL ( cpu_hotplug_disable ) ;
2013-06-13 01:04:36 +04:00
void cpu_hotplug_enable ( void )
{
cpu_maps_update_begin ( ) ;
2015-08-05 10:52:46 +03:00
WARN_ON ( - - cpu_hotplug_disabled < 0 ) ;
2013-06-13 01:04:36 +04:00
cpu_maps_update_done ( ) ;
}
2015-08-05 10:52:47 +03:00
EXPORT_SYMBOL_GPL ( cpu_hotplug_enable ) ;
ACPI / processor: Acquire writer lock to update CPU maps
CPU system maps are protected with reader/writer locks. The reader
lock, get_online_cpus(), assures that the maps are not updated while
holding the lock. The writer lock, cpu_hotplug_begin(), is used to
udpate the cpu maps along with cpu_maps_update_begin().
However, the ACPI processor handler updates the cpu maps without
holding the the writer lock.
acpi_map_lsapic() is called from acpi_processor_hotadd_init() to
update cpu_possible_mask and cpu_present_mask. acpi_unmap_lsapic()
is called from acpi_processor_remove() to update cpu_possible_mask.
Currently, they are either unprotected or protected with the reader
lock, which is not correct.
For example, the get_online_cpus() below is supposed to assure that
cpu_possible_mask is not changed while the code is iterating with
for_each_possible_cpu().
get_online_cpus();
for_each_possible_cpu(cpu) {
:
}
put_online_cpus();
However, this lock has no protection with CPU hotplug since the ACPI
processor handler does not use the writer lock when it updates
cpu_possible_mask. The reader lock does not serialize within the
readers.
This patch protects them with the writer lock with cpu_hotplug_begin()
along with cpu_maps_update_begin(), which must be held before calling
cpu_hotplug_begin(). It also protects arch_register_cpu() /
arch_unregister_cpu(), which creates / deletes a sysfs cpu device
interface. For this purpose it changes cpu_hotplug_begin() and
cpu_hotplug_done() to global and exports them in cpu.h.
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2013-08-12 19:45:53 +04:00
# endif /* CONFIG_HOTPLUG_CPU */
2010-05-27 01:43:36 +04:00
2005-04-17 02:20:36 +04:00
/* Need to know about CPUs going up/down? */
2015-07-19 21:06:22 +03:00
int register_cpu_notifier ( struct notifier_block * nb )
2005-04-17 02:20:36 +04:00
{
2006-10-17 11:10:35 +04:00
int ret ;
2008-01-25 23:08:01 +03:00
cpu_maps_update_begin ( ) ;
2006-10-17 11:10:35 +04:00
ret = raw_notifier_chain_register ( & cpu_chain , nb ) ;
2008-01-25 23:08:01 +03:00
cpu_maps_update_done ( ) ;
2006-10-17 11:10:35 +04:00
return ret ;
2005-04-17 02:20:36 +04:00
}
2006-06-27 13:54:08 +04:00
2015-07-19 21:06:22 +03:00
int __register_cpu_notifier ( struct notifier_block * nb )
CPU hotplug: Provide lockless versions of callback registration functions
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 00:34:14 +04:00
{
return raw_notifier_chain_register ( & cpu_chain , nb ) ;
}
2016-02-26 21:43:23 +03:00
static int __cpu_notify ( unsigned long val , unsigned int cpu , int nr_to_call ,
2010-05-27 01:43:28 +04:00
int * nr_calls )
{
2016-02-26 21:43:23 +03:00
unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0 ;
void * hcpu = ( void * ) ( long ) cpu ;
2010-05-27 01:43:29 +04:00
int ret ;
2016-02-26 21:43:23 +03:00
ret = __raw_notifier_call_chain ( & cpu_chain , val | mod , hcpu , nr_to_call ,
2010-05-27 01:43:28 +04:00
nr_calls ) ;
2010-05-27 01:43:29 +04:00
return notifier_to_errno ( ret ) ;
2010-05-27 01:43:28 +04:00
}
2016-02-26 21:43:23 +03:00
static int cpu_notify ( unsigned long val , unsigned int cpu )
2010-05-27 01:43:28 +04:00
{
2016-02-26 21:43:23 +03:00
return __cpu_notify ( val , cpu , - 1 , NULL ) ;
2010-05-27 01:43:28 +04:00
}
2016-02-26 21:43:24 +03:00
/* Notifier wrappers for transitioning to state machine */
static int notify_prepare ( unsigned int cpu )
{
int nr_calls = 0 ;
int ret ;
ret = __cpu_notify ( CPU_UP_PREPARE , cpu , - 1 , & nr_calls ) ;
if ( ret ) {
nr_calls - - ;
printk ( KERN_WARNING " %s: attempt to bring up CPU %u failed \n " ,
__func__ , cpu ) ;
__cpu_notify ( CPU_UP_CANCELED , cpu , nr_calls , NULL ) ;
}
return ret ;
}
static int notify_online ( unsigned int cpu )
{
cpu_notify ( CPU_ONLINE , cpu ) ;
return 0 ;
}
2016-02-26 21:43:29 +03:00
static int notify_starting ( unsigned int cpu )
{
cpu_notify ( CPU_STARTING , cpu ) ;
return 0 ;
}
2016-02-26 21:43:24 +03:00
static int bringup_cpu ( unsigned int cpu )
{
struct task_struct * idle = idle_thread_get ( cpu ) ;
int ret ;
/* Arch-specific enabling code. */
ret = __cpu_up ( cpu , idle ) ;
if ( ret ) {
cpu_notify ( CPU_UP_CANCELED , cpu ) ;
return ret ;
}
BUG_ON ( ! cpu_online ( cpu ) ) ;
return 0 ;
}
2016-02-26 21:43:37 +03:00
/*
* Hotplug state machine related functions
*/
static void undo_cpu_down ( unsigned int cpu , struct cpuhp_cpu_state * st ,
struct cpuhp_step * steps )
{
for ( st - > state + + ; st - > state < st - > target ; st - > state + + ) {
struct cpuhp_step * step = steps + st - > state ;
if ( ! step - > skip_onerr )
cpuhp_invoke_callback ( cpu , st - > state , step - > startup ) ;
}
}
static int cpuhp_down_callbacks ( unsigned int cpu , struct cpuhp_cpu_state * st ,
struct cpuhp_step * steps , enum cpuhp_state target )
{
enum cpuhp_state prev_state = st - > state ;
int ret = 0 ;
for ( ; st - > state > target ; st - > state - - ) {
struct cpuhp_step * step = steps + st - > state ;
ret = cpuhp_invoke_callback ( cpu , st - > state , step - > teardown ) ;
if ( ret ) {
st - > target = prev_state ;
undo_cpu_down ( cpu , st , steps ) ;
break ;
}
}
return ret ;
}
static void undo_cpu_up ( unsigned int cpu , struct cpuhp_cpu_state * st ,
struct cpuhp_step * steps )
{
for ( st - > state - - ; st - > state > st - > target ; st - > state - - ) {
struct cpuhp_step * step = steps + st - > state ;
if ( ! step - > skip_onerr )
cpuhp_invoke_callback ( cpu , st - > state , step - > teardown ) ;
}
}
static int cpuhp_up_callbacks ( unsigned int cpu , struct cpuhp_cpu_state * st ,
struct cpuhp_step * steps , enum cpuhp_state target )
{
enum cpuhp_state prev_state = st - > state ;
int ret = 0 ;
while ( st - > state < target ) {
struct cpuhp_step * step ;
st - > state + + ;
step = steps + st - > state ;
ret = cpuhp_invoke_callback ( cpu , st - > state , step - > startup ) ;
if ( ret ) {
st - > target = prev_state ;
undo_cpu_up ( cpu , st , steps ) ;
break ;
}
}
return ret ;
}
2016-02-26 21:43:38 +03:00
/*
* The cpu hotplug threads manage the bringup and teardown of the cpus
*/
static void cpuhp_create ( unsigned int cpu )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
init_completion ( & st - > done ) ;
}
static int cpuhp_should_run ( unsigned int cpu )
{
struct cpuhp_cpu_state * st = this_cpu_ptr ( & cpuhp_state ) ;
return st - > should_run ;
}
/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
static int cpuhp_ap_offline ( unsigned int cpu , struct cpuhp_cpu_state * st )
{
2016-02-26 21:43:39 +03:00
enum cpuhp_state target = max ( ( int ) st - > target , CPUHP_TEARDOWN_CPU ) ;
2016-02-26 21:43:38 +03:00
return cpuhp_down_callbacks ( cpu , st , cpuhp_ap_states , target ) ;
}
/* Execute the online startup callbacks. Used to be CPU_ONLINE */
static int cpuhp_ap_online ( unsigned int cpu , struct cpuhp_cpu_state * st )
{
return cpuhp_up_callbacks ( cpu , st , cpuhp_ap_states , st - > target ) ;
}
/*
* Execute teardown / startup callbacks on the plugged cpu . Also used to invoke
* callbacks when a state gets [ un ] installed at runtime .
*/
static void cpuhp_thread_fun ( unsigned int cpu )
{
struct cpuhp_cpu_state * st = this_cpu_ptr ( & cpuhp_state ) ;
int ret = 0 ;
/*
* Paired with the mb ( ) in cpuhp_kick_ap_work and
* cpuhp_invoke_ap_callback , so the work set is consistent visible .
*/
smp_mb ( ) ;
if ( ! st - > should_run )
return ;
st - > should_run = false ;
/* Single callback invocation for [un]install ? */
if ( st - > cb ) {
if ( st - > cb_state < CPUHP_AP_ONLINE ) {
local_irq_disable ( ) ;
ret = cpuhp_invoke_callback ( cpu , st - > cb_state , st - > cb ) ;
local_irq_enable ( ) ;
} else {
ret = cpuhp_invoke_callback ( cpu , st - > cb_state , st - > cb ) ;
}
} else {
2016-02-26 21:43:39 +03:00
/* Cannot happen .... */
BUG_ON ( st - > state < CPUHP_KICK_AP_THREAD ) ;
2016-02-26 21:43:38 +03:00
/* Regular hotplug work */
if ( st - > state < st - > target )
ret = cpuhp_ap_online ( cpu , st ) ;
else if ( st - > state > st - > target )
ret = cpuhp_ap_offline ( cpu , st ) ;
}
st - > result = ret ;
complete ( & st - > done ) ;
}
/* Invoke a single callback on a remote cpu */
static int cpuhp_invoke_ap_callback ( int cpu , enum cpuhp_state state ,
int ( * cb ) ( unsigned int ) )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
if ( ! cpu_online ( cpu ) )
return 0 ;
st - > cb_state = state ;
st - > cb = cb ;
/*
* Make sure the above stores are visible before should_run becomes
* true . Paired with the mb ( ) above in cpuhp_thread_fun ( )
*/
smp_mb ( ) ;
st - > should_run = true ;
wake_up_process ( st - > thread ) ;
wait_for_completion ( & st - > done ) ;
return st - > result ;
}
/* Regular hotplug invocation of the AP hotplug thread */
2016-02-26 21:43:39 +03:00
static void __cpuhp_kick_ap_work ( struct cpuhp_cpu_state * st )
2016-02-26 21:43:38 +03:00
{
st - > result = 0 ;
st - > cb = NULL ;
/*
* Make sure the above stores are visible before should_run becomes
* true . Paired with the mb ( ) above in cpuhp_thread_fun ( )
*/
smp_mb ( ) ;
st - > should_run = true ;
wake_up_process ( st - > thread ) ;
2016-02-26 21:43:39 +03:00
}
static int cpuhp_kick_ap_work ( unsigned int cpu )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
enum cpuhp_state state = st - > state ;
trace_cpuhp_enter ( cpu , st - > target , state , cpuhp_kick_ap_work ) ;
__cpuhp_kick_ap_work ( st ) ;
2016-02-26 21:43:38 +03:00
wait_for_completion ( & st - > done ) ;
trace_cpuhp_exit ( cpu , st - > state , state , st - > result ) ;
return st - > result ;
}
static struct smp_hotplug_thread cpuhp_threads = {
. store = & cpuhp_state . thread ,
. create = & cpuhp_create ,
. thread_should_run = cpuhp_should_run ,
. thread_fn = cpuhp_thread_fun ,
. thread_comm = " cpuhp/%u " ,
. selfparking = true ,
} ;
void __init cpuhp_threads_init ( void )
{
BUG_ON ( smpboot_register_percpu_thread ( & cpuhp_threads ) ) ;
kthread_unpark ( this_cpu_read ( cpuhp_state . thread ) ) ;
}
2010-05-27 21:32:08 +04:00
# ifdef CONFIG_HOTPLUG_CPU
2005-04-17 02:20:36 +04:00
EXPORT_SYMBOL ( register_cpu_notifier ) ;
CPU hotplug: Provide lockless versions of callback registration functions
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 00:34:14 +04:00
EXPORT_SYMBOL ( __register_cpu_notifier ) ;
2015-07-19 21:06:22 +03:00
void unregister_cpu_notifier ( struct notifier_block * nb )
2005-04-17 02:20:36 +04:00
{
2008-01-25 23:08:01 +03:00
cpu_maps_update_begin ( ) ;
2006-10-17 11:10:35 +04:00
raw_notifier_chain_unregister ( & cpu_chain , nb ) ;
2008-01-25 23:08:01 +03:00
cpu_maps_update_done ( ) ;
2005-04-17 02:20:36 +04:00
}
EXPORT_SYMBOL ( unregister_cpu_notifier ) ;
2015-07-19 21:06:22 +03:00
void __unregister_cpu_notifier ( struct notifier_block * nb )
CPU hotplug: Provide lockless versions of callback registration functions
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 00:34:14 +04:00
{
raw_notifier_chain_unregister ( & cpu_chain , nb ) ;
}
EXPORT_SYMBOL ( __unregister_cpu_notifier ) ;
2012-06-01 03:26:26 +04:00
/**
* clear_tasks_mm_cpumask - Safely clear tasks ' mm_cpumask for a CPU
* @ cpu : a CPU id
*
* This function walks all processes , finds a valid mm struct for each one and
* then clears a corresponding bit in mm ' s cpumask . While this all sounds
* trivial , there are various non - obvious corner cases , which this function
* tries to solve in a safe manner .
*
* Also note that the function uses a somewhat relaxed locking scheme , so it may
* be called only for an already offlined CPU .
*/
cpu: introduce clear_tasks_mm_cpumask() helper
Many architectures clear tasks' mm_cpumask like this:
read_lock(&tasklist_lock);
for_each_process(p) {
if (p->mm)
cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
}
read_unlock(&tasklist_lock);
Depending on the context, the code above may have several problems,
such as:
1. Working with task->mm w/o getting mm or grabing the task lock is
dangerous as ->mm might disappear (exit_mm() assigns NULL under
task_lock(), so tasklist lock is not enough).
2. Checking for process->mm is not enough because process' main
thread may exit or detach its mm via use_mm(), but other threads
may still have a valid mm.
This patch implements a small helper function that does things
correctly, i.e.:
1. We take the task's lock while whe handle its mm (we can't use
get_task_mm()/mmput() pair as mmput() might sleep);
2. To catch exited main thread case, we use find_lock_task_mm(),
which walks up all threads and returns an appropriate task
(with task lock held).
Also, Per Peter Zijlstra's idea, now we don't grab tasklist_lock in
the new helper, instead we take the rcu read lock. We can do this
because the function is called after the cpu is taken down and marked
offline, so no new tasks will get this cpu set in their mm mask.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-01 03:26:22 +04:00
void clear_tasks_mm_cpumask ( int cpu )
{
struct task_struct * p ;
/*
* This function is called after the cpu is taken down and marked
* offline , so its not like new tasks will ever get this cpu set in
* their mm mask . - - Peter Zijlstra
* Thus , we may use rcu_read_lock ( ) here , instead of grabbing
* full - fledged tasklist_lock .
*/
2012-06-01 03:26:26 +04:00
WARN_ON ( cpu_online ( cpu ) ) ;
cpu: introduce clear_tasks_mm_cpumask() helper
Many architectures clear tasks' mm_cpumask like this:
read_lock(&tasklist_lock);
for_each_process(p) {
if (p->mm)
cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
}
read_unlock(&tasklist_lock);
Depending on the context, the code above may have several problems,
such as:
1. Working with task->mm w/o getting mm or grabing the task lock is
dangerous as ->mm might disappear (exit_mm() assigns NULL under
task_lock(), so tasklist lock is not enough).
2. Checking for process->mm is not enough because process' main
thread may exit or detach its mm via use_mm(), but other threads
may still have a valid mm.
This patch implements a small helper function that does things
correctly, i.e.:
1. We take the task's lock while whe handle its mm (we can't use
get_task_mm()/mmput() pair as mmput() might sleep);
2. To catch exited main thread case, we use find_lock_task_mm(),
which walks up all threads and returns an appropriate task
(with task lock held).
Also, Per Peter Zijlstra's idea, now we don't grab tasklist_lock in
the new helper, instead we take the rcu read lock. We can do this
because the function is called after the cpu is taken down and marked
offline, so no new tasks will get this cpu set in their mm mask.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-01 03:26:22 +04:00
rcu_read_lock ( ) ;
for_each_process ( p ) {
struct task_struct * t ;
2012-06-01 03:26:26 +04:00
/*
* Main thread might exit , but other threads may still have
* a valid mm . Find one .
*/
cpu: introduce clear_tasks_mm_cpumask() helper
Many architectures clear tasks' mm_cpumask like this:
read_lock(&tasklist_lock);
for_each_process(p) {
if (p->mm)
cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
}
read_unlock(&tasklist_lock);
Depending on the context, the code above may have several problems,
such as:
1. Working with task->mm w/o getting mm or grabing the task lock is
dangerous as ->mm might disappear (exit_mm() assigns NULL under
task_lock(), so tasklist lock is not enough).
2. Checking for process->mm is not enough because process' main
thread may exit or detach its mm via use_mm(), but other threads
may still have a valid mm.
This patch implements a small helper function that does things
correctly, i.e.:
1. We take the task's lock while whe handle its mm (we can't use
get_task_mm()/mmput() pair as mmput() might sleep);
2. To catch exited main thread case, we use find_lock_task_mm(),
which walks up all threads and returns an appropriate task
(with task lock held).
Also, Per Peter Zijlstra's idea, now we don't grab tasklist_lock in
the new helper, instead we take the rcu read lock. We can do this
because the function is called after the cpu is taken down and marked
offline, so no new tasks will get this cpu set in their mm mask.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-01 03:26:22 +04:00
t = find_lock_task_mm ( p ) ;
if ( ! t )
continue ;
cpumask_clear_cpu ( cpu , mm_cpumask ( t - > mm ) ) ;
task_unlock ( t ) ;
}
rcu_read_unlock ( ) ;
}
2014-06-25 12:19:55 +04:00
static inline void check_for_tasks ( int dead_cpu )
2005-04-17 02:20:36 +04:00
{
2014-06-25 12:19:55 +04:00
struct task_struct * g , * p ;
2005-04-17 02:20:36 +04:00
2015-09-10 16:07:50 +03:00
read_lock ( & tasklist_lock ) ;
for_each_process_thread ( g , p ) {
2014-06-25 12:19:55 +04:00
if ( ! p - > on_rq )
continue ;
/*
* We do the check with unlocked task_rq ( p ) - > lock .
* Order the reading to do not warn about a task ,
* which was running on this cpu in the past , and
* it ' s just been woken on another cpu .
*/
rmb ( ) ;
if ( task_cpu ( p ) ! = dead_cpu )
continue ;
pr_warn ( " Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x) \n " ,
p - > comm , task_pid_nr ( p ) , dead_cpu , p - > state , p - > flags ) ;
2015-09-10 16:07:50 +03:00
}
read_unlock ( & tasklist_lock ) ;
2005-04-17 02:20:36 +04:00
}
2016-02-26 21:43:25 +03:00
static void cpu_notify_nofail ( unsigned long val , unsigned int cpu )
{
BUG_ON ( cpu_notify ( val , cpu ) ) ;
}
static int notify_down_prepare ( unsigned int cpu )
{
int err , nr_calls = 0 ;
err = __cpu_notify ( CPU_DOWN_PREPARE , cpu , - 1 , & nr_calls ) ;
if ( err ) {
nr_calls - - ;
__cpu_notify ( CPU_DOWN_FAILED , cpu , nr_calls , NULL ) ;
pr_warn ( " %s: attempt to take down CPU %u failed \n " ,
__func__ , cpu ) ;
}
return err ;
}
2016-02-26 21:43:29 +03:00
static int notify_dying ( unsigned int cpu )
{
cpu_notify ( CPU_DYING , cpu ) ;
return 0 ;
}
2005-04-17 02:20:36 +04:00
/* Take this CPU down. */
2015-07-19 21:06:22 +03:00
static int take_cpu_down ( void * _param )
2005-04-17 02:20:36 +04:00
{
2016-02-26 21:43:29 +03:00
struct cpuhp_cpu_state * st = this_cpu_ptr ( & cpuhp_state ) ;
enum cpuhp_state target = max ( ( int ) st - > target , CPUHP_AP_OFFLINE ) ;
2016-02-26 21:43:23 +03:00
int err , cpu = smp_processor_id ( ) ;
2005-04-17 02:20:36 +04:00
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable ( ) ;
if ( err < 0 )
2005-06-26 01:54:50 +04:00
return err ;
2005-04-17 02:20:36 +04:00
2016-02-26 21:43:29 +03:00
/* Invoke the former CPU_DYING callbacks */
for ( ; st - > state > target ; st - > state - - ) {
struct cpuhp_step * step = cpuhp_ap_states + st - > state ;
cpuhp_invoke_callback ( cpu , st - > state , step - > teardown ) ;
}
2015-04-03 03:37:24 +03:00
/* Give up timekeeping duties */
tick_handover_do_timer ( ) ;
2013-01-31 16:11:14 +04:00
/* Park the stopper thread */
2016-02-26 21:43:23 +03:00
stop_machine_park ( cpu ) ;
2005-06-26 01:54:50 +04:00
return 0 ;
2005-04-17 02:20:36 +04:00
}
2016-02-26 21:43:25 +03:00
static int takedown_cpu ( unsigned int cpu )
2005-04-17 02:20:36 +04:00
{
2016-02-26 21:43:25 +03:00
int err ;
2005-04-17 02:20:36 +04:00
2013-10-11 16:38:20 +04:00
/*
* By now we ' ve cleared cpu_active_mask , wait for all preempt - disabled
* and RCU users of this state to go away such that all new such users
* will observe it .
*
* For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu ( ) might
2015-06-10 23:34:41 +03:00
* not imply sync_sched ( ) , so wait for both .
2013-11-13 07:10:56 +04:00
*
* Do sync before park smpboot threads to take care the rcu boost case .
2013-10-11 16:38:20 +04:00
*/
2015-06-10 23:34:41 +03:00
if ( IS_ENABLED ( CONFIG_PREEMPT ) )
synchronize_rcu_mult ( call_rcu , call_rcu_sched ) ;
else
synchronize_rcu ( ) ;
2013-10-11 16:38:20 +04:00
2016-02-26 21:43:39 +03:00
/* Park the hotplug thread */
kthread_park ( per_cpu_ptr ( & cpuhp_state , cpu ) - > thread ) ;
2013-10-11 16:38:20 +04:00
/*
2015-07-05 20:12:30 +03:00
* Prevent irq alloc / free while the dying cpu reorganizes the
* interrupt affinities .
2013-10-11 16:38:20 +04:00
*/
2015-07-05 20:12:30 +03:00
irq_lock_sparse ( ) ;
2013-10-11 16:38:20 +04:00
2015-07-05 20:12:30 +03:00
/*
* So now all preempt / rcu users must observe ! cpu_active ( ) .
*/
2016-02-26 21:43:23 +03:00
err = stop_machine ( take_cpu_down , NULL , cpumask_of ( cpu ) ) ;
2008-07-28 21:16:29 +04:00
if ( err ) {
2005-04-17 02:20:36 +04:00
/* CPU didn't die: tell everyone. Can't complain. */
2016-02-26 21:43:23 +03:00
cpu_notify_nofail ( CPU_DOWN_FAILED , cpu ) ;
2015-07-05 20:12:30 +03:00
irq_unlock_sparse ( ) ;
2016-02-26 21:43:25 +03:00
return err ;
2006-10-28 21:38:57 +04:00
}
2008-07-28 21:16:29 +04:00
BUG_ON ( cpu_online ( cpu ) ) ;
2005-04-17 02:20:36 +04:00
2010-11-13 21:32:29 +03:00
/*
* The migration_call ( ) CPU_DYING callback will have removed all
* runnable tasks from the cpu , there ' s only the idle task left now
* that the migration thread is done doing the stop_machine thing .
2010-11-19 22:37:53 +03:00
*
* Wait for the stop thread to go away .
2010-11-13 21:32:29 +03:00
*/
2015-01-29 01:09:43 +03:00
while ( ! per_cpu ( cpu_dead_idle , cpu ) )
2010-11-19 22:37:53 +03:00
cpu_relax ( ) ;
2015-01-29 01:09:43 +03:00
smp_mb ( ) ; /* Read from cpu_dead_idle before __cpu_die(). */
per_cpu ( cpu_dead_idle , cpu ) = false ;
2005-04-17 02:20:36 +04:00
2015-07-05 20:12:30 +03:00
/* Interrupts are moved away from the dying cpu, reenable alloc/free */
irq_unlock_sparse ( ) ;
2015-03-30 12:29:19 +03:00
hotplug_cpu__broadcast_tick_pull ( cpu ) ;
2005-04-17 02:20:36 +04:00
/* This actually kills the CPU. */
__cpu_die ( cpu ) ;
2015-04-03 03:38:05 +03:00
tick_cleanup_dead_cpu ( cpu ) ;
2016-02-26 21:43:25 +03:00
return 0 ;
}
2005-04-17 02:20:36 +04:00
2016-02-26 21:43:25 +03:00
static int notify_dead ( unsigned int cpu )
{
cpu_notify_nofail ( CPU_DEAD , cpu ) ;
2005-04-17 02:20:36 +04:00
check_for_tasks ( cpu ) ;
2016-02-26 21:43:25 +03:00
return 0 ;
}
2016-02-26 21:43:28 +03:00
# else
# define notify_down_prepare NULL
# define takedown_cpu NULL
# define notify_dead NULL
2016-02-26 21:43:29 +03:00
# define notify_dying NULL
2016-02-26 21:43:28 +03:00
# endif
# ifdef CONFIG_HOTPLUG_CPU
2016-02-26 21:43:25 +03:00
/* Requires cpu_add_remove_lock to be held */
2016-02-26 21:43:30 +03:00
static int __ref _cpu_down ( unsigned int cpu , int tasks_frozen ,
enum cpuhp_state target )
2016-02-26 21:43:25 +03:00
{
2016-02-26 21:43:28 +03:00
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
int prev_state , ret = 0 ;
bool hasdied = false ;
2016-02-26 21:43:25 +03:00
if ( num_online_cpus ( ) = = 1 )
return - EBUSY ;
2016-02-26 21:43:32 +03:00
if ( ! cpu_present ( cpu ) )
2016-02-26 21:43:25 +03:00
return - EINVAL ;
cpu_hotplug_begin ( ) ;
cpuhp_tasks_frozen = tasks_frozen ;
2016-02-26 21:43:28 +03:00
prev_state = st - > state ;
2016-02-26 21:43:30 +03:00
st - > target = target ;
2016-02-26 21:43:39 +03:00
/*
* If the current CPU state is in the range of the AP hotplug thread ,
* then we need to kick the thread .
*/
if ( st - > state > = CPUHP_KICK_AP_THREAD ) {
ret = cpuhp_kick_ap_work ( cpu ) ;
/*
* The AP side has done the error rollback already . Just
* return the error code . .
*/
if ( ret )
goto out ;
/*
* We might have stopped still in the range of the AP hotplug
* thread . Nothing to do anymore .
*/
if ( st - > state > = CPUHP_KICK_AP_THREAD )
goto out ;
}
/*
* The AP brought itself down below CPUHP_KICK_AP_THREAD . So we need
* to do the further cleanups .
*/
2016-02-26 21:43:37 +03:00
ret = cpuhp_down_callbacks ( cpu , st , cpuhp_bp_states , target ) ;
2016-02-26 21:43:25 +03:00
2016-02-26 21:43:28 +03:00
hasdied = prev_state ! = st - > state & & st - > state = = CPUHP_OFFLINE ;
2016-02-26 21:43:39 +03:00
out :
2008-01-25 23:08:01 +03:00
cpu_hotplug_done ( ) ;
2016-02-26 21:43:28 +03:00
/* This post dead nonsense must die */
if ( ! ret & & hasdied )
2016-02-26 21:43:23 +03:00
cpu_notify_nofail ( CPU_POST_DEAD , cpu ) ;
2016-02-26 21:43:28 +03:00
return ret ;
2006-09-26 10:32:48 +04:00
}
2016-02-26 21:43:30 +03:00
static int do_cpu_down ( unsigned int cpu , enum cpuhp_state target )
2006-09-26 10:32:48 +04:00
{
2008-12-22 14:36:30 +03:00
int err ;
2006-09-26 10:32:48 +04:00
2008-01-25 23:08:01 +03:00
cpu_maps_update_begin ( ) ;
2008-07-15 15:43:49 +04:00
if ( cpu_hotplug_disabled ) {
2006-09-26 10:32:48 +04:00
err = - EBUSY ;
2008-07-15 15:43:49 +04:00
goto out ;
}
2016-02-26 21:43:30 +03:00
err = _cpu_down ( cpu , 0 , target ) ;
2006-09-26 10:32:48 +04:00
2008-07-15 15:43:49 +04:00
out :
2008-01-25 23:08:01 +03:00
cpu_maps_update_done ( ) ;
2005-04-17 02:20:36 +04:00
return err ;
}
2016-02-26 21:43:30 +03:00
int cpu_down ( unsigned int cpu )
{
return do_cpu_down ( cpu , CPUHP_OFFLINE ) ;
}
2008-04-29 10:35:56 +04:00
EXPORT_SYMBOL ( cpu_down ) ;
2005-04-17 02:20:36 +04:00
# endif /*CONFIG_HOTPLUG_CPU*/
2016-02-26 21:43:29 +03:00
/**
* notify_cpu_starting ( cpu ) - call the CPU_STARTING notifiers
* @ cpu : cpu that just started
*
* This function calls the cpu_chain notifiers with CPU_STARTING .
* It must be called by the arch code on the new cpu , before the new cpu
* enables interrupts and before the " boot " cpu returns from __cpu_up ( ) .
*/
void notify_cpu_starting ( unsigned int cpu )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
enum cpuhp_state target = min ( ( int ) st - > target , CPUHP_AP_ONLINE ) ;
while ( st - > state < target ) {
struct cpuhp_step * step ;
st - > state + + ;
step = cpuhp_ap_states + st - > state ;
cpuhp_invoke_callback ( cpu , st - > state , step - > startup ) ;
}
}
2016-02-26 21:43:35 +03:00
/*
* Called from the idle task . We need to set active here , so we can kick off
* the stopper thread .
*/
static int cpuhp_set_cpu_active ( unsigned int cpu )
{
2016-02-26 21:43:39 +03:00
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
2016-02-26 21:43:35 +03:00
/* The cpu is marked online, set it active now */
set_cpu_active ( cpu , true ) ;
2016-02-26 21:43:39 +03:00
/* Unpark the stopper thread and the hotplug thread */
2016-02-26 21:43:35 +03:00
stop_machine_unpark ( cpu ) ;
2016-02-26 21:43:39 +03:00
kthread_unpark ( st - > thread ) ;
2016-02-26 21:43:35 +03:00
return 0 ;
}
2006-09-26 10:32:48 +04:00
/* Requires cpu_add_remove_lock to be held */
2016-02-26 21:43:30 +03:00
static int _cpu_up ( unsigned int cpu , int tasks_frozen , enum cpuhp_state target )
2005-04-17 02:20:36 +04:00
{
2016-02-26 21:43:28 +03:00
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
2012-04-21 04:08:50 +04:00
struct task_struct * idle ;
2016-02-26 21:43:37 +03:00
int ret = 0 ;
2005-04-17 02:20:36 +04:00
2008-01-25 23:08:01 +03:00
cpu_hotplug_begin ( ) ;
2012-04-20 17:05:44 +04:00
2016-02-26 21:43:32 +03:00
if ( ! cpu_present ( cpu ) ) {
2012-10-23 03:30:54 +04:00
ret = - EINVAL ;
goto out ;
}
2016-02-26 21:43:32 +03:00
/*
* The caller of do_cpu_up might have raced with another
* caller . Ignore it for now .
*/
if ( st - > state > = target )
2012-04-20 17:05:44 +04:00
goto out ;
2016-02-26 21:43:32 +03:00
if ( st - > state = = CPUHP_OFFLINE ) {
/* Let it fail before we try to bring the cpu up */
idle = idle_thread_get ( cpu ) ;
if ( IS_ERR ( idle ) ) {
ret = PTR_ERR ( idle ) ;
goto out ;
}
2012-04-21 04:08:50 +04:00
}
2012-04-20 17:05:44 +04:00
2016-02-26 21:43:24 +03:00
cpuhp_tasks_frozen = tasks_frozen ;
2016-02-26 21:43:30 +03:00
st - > target = target ;
2016-02-26 21:43:39 +03:00
/*
* If the current CPU state is in the range of the AP hotplug thread ,
* then we need to kick the thread once more .
*/
if ( st - > state > = CPUHP_KICK_AP_THREAD ) {
ret = cpuhp_kick_ap_work ( cpu ) ;
/*
* The AP side has done the error rollback already . Just
* return the error code . .
*/
if ( ret )
goto out ;
}
/*
* Try to reach the target state . We max out on the BP at
* CPUHP_KICK_AP_THREAD . After that the AP hotplug thread is
* responsible for bringing it up to the target state .
*/
target = min ( ( int ) target , CPUHP_KICK_AP_THREAD ) ;
2016-02-26 21:43:37 +03:00
ret = cpuhp_up_callbacks ( cpu , st , cpuhp_bp_states , target ) ;
2012-04-20 17:05:44 +04:00
out :
2008-01-25 23:08:01 +03:00
cpu_hotplug_done ( ) ;
2006-09-26 10:32:48 +04:00
return ret ;
}
2016-02-26 21:43:30 +03:00
static int do_cpu_up ( unsigned int cpu , enum cpuhp_state target )
2006-09-26 10:32:48 +04:00
{
int err = 0 ;
2010-05-25 01:32:41 +04:00
2009-01-01 02:42:28 +03:00
if ( ! cpu_possible ( cpu ) ) {
2014-06-05 03:11:17 +04:00
pr_err ( " can't online cpu %d because it is not configured as may-hotadd at boot time \n " ,
cpu ) ;
2010-03-06 00:42:38 +03:00
# if defined(CONFIG_IA64)
2014-06-05 03:11:17 +04:00
pr_err ( " please check additional_cpus= boot parameter \n " ) ;
2007-10-19 10:40:47 +04:00
# endif
return - EINVAL ;
}
2006-09-26 10:32:48 +04:00
2013-11-13 03:07:25 +04:00
err = try_online_node ( cpu_to_node ( cpu ) ) ;
if ( err )
return err ;
2010-05-25 01:32:41 +04:00
2008-01-25 23:08:01 +03:00
cpu_maps_update_begin ( ) ;
2008-07-15 15:43:49 +04:00
if ( cpu_hotplug_disabled ) {
2006-09-26 10:32:48 +04:00
err = - EBUSY ;
2008-07-15 15:43:49 +04:00
goto out ;
}
2016-02-26 21:43:30 +03:00
err = _cpu_up ( cpu , 0 , target ) ;
2008-07-15 15:43:49 +04:00
out :
2008-01-25 23:08:01 +03:00
cpu_maps_update_done ( ) ;
2006-09-26 10:32:48 +04:00
return err ;
}
2016-02-26 21:43:30 +03:00
int cpu_up ( unsigned int cpu )
{
return do_cpu_up ( cpu , CPUHP_ONLINE ) ;
}
2011-12-12 09:54:45 +04:00
EXPORT_SYMBOL_GPL ( cpu_up ) ;
2006-09-26 10:32:48 +04:00
2007-08-31 10:56:29 +04:00
# ifdef CONFIG_PM_SLEEP_SMP
2009-01-01 02:42:28 +03:00
static cpumask_var_t frozen_cpus ;
2006-09-26 10:32:48 +04:00
int disable_nonboot_cpus ( void )
{
2010-05-28 00:16:22 +04:00
int cpu , first_cpu , error = 0 ;
2006-09-26 10:32:48 +04:00
2008-01-25 23:08:01 +03:00
cpu_maps_update_begin ( ) ;
2009-01-01 02:42:28 +03:00
first_cpu = cpumask_first ( cpu_online_mask ) ;
2009-12-16 20:04:32 +03:00
/*
* We take down all of the non - boot CPUs in one shot to avoid races
2006-09-26 10:32:48 +04:00
* with the userspace trying to use the CPU hotplug at the same time
*/
2009-01-01 02:42:28 +03:00
cpumask_clear ( frozen_cpus ) ;
2009-11-25 15:31:39 +03:00
2014-06-05 03:11:17 +04:00
pr_info ( " Disabling non-boot CPUs ... \n " ) ;
2006-09-26 10:32:48 +04:00
for_each_online_cpu ( cpu ) {
if ( cpu = = first_cpu )
continue ;
2014-06-06 16:40:17 +04:00
trace_suspend_resume ( TPS ( " CPU_OFF " ) , cpu , true ) ;
2016-02-26 21:43:30 +03:00
error = _cpu_down ( cpu , 1 , CPUHP_OFFLINE ) ;
2014-06-06 16:40:17 +04:00
trace_suspend_resume ( TPS ( " CPU_OFF " ) , cpu , false ) ;
2009-11-18 03:22:13 +03:00
if ( ! error )
2009-01-01 02:42:28 +03:00
cpumask_set_cpu ( cpu , frozen_cpus ) ;
2009-11-18 03:22:13 +03:00
else {
2014-06-05 03:11:17 +04:00
pr_err ( " Error taking CPU%d down: %d \n " , cpu , error ) ;
2006-09-26 10:32:48 +04:00
break ;
}
}
2009-07-01 06:31:07 +04:00
2015-08-05 10:52:46 +03:00
if ( ! error )
2006-09-26 10:32:48 +04:00
BUG_ON ( num_online_cpus ( ) > 1 ) ;
2015-08-05 10:52:46 +03:00
else
2014-06-05 03:11:17 +04:00
pr_err ( " Non-boot CPUs are not disabled \n " ) ;
2015-08-05 10:52:46 +03:00
/*
* Make sure the CPUs won ' t be enabled by someone else . We need to do
* this even in case of failure as all disable_nonboot_cpus ( ) users are
* supposed to do enable_nonboot_cpus ( ) on the failure path .
*/
cpu_hotplug_disabled + + ;
2008-01-25 23:08:01 +03:00
cpu_maps_update_done ( ) ;
2006-09-26 10:32:48 +04:00
return error ;
}
2009-08-20 05:05:36 +04:00
void __weak arch_enable_nonboot_cpus_begin ( void )
{
}
void __weak arch_enable_nonboot_cpus_end ( void )
{
}
2015-07-19 21:06:22 +03:00
void enable_nonboot_cpus ( void )
2006-09-26 10:32:48 +04:00
{
int cpu , error ;
/* Allow everyone to use the CPU hotplug again */
2008-01-25 23:08:01 +03:00
cpu_maps_update_begin ( ) ;
2015-08-05 10:52:46 +03:00
WARN_ON ( - - cpu_hotplug_disabled < 0 ) ;
2009-01-01 02:42:28 +03:00
if ( cpumask_empty ( frozen_cpus ) )
2007-04-02 10:49:49 +04:00
goto out ;
2006-09-26 10:32:48 +04:00
2014-06-05 03:11:17 +04:00
pr_info ( " Enabling non-boot CPUs ... \n " ) ;
2009-08-20 05:05:36 +04:00
arch_enable_nonboot_cpus_begin ( ) ;
2009-01-01 02:42:28 +03:00
for_each_cpu ( cpu , frozen_cpus ) {
2014-06-06 16:40:17 +04:00
trace_suspend_resume ( TPS ( " CPU_ON " ) , cpu , true ) ;
2016-02-26 21:43:30 +03:00
error = _cpu_up ( cpu , 1 , CPUHP_ONLINE ) ;
2014-06-06 16:40:17 +04:00
trace_suspend_resume ( TPS ( " CPU_ON " ) , cpu , false ) ;
2006-09-26 10:32:48 +04:00
if ( ! error ) {
2014-06-05 03:11:17 +04:00
pr_info ( " CPU%d is up \n " , cpu ) ;
2006-09-26 10:32:48 +04:00
continue ;
}
2014-06-05 03:11:17 +04:00
pr_warn ( " Error taking CPU%d up: %d \n " , cpu , error ) ;
2006-09-26 10:32:48 +04:00
}
2009-08-20 05:05:36 +04:00
arch_enable_nonboot_cpus_end ( ) ;
2009-01-01 02:42:28 +03:00
cpumask_clear ( frozen_cpus ) ;
2007-04-02 10:49:49 +04:00
out :
2008-01-25 23:08:01 +03:00
cpu_maps_update_done ( ) ;
2005-04-17 02:20:36 +04:00
}
2009-01-01 02:42:28 +03:00
2011-11-16 00:59:31 +04:00
static int __init alloc_frozen_cpus ( void )
2009-01-01 02:42:28 +03:00
{
if ( ! alloc_cpumask_var ( & frozen_cpus , GFP_KERNEL | __GFP_ZERO ) )
return - ENOMEM ;
return 0 ;
}
core_initcall ( alloc_frozen_cpus ) ;
2011-11-03 03:59:25 +04:00
/*
* When callbacks for CPU hotplug notifications are being executed , we must
* ensure that the state of the system with respect to the tasks being frozen
* or not , as reported by the notification , remains unchanged * throughout the
* duration * of the execution of the callbacks .
* Hence we need to prevent the freezer from racing with regular CPU hotplug .
*
* This synchronization is implemented by mutually excluding regular CPU
* hotplug and Suspend / Hibernate call paths by hooking onto the Suspend /
* Hibernate notifications .
*/
static int
cpu_hotplug_pm_callback ( struct notifier_block * nb ,
unsigned long action , void * ptr )
{
switch ( action ) {
case PM_SUSPEND_PREPARE :
case PM_HIBERNATION_PREPARE :
2013-06-13 01:04:36 +04:00
cpu_hotplug_disable ( ) ;
2011-11-03 03:59:25 +04:00
break ;
case PM_POST_SUSPEND :
case PM_POST_HIBERNATION :
2013-06-13 01:04:36 +04:00
cpu_hotplug_enable ( ) ;
2011-11-03 03:59:25 +04:00
break ;
default :
return NOTIFY_DONE ;
}
return NOTIFY_OK ;
}
2011-11-16 00:59:31 +04:00
static int __init cpu_hotplug_pm_sync_init ( void )
2011-11-03 03:59:25 +04:00
{
2012-11-13 23:32:43 +04:00
/*
* cpu_hotplug_pm_callback has higher priority than x86
* bsp_pm_callback which depends on cpu_hotplug_pm_callback
* to disable cpu hotplug to avoid cpu hotplug race .
*/
2011-11-03 03:59:25 +04:00
pm_notifier ( cpu_hotplug_pm_callback , 0 ) ;
return 0 ;
}
core_initcall ( cpu_hotplug_pm_sync_init ) ;
2007-08-31 10:56:29 +04:00
# endif /* CONFIG_PM_SLEEP_SMP */
2008-05-29 22:17:02 +04:00
# endif /* CONFIG_SMP */
2008-07-25 05:21:29 +04:00
2016-02-26 21:43:28 +03:00
/* Boot processor state steps */
static struct cpuhp_step cpuhp_bp_states [ ] = {
[ CPUHP_OFFLINE ] = {
. name = " offline " ,
. startup = NULL ,
. teardown = NULL ,
} ,
# ifdef CONFIG_SMP
[ CPUHP_CREATE_THREADS ] = {
. name = " threads:create " ,
. startup = smpboot_create_threads ,
. teardown = NULL ,
2016-02-26 21:43:32 +03:00
. cant_stop = true ,
2016-02-26 21:43:28 +03:00
} ,
[ CPUHP_NOTIFY_PREPARE ] = {
. name = " notify:prepare " ,
. startup = notify_prepare ,
. teardown = notify_dead ,
. skip_onerr = true ,
2016-02-26 21:43:32 +03:00
. cant_stop = true ,
2016-02-26 21:43:28 +03:00
} ,
[ CPUHP_BRINGUP_CPU ] = {
. name = " cpu:bringup " ,
. startup = bringup_cpu ,
2016-02-26 21:43:29 +03:00
. teardown = NULL ,
2016-02-26 21:43:32 +03:00
. cant_stop = true ,
2016-02-26 21:43:29 +03:00
} ,
[ CPUHP_TEARDOWN_CPU ] = {
. name = " cpu:teardown " ,
. startup = NULL ,
2016-02-26 21:43:28 +03:00
. teardown = takedown_cpu ,
2016-02-26 21:43:32 +03:00
. cant_stop = true ,
2016-02-26 21:43:28 +03:00
} ,
2016-02-26 21:43:35 +03:00
[ CPUHP_CPU_SET_ACTIVE ] = {
. name = " cpu:active " ,
. startup = cpuhp_set_cpu_active ,
. teardown = NULL ,
} ,
2016-02-26 21:43:39 +03:00
[ CPUHP_KICK_AP_THREAD ] = {
. name = " cpuhp:kickthread " ,
. startup = cpuhp_kick_ap_work ,
. teardown = cpuhp_kick_ap_work ,
2016-02-26 21:43:28 +03:00
} ,
# endif
2016-02-26 21:43:39 +03:00
[ CPUHP_BP_ONLINE ] = {
2016-02-26 21:43:28 +03:00
. name = " online " ,
. startup = NULL ,
. teardown = NULL ,
} ,
} ;
2016-02-26 21:43:29 +03:00
/* Application processor state steps */
static struct cpuhp_step cpuhp_ap_states [ ] = {
# ifdef CONFIG_SMP
[ CPUHP_AP_NOTIFY_STARTING ] = {
. name = " notify:starting " ,
. startup = notify_starting ,
. teardown = notify_dying ,
. skip_onerr = true ,
2016-02-26 21:43:32 +03:00
. cant_stop = true ,
2016-02-26 21:43:29 +03:00
} ,
2016-02-26 21:43:39 +03:00
[ CPUHP_AP_SMPBOOT_THREADS ] = {
. name = " smpboot:threads " ,
. startup = smpboot_unpark_threads ,
. teardown = smpboot_park_threads ,
} ,
[ CPUHP_AP_NOTIFY_ONLINE ] = {
. name = " notify:online " ,
. startup = notify_online ,
. teardown = notify_down_prepare ,
} ,
2016-02-26 21:43:29 +03:00
# endif
[ CPUHP_ONLINE ] = {
. name = " online " ,
. startup = NULL ,
. teardown = NULL ,
} ,
} ;
2016-02-26 21:43:33 +03:00
/* Sanity check for callbacks */
static int cpuhp_cb_check ( enum cpuhp_state state )
{
if ( state < = CPUHP_OFFLINE | | state > = CPUHP_ONLINE )
return - EINVAL ;
return 0 ;
}
2016-02-26 21:43:31 +03:00
static bool cpuhp_is_ap_state ( enum cpuhp_state state )
{
2016-02-26 21:43:39 +03:00
if ( state > = CPUHP_AP_OFFLINE & & state < = CPUHP_AP_ONLINE )
return true ;
return state > CPUHP_BP_ONLINE ;
2016-02-26 21:43:31 +03:00
}
static struct cpuhp_step * cpuhp_get_step ( enum cpuhp_state state )
{
struct cpuhp_step * sp ;
sp = cpuhp_is_ap_state ( state ) ? cpuhp_ap_states : cpuhp_bp_states ;
return sp + state ;
}
2016-02-26 21:43:33 +03:00
static void cpuhp_store_callbacks ( enum cpuhp_state state ,
const char * name ,
int ( * startup ) ( unsigned int cpu ) ,
int ( * teardown ) ( unsigned int cpu ) )
{
/* (Un)Install the callbacks for further cpu hotplug operations */
struct cpuhp_step * sp ;
mutex_lock ( & cpuhp_state_mutex ) ;
sp = cpuhp_get_step ( state ) ;
sp - > startup = startup ;
sp - > teardown = teardown ;
sp - > name = name ;
mutex_unlock ( & cpuhp_state_mutex ) ;
}
static void * cpuhp_get_teardown_cb ( enum cpuhp_state state )
{
return cpuhp_get_step ( state ) - > teardown ;
}
/*
* Call the startup / teardown function for a step either on the AP or
* on the current CPU .
*/
static int cpuhp_issue_call ( int cpu , enum cpuhp_state state ,
int ( * cb ) ( unsigned int ) , bool bringup )
{
int ret ;
if ( ! cb )
return 0 ;
/*
* The non AP bound callbacks can fail on bringup . On teardown
* e . g . module removal we crash for now .
*/
2016-02-26 21:43:39 +03:00
# ifdef CONFIG_SMP
if ( cpuhp_is_ap_state ( state ) )
ret = cpuhp_invoke_ap_callback ( cpu , state , cb ) ;
else
ret = cpuhp_invoke_callback ( cpu , state , cb ) ;
# else
ret = cpuhp_invoke_callback ( cpu , state , cb ) ;
# endif
2016-02-26 21:43:33 +03:00
BUG_ON ( ret & & ! bringup ) ;
return ret ;
}
/*
* Called from __cpuhp_setup_state on a recoverable failure .
*
* Note : The teardown callbacks for rollback are not allowed to fail !
*/
static void cpuhp_rollback_install ( int failedcpu , enum cpuhp_state state ,
int ( * teardown ) ( unsigned int cpu ) )
{
int cpu ;
if ( ! teardown )
return ;
/* Roll back the already executed steps on the other cpus */
for_each_present_cpu ( cpu ) {
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
int cpustate = st - > state ;
if ( cpu > = failedcpu )
break ;
/* Did we invoke the startup call on that cpu ? */
if ( cpustate > = state )
cpuhp_issue_call ( cpu , state , teardown , false ) ;
}
}
/*
* Returns a free for dynamic slot assignment of the Online state . The states
* are protected by the cpuhp_slot_states mutex and an empty slot is identified
* by having no name assigned .
*/
static int cpuhp_reserve_state ( enum cpuhp_state state )
{
enum cpuhp_state i ;
mutex_lock ( & cpuhp_state_mutex ) ;
2016-02-26 21:43:39 +03:00
for ( i = CPUHP_AP_ONLINE_DYN ; i < = CPUHP_AP_ONLINE_DYN_END ; i + + ) {
if ( cpuhp_ap_states [ i ] . name )
2016-02-26 21:43:33 +03:00
continue ;
2016-02-26 21:43:39 +03:00
cpuhp_ap_states [ i ] . name = " Reserved " ;
2016-02-26 21:43:33 +03:00
mutex_unlock ( & cpuhp_state_mutex ) ;
return i ;
}
mutex_unlock ( & cpuhp_state_mutex ) ;
WARN ( 1 , " No more dynamic states available for CPU hotplug \n " ) ;
return - ENOSPC ;
}
/**
* __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
* @ state : The state to setup
* @ invoke : If true , the startup function is invoked for cpus where
* cpu state > = @ state
* @ startup : startup callback function
* @ teardown : teardown callback function
*
* Returns 0 if successful , otherwise a proper error code
*/
int __cpuhp_setup_state ( enum cpuhp_state state ,
const char * name , bool invoke ,
int ( * startup ) ( unsigned int cpu ) ,
int ( * teardown ) ( unsigned int cpu ) )
{
int cpu , ret = 0 ;
int dyn_state = 0 ;
if ( cpuhp_cb_check ( state ) | | ! name )
return - EINVAL ;
get_online_cpus ( ) ;
/* currently assignments for the ONLINE state are possible */
2016-02-26 21:43:39 +03:00
if ( state = = CPUHP_AP_ONLINE_DYN ) {
2016-02-26 21:43:33 +03:00
dyn_state = 1 ;
ret = cpuhp_reserve_state ( state ) ;
if ( ret < 0 )
goto out ;
state = ret ;
}
cpuhp_store_callbacks ( state , name , startup , teardown ) ;
if ( ! invoke | | ! startup )
goto out ;
/*
* Try to call the startup callback for each present cpu
* depending on the hotplug state of the cpu .
*/
for_each_present_cpu ( cpu ) {
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
int cpustate = st - > state ;
if ( cpustate < state )
continue ;
ret = cpuhp_issue_call ( cpu , state , startup , true ) ;
if ( ret ) {
cpuhp_rollback_install ( cpu , state , teardown ) ;
cpuhp_store_callbacks ( state , NULL , NULL , NULL ) ;
goto out ;
}
}
out :
put_online_cpus ( ) ;
if ( ! ret & & dyn_state )
return state ;
return ret ;
}
EXPORT_SYMBOL ( __cpuhp_setup_state ) ;
/**
* __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
* @ state : The state to remove
* @ invoke : If true , the teardown function is invoked for cpus where
* cpu state > = @ state
*
* The teardown callback is currently not allowed to fail . Think
* about module removal !
*/
void __cpuhp_remove_state ( enum cpuhp_state state , bool invoke )
{
int ( * teardown ) ( unsigned int cpu ) = cpuhp_get_teardown_cb ( state ) ;
int cpu ;
BUG_ON ( cpuhp_cb_check ( state ) ) ;
get_online_cpus ( ) ;
if ( ! invoke | | ! teardown )
goto remove ;
/*
* Call the teardown callback for each present cpu depending
* on the hotplug state of the cpu . This function is not
* allowed to fail currently !
*/
for_each_present_cpu ( cpu ) {
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , cpu ) ;
int cpustate = st - > state ;
if ( cpustate > = state )
cpuhp_issue_call ( cpu , state , teardown , false ) ;
}
remove :
cpuhp_store_callbacks ( state , NULL , NULL , NULL ) ;
put_online_cpus ( ) ;
}
EXPORT_SYMBOL ( __cpuhp_remove_state ) ;
2016-02-26 21:43:31 +03:00
# if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
static ssize_t show_cpuhp_state ( struct device * dev ,
struct device_attribute * attr , char * buf )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , dev - > id ) ;
return sprintf ( buf , " %d \n " , st - > state ) ;
}
static DEVICE_ATTR ( state , 0444 , show_cpuhp_state , NULL ) ;
2016-02-26 21:43:32 +03:00
static ssize_t write_cpuhp_target ( struct device * dev ,
struct device_attribute * attr ,
const char * buf , size_t count )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , dev - > id ) ;
struct cpuhp_step * sp ;
int target , ret ;
ret = kstrtoint ( buf , 10 , & target ) ;
if ( ret )
return ret ;
# ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
if ( target < CPUHP_OFFLINE | | target > CPUHP_ONLINE )
return - EINVAL ;
# else
if ( target ! = CPUHP_OFFLINE & & target ! = CPUHP_ONLINE )
return - EINVAL ;
# endif
ret = lock_device_hotplug_sysfs ( ) ;
if ( ret )
return ret ;
mutex_lock ( & cpuhp_state_mutex ) ;
sp = cpuhp_get_step ( target ) ;
ret = ! sp - > name | | sp - > cant_stop ? - EINVAL : 0 ;
mutex_unlock ( & cpuhp_state_mutex ) ;
if ( ret )
return ret ;
if ( st - > state < target )
ret = do_cpu_up ( dev - > id , target ) ;
else
ret = do_cpu_down ( dev - > id , target ) ;
unlock_device_hotplug ( ) ;
return ret ? ret : count ;
}
2016-02-26 21:43:31 +03:00
static ssize_t show_cpuhp_target ( struct device * dev ,
struct device_attribute * attr , char * buf )
{
struct cpuhp_cpu_state * st = per_cpu_ptr ( & cpuhp_state , dev - > id ) ;
return sprintf ( buf , " %d \n " , st - > target ) ;
}
2016-02-26 21:43:32 +03:00
static DEVICE_ATTR ( target , 0644 , show_cpuhp_target , write_cpuhp_target ) ;
2016-02-26 21:43:31 +03:00
static struct attribute * cpuhp_cpu_attrs [ ] = {
& dev_attr_state . attr ,
& dev_attr_target . attr ,
NULL
} ;
static struct attribute_group cpuhp_cpu_attr_group = {
. attrs = cpuhp_cpu_attrs ,
. name = " hotplug " ,
NULL
} ;
static ssize_t show_cpuhp_states ( struct device * dev ,
struct device_attribute * attr , char * buf )
{
ssize_t cur , res = 0 ;
int i ;
mutex_lock ( & cpuhp_state_mutex ) ;
2016-02-26 21:43:32 +03:00
for ( i = CPUHP_OFFLINE ; i < = CPUHP_ONLINE ; i + + ) {
2016-02-26 21:43:31 +03:00
struct cpuhp_step * sp = cpuhp_get_step ( i ) ;
if ( sp - > name ) {
cur = sprintf ( buf , " %3d: %s \n " , i , sp - > name ) ;
buf + = cur ;
res + = cur ;
}
}
mutex_unlock ( & cpuhp_state_mutex ) ;
return res ;
}
static DEVICE_ATTR ( states , 0444 , show_cpuhp_states , NULL ) ;
static struct attribute * cpuhp_cpu_root_attrs [ ] = {
& dev_attr_states . attr ,
NULL
} ;
static struct attribute_group cpuhp_cpu_root_attr_group = {
. attrs = cpuhp_cpu_root_attrs ,
. name = " hotplug " ,
NULL
} ;
static int __init cpuhp_sysfs_init ( void )
{
int cpu , ret ;
ret = sysfs_create_group ( & cpu_subsys . dev_root - > kobj ,
& cpuhp_cpu_root_attr_group ) ;
if ( ret )
return ret ;
for_each_possible_cpu ( cpu ) {
struct device * dev = get_cpu_device ( cpu ) ;
if ( ! dev )
continue ;
ret = sysfs_create_group ( & dev - > kobj , & cpuhp_cpu_attr_group ) ;
if ( ret )
return ret ;
}
return 0 ;
}
device_initcall ( cpuhp_sysfs_init ) ;
# endif
cpu masks: optimize and clean up cpumask_of_cpu()
Clean up and optimize cpumask_of_cpu(), by sharing all the zero words.
Instead of stupidly generating all possible i=0...NR_CPUS 2^i patterns
creating a huge array of constant bitmasks, realize that the zero words
can be shared.
In other words, on a 64-bit architecture, we only ever need 64 of these
arrays - with a different bit set in one single world (with enough zero
words around it so that we can create any bitmask by just offsetting in
that big array). And then we just put enough zeroes around it that we
can point every single cpumask to be one of those things.
So when we have 4k CPU's, instead of having 4k arrays (of 4k bits each,
with one bit set in each array - 2MB memory total), we have exactly 64
arrays instead, each 8k bits in size (64kB total).
And then we just point cpumask(n) to the right position (which we can
calculate dynamically). Once we have the right arrays, getting
"cpumask(n)" ends up being:
static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
{
const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
p -= cpu / BITS_PER_LONG;
return (const cpumask_t *)p;
}
This brings other advantages and simplifications as well:
- we are not wasting memory that is just filled with a single bit in
various different places
- we don't need all those games to re-create the arrays in some dense
format, because they're already going to be dense enough.
if we compile a kernel for up to 4k CPU's, "wasting" that 64kB of memory
is a non-issue (especially since by doing this "overlapping" trick we
probably get better cache behaviour anyway).
[ mingo@elte.hu:
Converted Linus's mails into a commit. See:
http://lkml.org/lkml/2008/7/27/156
http://lkml.org/lkml/2008/7/28/320
Also applied a family filter - which also has the side-effect of leaving
out the bits where Linus calls me an idio... Oh, never mind ;-)
]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 22:32:33 +04:00
/*
* cpu_bit_bitmap [ ] is a special , " compressed " data structure that
* represents all NR_CPUS bits binary values of 1 < < nr .
*
2009-01-01 02:42:28 +03:00
* It is used by cpumask_of ( ) to get a constant address to a CPU
cpu masks: optimize and clean up cpumask_of_cpu()
Clean up and optimize cpumask_of_cpu(), by sharing all the zero words.
Instead of stupidly generating all possible i=0...NR_CPUS 2^i patterns
creating a huge array of constant bitmasks, realize that the zero words
can be shared.
In other words, on a 64-bit architecture, we only ever need 64 of these
arrays - with a different bit set in one single world (with enough zero
words around it so that we can create any bitmask by just offsetting in
that big array). And then we just put enough zeroes around it that we
can point every single cpumask to be one of those things.
So when we have 4k CPU's, instead of having 4k arrays (of 4k bits each,
with one bit set in each array - 2MB memory total), we have exactly 64
arrays instead, each 8k bits in size (64kB total).
And then we just point cpumask(n) to the right position (which we can
calculate dynamically). Once we have the right arrays, getting
"cpumask(n)" ends up being:
static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
{
const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
p -= cpu / BITS_PER_LONG;
return (const cpumask_t *)p;
}
This brings other advantages and simplifications as well:
- we are not wasting memory that is just filled with a single bit in
various different places
- we don't need all those games to re-create the arrays in some dense
format, because they're already going to be dense enough.
if we compile a kernel for up to 4k CPU's, "wasting" that 64kB of memory
is a non-issue (especially since by doing this "overlapping" trick we
probably get better cache behaviour anyway).
[ mingo@elte.hu:
Converted Linus's mails into a commit. See:
http://lkml.org/lkml/2008/7/27/156
http://lkml.org/lkml/2008/7/28/320
Also applied a family filter - which also has the side-effect of leaving
out the bits where Linus calls me an idio... Oh, never mind ;-)
]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 22:32:33 +04:00
* mask value that has a single bit set only .
*/
2008-07-25 05:21:29 +04:00
cpu masks: optimize and clean up cpumask_of_cpu()
Clean up and optimize cpumask_of_cpu(), by sharing all the zero words.
Instead of stupidly generating all possible i=0...NR_CPUS 2^i patterns
creating a huge array of constant bitmasks, realize that the zero words
can be shared.
In other words, on a 64-bit architecture, we only ever need 64 of these
arrays - with a different bit set in one single world (with enough zero
words around it so that we can create any bitmask by just offsetting in
that big array). And then we just put enough zeroes around it that we
can point every single cpumask to be one of those things.
So when we have 4k CPU's, instead of having 4k arrays (of 4k bits each,
with one bit set in each array - 2MB memory total), we have exactly 64
arrays instead, each 8k bits in size (64kB total).
And then we just point cpumask(n) to the right position (which we can
calculate dynamically). Once we have the right arrays, getting
"cpumask(n)" ends up being:
static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
{
const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
p -= cpu / BITS_PER_LONG;
return (const cpumask_t *)p;
}
This brings other advantages and simplifications as well:
- we are not wasting memory that is just filled with a single bit in
various different places
- we don't need all those games to re-create the arrays in some dense
format, because they're already going to be dense enough.
if we compile a kernel for up to 4k CPU's, "wasting" that 64kB of memory
is a non-issue (especially since by doing this "overlapping" trick we
probably get better cache behaviour anyway).
[ mingo@elte.hu:
Converted Linus's mails into a commit. See:
http://lkml.org/lkml/2008/7/27/156
http://lkml.org/lkml/2008/7/28/320
Also applied a family filter - which also has the side-effect of leaving
out the bits where Linus calls me an idio... Oh, never mind ;-)
]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 22:32:33 +04:00
/* cpu_bit_bitmap[0] is empty - so we can back into it */
2011-03-23 02:34:07 +03:00
# define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
cpu masks: optimize and clean up cpumask_of_cpu()
Clean up and optimize cpumask_of_cpu(), by sharing all the zero words.
Instead of stupidly generating all possible i=0...NR_CPUS 2^i patterns
creating a huge array of constant bitmasks, realize that the zero words
can be shared.
In other words, on a 64-bit architecture, we only ever need 64 of these
arrays - with a different bit set in one single world (with enough zero
words around it so that we can create any bitmask by just offsetting in
that big array). And then we just put enough zeroes around it that we
can point every single cpumask to be one of those things.
So when we have 4k CPU's, instead of having 4k arrays (of 4k bits each,
with one bit set in each array - 2MB memory total), we have exactly 64
arrays instead, each 8k bits in size (64kB total).
And then we just point cpumask(n) to the right position (which we can
calculate dynamically). Once we have the right arrays, getting
"cpumask(n)" ends up being:
static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
{
const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
p -= cpu / BITS_PER_LONG;
return (const cpumask_t *)p;
}
This brings other advantages and simplifications as well:
- we are not wasting memory that is just filled with a single bit in
various different places
- we don't need all those games to re-create the arrays in some dense
format, because they're already going to be dense enough.
if we compile a kernel for up to 4k CPU's, "wasting" that 64kB of memory
is a non-issue (especially since by doing this "overlapping" trick we
probably get better cache behaviour anyway).
[ mingo@elte.hu:
Converted Linus's mails into a commit. See:
http://lkml.org/lkml/2008/7/27/156
http://lkml.org/lkml/2008/7/28/320
Also applied a family filter - which also has the side-effect of leaving
out the bits where Linus calls me an idio... Oh, never mind ;-)
]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 22:32:33 +04:00
# define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
# define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
# define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2008-07-25 05:21:29 +04:00
cpu masks: optimize and clean up cpumask_of_cpu()
Clean up and optimize cpumask_of_cpu(), by sharing all the zero words.
Instead of stupidly generating all possible i=0...NR_CPUS 2^i patterns
creating a huge array of constant bitmasks, realize that the zero words
can be shared.
In other words, on a 64-bit architecture, we only ever need 64 of these
arrays - with a different bit set in one single world (with enough zero
words around it so that we can create any bitmask by just offsetting in
that big array). And then we just put enough zeroes around it that we
can point every single cpumask to be one of those things.
So when we have 4k CPU's, instead of having 4k arrays (of 4k bits each,
with one bit set in each array - 2MB memory total), we have exactly 64
arrays instead, each 8k bits in size (64kB total).
And then we just point cpumask(n) to the right position (which we can
calculate dynamically). Once we have the right arrays, getting
"cpumask(n)" ends up being:
static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
{
const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
p -= cpu / BITS_PER_LONG;
return (const cpumask_t *)p;
}
This brings other advantages and simplifications as well:
- we are not wasting memory that is just filled with a single bit in
various different places
- we don't need all those games to re-create the arrays in some dense
format, because they're already going to be dense enough.
if we compile a kernel for up to 4k CPU's, "wasting" that 64kB of memory
is a non-issue (especially since by doing this "overlapping" trick we
probably get better cache behaviour anyway).
[ mingo@elte.hu:
Converted Linus's mails into a commit. See:
http://lkml.org/lkml/2008/7/27/156
http://lkml.org/lkml/2008/7/28/320
Also applied a family filter - which also has the side-effect of leaving
out the bits where Linus calls me an idio... Oh, never mind ;-)
]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 22:32:33 +04:00
const unsigned long cpu_bit_bitmap [ BITS_PER_LONG + 1 ] [ BITS_TO_LONGS ( NR_CPUS ) ] = {
MASK_DECLARE_8 ( 0 ) , MASK_DECLARE_8 ( 8 ) ,
MASK_DECLARE_8 ( 16 ) , MASK_DECLARE_8 ( 24 ) ,
# if BITS_PER_LONG > 32
MASK_DECLARE_8 ( 32 ) , MASK_DECLARE_8 ( 40 ) ,
MASK_DECLARE_8 ( 48 ) , MASK_DECLARE_8 ( 56 ) ,
2008-07-25 05:21:29 +04:00
# endif
} ;
cpu masks: optimize and clean up cpumask_of_cpu()
Clean up and optimize cpumask_of_cpu(), by sharing all the zero words.
Instead of stupidly generating all possible i=0...NR_CPUS 2^i patterns
creating a huge array of constant bitmasks, realize that the zero words
can be shared.
In other words, on a 64-bit architecture, we only ever need 64 of these
arrays - with a different bit set in one single world (with enough zero
words around it so that we can create any bitmask by just offsetting in
that big array). And then we just put enough zeroes around it that we
can point every single cpumask to be one of those things.
So when we have 4k CPU's, instead of having 4k arrays (of 4k bits each,
with one bit set in each array - 2MB memory total), we have exactly 64
arrays instead, each 8k bits in size (64kB total).
And then we just point cpumask(n) to the right position (which we can
calculate dynamically). Once we have the right arrays, getting
"cpumask(n)" ends up being:
static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
{
const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
p -= cpu / BITS_PER_LONG;
return (const cpumask_t *)p;
}
This brings other advantages and simplifications as well:
- we are not wasting memory that is just filled with a single bit in
various different places
- we don't need all those games to re-create the arrays in some dense
format, because they're already going to be dense enough.
if we compile a kernel for up to 4k CPU's, "wasting" that 64kB of memory
is a non-issue (especially since by doing this "overlapping" trick we
probably get better cache behaviour anyway).
[ mingo@elte.hu:
Converted Linus's mails into a commit. See:
http://lkml.org/lkml/2008/7/27/156
http://lkml.org/lkml/2008/7/28/320
Also applied a family filter - which also has the side-effect of leaving
out the bits where Linus calls me an idio... Oh, never mind ;-)
]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 22:32:33 +04:00
EXPORT_SYMBOL_GPL ( cpu_bit_bitmap ) ;
2008-11-05 05:39:10 +03:00
const DECLARE_BITMAP ( cpu_all_bits , NR_CPUS ) = CPU_BITS_ALL ;
EXPORT_SYMBOL ( cpu_all_bits ) ;
2008-12-30 01:35:14 +03:00
# ifdef CONFIG_INIT_ALL_POSSIBLE
2016-01-21 02:00:19 +03:00
struct cpumask __cpu_possible_mask __read_mostly
2016-01-21 02:00:16 +03:00
= { CPU_BITS_ALL } ;
2008-12-30 01:35:14 +03:00
# else
2016-01-21 02:00:19 +03:00
struct cpumask __cpu_possible_mask __read_mostly ;
2008-12-30 01:35:14 +03:00
# endif
2016-01-21 02:00:19 +03:00
EXPORT_SYMBOL ( __cpu_possible_mask ) ;
2008-12-30 01:35:14 +03:00
2016-01-21 02:00:19 +03:00
struct cpumask __cpu_online_mask __read_mostly ;
EXPORT_SYMBOL ( __cpu_online_mask ) ;
2008-12-30 01:35:14 +03:00
2016-01-21 02:00:19 +03:00
struct cpumask __cpu_present_mask __read_mostly ;
EXPORT_SYMBOL ( __cpu_present_mask ) ;
2008-12-30 01:35:14 +03:00
2016-01-21 02:00:19 +03:00
struct cpumask __cpu_active_mask __read_mostly ;
EXPORT_SYMBOL ( __cpu_active_mask ) ;
2008-12-30 01:35:16 +03:00
void init_cpu_present ( const struct cpumask * src )
{
2016-01-21 02:00:16 +03:00
cpumask_copy ( & __cpu_present_mask , src ) ;
2008-12-30 01:35:16 +03:00
}
void init_cpu_possible ( const struct cpumask * src )
{
2016-01-21 02:00:16 +03:00
cpumask_copy ( & __cpu_possible_mask , src ) ;
2008-12-30 01:35:16 +03:00
}
void init_cpu_online ( const struct cpumask * src )
{
2016-01-21 02:00:16 +03:00
cpumask_copy ( & __cpu_online_mask , src ) ;
2008-12-30 01:35:16 +03:00
}
2016-02-26 21:43:28 +03:00
/*
* Activate the first processor .
*/
void __init boot_cpu_init ( void )
{
int cpu = smp_processor_id ( ) ;
/* Mark the boot cpu "present", "online" etc for SMP and UP case */
set_cpu_online ( cpu , true ) ;
set_cpu_active ( cpu , true ) ;
set_cpu_present ( cpu , true ) ;
set_cpu_possible ( cpu , true ) ;
}
/*
* Must be called _AFTER_ setting up the per_cpu areas
*/
void __init boot_cpu_state_init ( void )
{
per_cpu_ptr ( & cpuhp_state , smp_processor_id ( ) ) - > state = CPUHP_ONLINE ;
}