Commit 81b047fa authored by Linus Torvalds's avatar Linus Torvalds Committed by sanglipeng1
Browse files

sched/membarrier: reduce the ability to hammer on sys_membarrier 

stable inclusion
from stable-v5.10.210
commit db896bbe4a9c67cee377e5f6a743350d3ae4acf6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAE52H

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=db896bbe4a9c67cee377e5f6a743350d3ae4acf6



--------------------------------

commit 944d5fe50f3f03daacfea16300e656a1691c4a23 upstream.

On some systems, sys_membarrier can be very expensive, causing overall
slowdowns for everything.  So put a lock on the path in order to
serialize the accesses to prevent the ability for this to be called at
too high of a frequency and saturate the machine.

Reviewed-and-tested-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: default avatarBorislav Petkov <bp@alien8.de>
Fixes: 22e4ebb9 ("membarrier: Provide expedited private command")
Fixes: c5f58bd5 ("membarrier: Provide GLOBAL_EXPEDITED command")
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
[ converted to explicit mutex_*() calls - cleanup.h is not in this stable
  branch - gregkh ]
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarsanglipeng1 <sanglipeng1@jd.com>
parent d3826ffe

kernel/sched/membarrier.c

+9 −0
Original line number Diff line number Diff line
@@ -34,6 +34,8 @@ 
	| MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK		\

	| MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK)



static DEFINE_MUTEX(membarrier_ipi_mutex);



static void ipi_mb(void *info)

{

	smp_mb();	/* IPIs should be serializing but paranoid. */
@@ -119,6 +121,7 @@ static int membarrier_global_expedited(void) 
	if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL))

		return -ENOMEM;



	mutex_lock(&membarrier_ipi_mutex);

	cpus_read_lock();

	rcu_read_lock();

	for_each_online_cpu(cpu) {
@@ -165,6 +168,8 @@ static int membarrier_global_expedited(void) 
	 * rq->curr modification in scheduler.

	 */

	smp_mb();	/* exit from system call is not a mb */

	mutex_unlock(&membarrier_ipi_mutex);



	return 0;

}
@@ -208,6 +213,7 @@ static int membarrier_private_expedited(int flags, int cpu_id) 
	if (cpu_id < 0 && !zalloc_cpumask_var(&tmpmask, GFP_KERNEL))

		return -ENOMEM;



	mutex_lock(&membarrier_ipi_mutex);

	cpus_read_lock();



	if (cpu_id >= 0) {
@@ -280,6 +286,7 @@ static int membarrier_private_expedited(int flags, int cpu_id) 
	 * rq->curr modification in scheduler.

	 */

	smp_mb();	/* exit from system call is not a mb */

	mutex_unlock(&membarrier_ipi_mutex);



	return 0;

}
@@ -321,6 +328,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm) 
	 * between threads which are users of @mm has its membarrier state

	 * updated.

	 */

	mutex_lock(&membarrier_ipi_mutex);

	cpus_read_lock();

	rcu_read_lock();

	for_each_online_cpu(cpu) {
@@ -337,6 +345,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm) 


	free_cpumask_var(tmpmask);

	cpus_read_unlock();

	mutex_unlock(&membarrier_ipi_mutex);



	return 0;

}