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Commit cc631fb7 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Tejun Heo
Browse files

sched: correctly place paranioa memory barriers in synchronize_sched_expedited() 



The memory barriers must be in the SMP case, not in the !SMP case.
Also add a barrier after the atomic_inc() in order to ensure that
other CPUs see post-synchronize_sched_expedited() actions as following
the expedited grace period.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 94458d5e

kernel/sched.c

+11 −10
Original line number Diff line number Diff line
@@ -8931,6 +8931,15 @@ struct cgroup_subsys cpuacct_subsys = { 
#ifndef CONFIG_SMP



void synchronize_sched_expedited(void)

{

}

EXPORT_SYMBOL_GPL(synchronize_sched_expedited);



#else /* #ifndef CONFIG_SMP */



static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0);



static int synchronize_sched_expedited_cpu_stop(void *data)

{

	/*

	 * There must be a full memory barrier on each affected CPU
@@ -8943,16 +8952,7 @@ void synchronize_sched_expedited(void) 
	 * necessary.  Do smp_mb() anyway for documentation and

	 * robustness against future implementation changes.

	 */

	smp_mb();

}

EXPORT_SYMBOL_GPL(synchronize_sched_expedited);



#else /* #ifndef CONFIG_SMP */



static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0);



static int synchronize_sched_expedited_cpu_stop(void *data)

{

	smp_mb(); /* See above comment block. */

	return 0;

}
@@ -8990,6 +8990,7 @@ void synchronize_sched_expedited(void) 
		get_online_cpus();

	}

	atomic_inc(&synchronize_sched_expedited_count);

	smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */

	put_online_cpus();

}

EXPORT_SYMBOL_GPL(synchronize_sched_expedited);