Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 5/5] sched: correctly place paranioa memory barriers in synchronize_sched_expedited() | Date | Thu, 6 May 2010 18:52:52 +0200 |
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From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org> --- kernel/sched.c | 21 +++++++++++---------- 1 files changed, 11 insertions(+), 10 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c index e9c6d79..155a16d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -8932,6 +8932,15 @@ struct cgroup_subsys cpuacct_subsys = { 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 * between the time that try_stop_cpus() is called and the @@ -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); -- 1.6.4.2
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