summaryrefslogtreecommitdiffstats
path: root/kernel/sched.c
diff options
context:
space:
mode:
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-05-06 18:49:21 +0200
committerTejun Heo <tj@kernel.org>2010-05-06 18:49:21 +0200
commitcc631fb732b8ccd6a0cc45557475ea09b0c21a68 (patch)
tree37e8c84f227a21d628a9d3a96dbbf5fedd506db1 /kernel/sched.c
parent94458d5ecb3da844823cc191e73e5c5ead98a464 (diff)
downloadlinux-cc631fb732b8ccd6a0cc45557475ea09b0c21a68.tar.bz2
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: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c21
1 files changed, 11 insertions, 10 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index e9c6d798831a..155a16d52146 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);