Author: kib
Date: Fri Jul 10 08:54:12 2015
New Revision: 285353
URL: https://svnweb.freebsd.org/changeset/base/285353
Log:
Change the mb() use in the sched_ult tdq_notify() and sched_idletd()
to more C11-ish atomic_thread_fence_seq_cst().
Note that on PowerPC, which currently uses lwsync for mb(), the change
actually fixes the missed store/load barrier, intended by r271604 [*].
Reviewed by: alc
Noted by: alc [*]
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks
Modified:
head/sys/kern/sched_ule.c
Modified: head/sys/kern/sched_ule.c
==============================================================================
--- head/sys/kern/sched_ule.c Fri Jul 10 08:36:22 2015 (r285352)
+++ head/sys/kern/sched_ule.c Fri Jul 10 08:54:12 2015 (r285353)
@@ -1057,7 +1057,7 @@ tdq_notify(struct tdq *tdq, struct threa
* globally visible before we read tdq_cpu_idle. Idle thread
* accesses both of them without locks, and the order is important.
*/
- mb();
+ atomic_thread_fence_seq_cst();
if (TD_IS_IDLETHREAD(ctd)) {
/*
@@ -2667,7 +2667,7 @@ sched_idletd(void *dummy)
* before cpu_idle() read tdq_load. The order is important
* to avoid race with tdq_notify.
*/
- mb();
+ atomic_thread_fence_seq_cst();
cpu_idle(switchcnt * 4 > sched_idlespinthresh);
tdq->tdq_cpu_idle = 0;
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