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
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=285353
@ -1057,7 +1057,7 @@ tdq_notify(struct tdq *tdq, struct thread *td)
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* globally visible before we read tdq_cpu_idle. Idle thread
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* accesses both of them without locks, and the order is important.
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*/
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mb();
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atomic_thread_fence_seq_cst();
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if (TD_IS_IDLETHREAD(ctd)) {
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/*
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@ -2667,7 +2667,7 @@ sched_idletd(void *dummy)
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* before cpu_idle() read tdq_load. The order is important
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* to avoid race with tdq_notify.
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*/
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mb();
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atomic_thread_fence_seq_cst();
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cpu_idle(switchcnt * 4 > sched_idlespinthresh);
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tdq->tdq_cpu_idle = 0;
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