Messages in this thread | | | Date | Fri, 3 Oct 2014 17:11:23 -0700 | Subject | Re: [tip:x86/asm] x86: Speed up ___preempt_schedule*() by using THUNK helpers | From | Linus Torvalds <> |
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On Fri, Oct 3, 2014 at 5:01 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > The real fix would appear to be to use > "preempt_enable_no_resched_notrace()", which your patch did, but > without the loop.
Actually, the real fix would be to not be stupid, and just make the code do something like
> if (likely(!preemptible())) > return; > > __preempt_count_add(PREEMPT_ACTIVE); > prev_ctx = exception_enter(); > > __schedule(); > > exception_exit(prev_ctx); > __preempt_count_sub(PREEMPT_ACTIVE);
and *not* enable preemption around the scheduling at all. The whole enable and then re-disable seems entirely broken, and comes from the code using "preempt_schedule()" which doesn't work while preemption is disabled. So don't do that then.
No?
Linus
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