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sched/preempt: Fix up missed PREEMPT_NEED_RESCHED folding

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With various drivers wanting to inject idle time; we get people
calling idle routines outside of the idle loop proper.

Therefore we need to be extra careful about not missing
TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations.

While looking at this, I also realized there's a small window in the
existing idle loop where we can miss TIF_NEED_RESCHED; when it hits
right after the tif_need_resched() test at the end of the loop but
right before the need_resched() test at the start of the loop.

So move preempt_fold_need_resched() out of the loop where we're
guaranteed to have TIF_NEED_RESCHED set.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
2013-11-20 12:22:37 +01:00
committed by Ingo Molnar
parent c9c8986847
commit 8cb75e0c4e
5 changed files with 42 additions and 10 deletions
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2
arch/x86/include/asm/mwait.h
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@@ -53,7 +53,7 @@ static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
if (!need_resched())
__mwait(eax, ecx);
}
__current_clr_polling();
current_clr_polling();
}
#endif /* _ASM_X86_MWAIT_H */