Messages in this thread |  | | Date | Thu, 28 Nov 2013 16:24:45 +0100 | From | Alexander Graf <> | Subject | Re: [PATCH] sched: Remove PREEMPT_NEED_RESCHED from generic code |
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On 11/28/2013 02:26 PM, Peter Zijlstra wrote: > Subject: sched: Remove PREEMPT_NEED_RESCHED from generic code > > While hunting a preemption issue with Alexander, Ben noticed that the > currently generic PREEMPT_NEED_RESCHED stuff is horribly broken for > load-store architectures. > > We currently rely on the IPI to fold TIF_NEED_RESCHED into > PREEMPT_NEED_RESCHED, but when this IPI lands while we already have > a load for the preempt-count but before the store, the store will erase > the PREEMPT_NEED_RESCHED change. > > The current preempt-count only works on load-store archs because > interrupts are assumed to be completely balanced wrt their preempt_count > fiddling; the previous preempt_count load will match the preempt_count > state after the interrupt and therefore nothing gets lost. > > This patch removes the PREEMPT_NEED_RESCHED usage from generic code and > pushes it into x86 arch code; the generic code goes back to relying on > TIF_NEED_RESCHED. > > Boot tested on x86_64 and compile tested on ppc64. > > Reported-by: Alexander Graf <agraf@suse.de> > Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Fixes the issue for me.
Tested-by: Alexander Graf <agraf@suse.de>
Alex
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