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authorPeter Zijlstra <peterz@infradead.org>2013-11-28 14:26:41 +0100
committerIngo Molnar <mingo@kernel.org>2013-12-11 15:52:32 +0100
commitba1f14fbe70965ae0fb1655a5275a62723f65b77 (patch)
tree412534b605bf33e5e930172686dd4f31d157fc51 /init
parent8e8339a3a1069141985daaa2521ba304509ddecd (diff)
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: Benjamin Herrenschmidt <benh@kernel.crashing.org> Reported-and-Tested-by: Alexander Graf <agraf@suse.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20131128132641.GP10022@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
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