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Date: Fri, 5 Apr 2013 09:57:13 +0530 From: Vineet Gupta <Vineet.Gupta1@...opsys.com> To: Peter Zijlstra <peterz@...radead.org> CC: Christian Ruppert <christian.ruppert@...lis.com>, Thomas Gleixner <tglx@...utronix.de>, Pierrick Hascoet <pierrick.hascoet@...lis.com>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org> Subject: Re: [RFC] Add implicit barriers to irqsave/restore class of functions Hi Peter, On 04/04/2013 09:43 PM, Peter Zijlstra wrote: > - : "cc"); > + : "memory", "cc"); > That's not a memory barrier, that a memory clobber, aka a compiler > barrier. For the problem under consideration we indeed want a compiler barrier because the error shows up due to a stale register which is live across a spinlock for !PREEMPT_COUNT config. However IMO doing this in irq save/restore macros is semantically incorrect since those macros might be used elsewhere which don't need the compiler reload reg semantics. Further per tglx' suggestion fixing preempt_* macros for !PREEMPT_COUNT case would fix this independent of what arch is doing. A patch to that effect was already posted to lists: http://www.spinics.net/lists/kernel/msg1510885.html Please let us know what you think. Thx, -Vineet -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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