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Date: Thu, 3 Dec 2015 22:28:33 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
        Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 1/2] x86, perf: Remove warning for zero PEBS status
Message-ID: <20151203212833.GA17308@twins.programming.kicks-ass.net>
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On Thu, Dec 03, 2015 at 01:22:19PM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> 
> The recent change 75f80859b1 (... Robustify PEBS buffer drain)
> causes lots of warnings on different CPUs before Skylake
> when running PEBS intensive workloads.
> 
> They can have a zero status field in the PEBS record when
> PEBS is racing with clearing of GLOBAl_STATUS.

Ah, so _that_ is the explanation! Please put that in a comment near that
code. This has long puzzled me.

Thanks for digging into that.