linux-kernel - Re: [PATCH 1/3 v2] perf_event: fix race in perf_swevent_get_recursion

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Message-ID: <4B55762F.7010204@cn.fujitsu.com>
Date:	Tue, 19 Jan 2010 17:06:55 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Jason Baron <jbaron@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3 v2] perf_event: fix race in perf_swevent_get_recursion_context()



Peter Zijlstra wrote:
> On Tue, 2010-01-19 at 16:37 +0800, Xiao Guangrong wrote:
>> It only disable preemption in perf_swevent_get_recursion_context(),
>> it can't avoid race of hard-irq and NMI since they are nested that
>> will re-enter this path and make the recursion value chaotic
>>
>> In this patch, we use atomic operation to avoid it and reduce
>> cpu_ctx->recursion size, it also make this patch no need disable
>> preemption
> 
> NAK
> 

Sorry, i forget the nesting of hard-irq is sequential, and not pollute
recursion value, thanks for you point out.

Hi Ingo,

Please ignore this patch, it not pollute other 2 patches in this
patchset

Thanks,
Xiao
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