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

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Message-ID: <1263890793.4283.639.camel@laptop>
Date:	Tue, 19 Jan 2010 09:46:33 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
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()

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

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