linux-kernel - Re: [PATCH 02/27] perf tools: Fix jump label always changing during tracing

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Message-ID: <20140728065844.GK6758@twins.programming.kicks-ass.net>
Date:	Mon, 28 Jul 2014 08:58:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 02/27] perf tools: Fix jump label always changing during
 tracing

On Fri, Jul 25, 2014 at 12:36:44PM -0300, Arnaldo Carvalho de Melo wrote:
> From: Adrian Hunter <adrian.hunter@...el.com>
> 
> Intel PT decoding walks the object code to reconstruct the trace.  A
> jump label change during tracing causes decoding errors.
> 
> The "Enable close-on-exec flag on perf file descriptor" patch caused
> there to be always a jump label change.
> 
> It was found that using a per-cpu context instead of a per-thread
> context for the probe of the close-on-exec feature, made the problem go
> away.

per-cpu events are privileged, wouldn't this change make CLOEXEC always
undetected for normal users?

Also, the $subject doesn't related to CLOEXEC at all.

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