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

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Message-ID: <20140728081948.GA1124@krava.brq.redhat.com>
Date:	Mon, 28 Jul 2014 10:19:48 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.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 Mon, Jul 28, 2014 at 08:58:44AM +0200, Peter Zijlstra wrote:
> 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.

right, it would.. Ingo, still any chance to skip this one?

[jolsa@...p-26-214 perf]$ ./perf record sleep 1
perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 13 (Permission denied)
perf_event_open(..., 0) failed unexpectedly with error 13 (Permission denied)

jirka
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