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Message-ID: <53EAFCED.8030206@intel.com>
Date: Wed, 13 Aug 2014 08:51:41 +0300
From: Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
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To: Namhyung Kim <namhyung@gmail.com>
CC: Arnaldo Carvalho de Melo <acme@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Paul Mackerras <paulus@samba.org>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 3/4] perf tools: Fix probing the kernel API with cpu-wide
 events
References: <1407855871-15024-1-git-send-email-adrian.hunter@intel.com>	<1407855871-15024-4-git-send-email-adrian.hunter@intel.com> <87egwldk5m.fsf@sejong.aot.lge.com>
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On 08/13/2014 08:37 AM, Namhyung Kim wrote:
> On Tue, 12 Aug 2014 18:04:30 +0300, Adrian Hunter wrote:
>> Fall back to probing with the current pid if cpu-wide
>> probing fails.  This primarily affects the setting of
>> comm_exec flag when the user is un-privileged and
>> /proc/sys/kernel/perf_event_paranoid > 0.  The change
>> to comm_exec can be observed by using -vv with
>> perf record and a kernel that supports comm_exec.
> 
> Maybe I'm missing something - why not just try process-wide probing in
> the first place?

Same reason as patch 4 i.e. to avoid a jump label change when doing
system-wide tracing.