linux-kernel - Re: [PATCH] perf tools: fix processing of pid/tid for mmap records

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Message-ID: <20140422133242.GF1104@krava.brq.redhat.com>
Date:	Tue, 22 Apr 2014 15:32:43 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, acme@...hat.com,
	peterz@...radead.org, mingo@...e.hu, namhyung@...nel.org,
	dsahern@...il.com
Subject: Re: [PATCH] perf tools: fix processing of pid/tid for mmap records

hi,

On Mon, Apr 21, 2014 at 06:06:55PM +0200, Stephane Eranian wrote:
> perf tools: fix processing of pid/tid for mmap records

extra description line ^^^

>     
> Mmaps are global to a process (always). Processing them
> per-thread was causing some serious issues in case mmaps
> would overlap. The overlap fixups would only occur in the
> context of the thread which generated the overlapping
> mmap. But that was cause issues later on when a sample
> from another thread would fall into that overlapping
> mmap.
> 
> The solution to the problem is to handle ALL mmaps as
> occurring in the master thread (pid = tid) and then to
> lookup for thread map using pid as the tid argument.
> This is how samples are looking up for the thread map
> already (notice pid passed twice):
>     
> int perf_event__preprocess_sample(const union perf_event *event,
>                                   struct machine *machine,
>                                   struct addr_location *al,
>                                   struct perf_sample *sample)
> {
>         struct thread *thread = machine__findnew_thread(machine, sample->pid,
>                                                         sample->pid);
> }
>     
> Without this fix, some samples in overlapping regions
> may not be symbolized.

could you please take a look on following patchset:
http://marc.info/?l=linux-kernel&m=139749074531132&w=2

this makes the map groups shared within the process,
so it should fix above issue as well

thanks,
jirka
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