linux-kernel - Re: [PATCH v2 2/3] perf unwind: fix libunwind when tid != pid

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Message-ID: <20190816153046.GA22547@kernel.org>
Date:   Fri, 16 Aug 2019 12:30:46 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     John Keeping <john@...anate.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] perf unwind: fix libunwind when tid != pid

Em Thu, Aug 15, 2019 at 04:10:35PM +0200, Jiri Olsa escreveu:
> On Thu, Aug 15, 2019 at 11:01:45AM +0100, John Keeping wrote:
> > Commit e5adfc3e7e77 ("perf map: Synthesize maps only for thread group
> > leader") changed the recording side so that we no longer get mmap events
> > for threads other than the thread group leader (when synthesising these
> > events for threads which exist before perf is started).
> > 
> > When a file recorded after this change is loaded, the lack of mmap
> > records mean that unwinding is not set up for any other threads.
> > 
> > This can be seen in a simple record/report scenario:
> > 
> > 	perf record --call-graph=dwarf -t $TID
> > 	perf report
> > 
> > If $TID is a process ID then the report will show call graphs, but if
> > $TID is a secondary thread the output is as if --call-graph=none was
> > specified.
> 
> great, mucch clearler now
> 
> > 
> > Following the rationale in that commit, move the libunwind fields into
> > struct map_groups and update the libunwind functions to take this
> > instead of the struct thread.  This is only required for
> > unwind__finish_access which must now be called from map_groups__delete
> > and the others are changed for symmetry.
> > 
> > Note that unwind__get_entries keeps the thread argument since it is
> > required for symbol lookup and the libdw unwind provider uses the thread
> > ID.
> > 
> > Fixes: e5adfc3e7e77 ("perf map: Synthesize maps only for thread group leader")
> 
> for all 3 patches
> 
> Reviewed-by: Jiri Olsa <jolsa@...nel.org>


Thanks, applied.

- Arnaldo