linux-kernel - Re: [PATCH] perf: Don't show unwind error messages when augmenting frame pointer stack

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Message-ID: <YlGhI1nHOpbb09GU@kernel.org>
Date:   Sat, 9 Apr 2022 12:07:15 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, alexandre.truong@....com,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        German Gomez <german.gomez@....com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: Don't show unwind error messages when augmenting
 frame pointer stack

Em Fri, Apr 08, 2022 at 03:12:15PM +0100, John Garry escreveu:
> On 06/04/2022 15:56, James Clark wrote:
> > Commit b9f6fbb3b2c2 ("perf arm64: Inject missing frames when using 'perf
> > record --call-graph=fp'") intended to add a 'best effort' Dwarf unwind
> > that improved the frame pointer stack in most scenarios. It's expected
> > that the unwind will fail sometimes, but this shouldn't be reported as
> > an error. It only works when the return address can be determined from
> > the contents of the link register alone.
> > 
> > Fix the error shown when the unwinder requires extra registers by adding
> > a new flag that suppresses error messages. This flag is not set in the
> > normal --call-graph=dwarf unwind mode so that behavior is not changed.
> > 
> > Reported-by: John Garry <john.garry@...wei.com>
> > Fixes: b9f6fbb3b2c2 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'")
> > Signed-off-by: James Clark <james.clark@....com>
> 
> Seems ok:
> Tested-by: John Garry <john.garry@...wei.com>

Thanks, applied.

- Arnaldo