linux-kernel - Re: [PATCH] perf: cs-etm: Fix the assert() to handle captured and unprocessed cpu trace

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Message-ID: <ZvSXFx4N2vXReqZs@google.com>
Date: Wed, 25 Sep 2024 16:04:55 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: James Clark <james.clark@...aro.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Ilkka Koskinen <ilkka@...amperecomputing.com>,
	linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
	Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH] perf: cs-etm: Fix the assert() to handle captured and
 unprocessed cpu trace

On Wed, Sep 25, 2024 at 10:54:31AM +0100, James Clark wrote:
> 
> 
> On 25/09/2024 12:39 am, Ilkka Koskinen wrote:
> > If one builds perf with DEBUG=1, captures data on multiple CPUs and
> > finally runs 'perf report -C <cpu>' for only one of the cpus, assert()
> > aborts the program. This happens because there are empty queues with
> > format set. This patch changes the condition to abort only if a queue
> > is not empty and if the format is unset.
> > 
> >    $ make -C tools/perf DEBUG=1 CORESIGHT=1 CSLIBS=/usr/lib CSINCLUDES=/usr/include install
> >    $ perf record -o kcore --kcore -e cs_etm/timestamp/k -s -C 0-1 dd if=/dev/zero of=/dev/null bs=1M count=1
> >    $ perf report --input kcore/data --vmlinux=/home/ikoskine/projects/linux/vmlinux -C 1
> >    Aborted (core dumped)
> > 
> > Fixes: 57880a7966be ("perf: cs-etm: Allocate queues for all CPUs")
> > Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
> > ---
> >   tools/perf/util/cs-etm.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> > index 90f32f327b9b..40f047baef81 100644
> > --- a/tools/perf/util/cs-etm.c
> > +++ b/tools/perf/util/cs-etm.c
> > @@ -3323,7 +3323,7 @@ static int cs_etm__create_decoders(struct cs_etm_auxtrace *etm)
> >   		 * Don't create decoders for empty queues, mainly because
> >   		 * etmq->format is unknown for empty queues.
> >   		 */
> > -		assert(empty == (etmq->format == UNSET));
> > +		assert(empty || etmq->format != UNSET);
> >   		if (empty)
> >   			continue;
> 
> Oops I didn't realize you could filter on CPU in report mode. Thanks for the
> fix. Adding a test to the end of test_arm_coresight.sh might be quite
> useful. Either way:
> 
> Reviewed-by: James Clark <james.clark@...aro.org>
 
Thanks, it should go to the perf-tool.  Arnaldo, please pick up.
Namhyung