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

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Message-ID: <5160d57a-3520-4d99-ae10-5cc539fba813@linaro.org>
Date: Wed, 25 Sep 2024 10:54:31 +0100
From: James Clark <james.clark@...aro.org>
To: Ilkka Koskinen <ilkka@...amperecomputing.com>
Cc: 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>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, 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 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>