linux-kernel - Re: [PATCH] perf test: Remove atomics from test

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Date:   Tue, 21 Nov 2023 14:04:26 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     James Clark <james.clark@....com>
Cc:     Nick Forrington <nick.forrington@....com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH] perf test: Remove atomics from test_loop to avoid test
 failures

Em Fri, Nov 03, 2023 at 09:14:45AM +0000, James Clark escreveu:
> On 02/11/2023 16:22, Nick Forrington wrote:
> > The current use of atomics can lead to test failures, as tests (such as
> > tests/shell/record.sh) search for samples with "test_loop" as the
> > top-most stack frame, but find frames related to the atomic operation
> > (e.g. __aarch64_ldadd4_relax).

> > This change simply removes the "count" variable, as it is not necessary.

> > Fixes: 1962ab6f6e0b ("perf test workload thloop: Make count increments atomic")
> > Signed-off-by: Nick Forrington <nick.forrington@....com>

> > +++ b/tools/perf/tests/workloads/thloop.c
> > @@ -7,7 +7,6 @@
> >   #include "../tests.h"
> >   static volatile sig_atomic_t done;
> > -static volatile unsigned count;
> >   /* We want to check this symbol in perf report */
> >   noinline void test_loop(void);
> > @@ -19,8 +18,7 @@ static void sighandler(int sig __maybe_unused)
> >   noinline void test_loop(void)
> >   {
> > -	while (!done)
> > -		__atomic_fetch_add(&count, 1, __ATOMIC_RELAXED);
> > +	while (!done);
> >   }
> >   static void *thfunc(void *arg)
 
> Reviewed-by: James Clark <james.clark@....com>

Thanks, applied to perf-tools-next.

- Arnaldo