linux-kernel - Re: [RFC PATCH v1] perf parse-events: Make legacy events lower priority than sysfs/json

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Date:   Thu, 23 Nov 2023 18:15:09 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Hector Martin <marcan@...can.st>
Cc:     Mark Rutland <mark.rutland@....com>,
        Ian Rogers <irogers@...gle.com>, Marc Zyngier <maz@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1] perf parse-events: Make legacy events lower
 priority than sysfs/json

Em Thu, Nov 23, 2023 at 11:18:22AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Nov 23, 2023 at 05:45:19PM +0900, Hector Martin escreveu:
> > On 2023/11/23 13:29, Ian Rogers wrote:
> > > The bulk of this change is updating all of the parse-events test
> > > expectations so that if a sysfs/json event exists for a PMU the test
> > > doesn't fail - a further sign, if it were needed, that the legacy
> > > event priority was a known and tested behavior of the perf tool.
> 
> > > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > > ---
> > > This is a large behavioral change:
> > > 1) the scope of the change means it should bake on linux-next and I
> > > don't believe should be a 6.7-rc fix.
> > > 2) a fixes tag and stable backport I don't think are appropriate. The
> > > real reported issue is with the PMU driver. A backport would bring the
> > > risk that later fixes, due to the large behavior change, wouldn't be
> > > backported and past releases get regressed in scenarios like
> > > hybrid. Backports for the perf tool are also less necessary than say a
> > > buggy PMU driver, as distributions should be updating to the latest
> > > perf tool regardless of what Linux kernel is being run (the perf tool
> > > is backward compatible).
> > 
> > Tested-by: Hector Martin <marcan@...can.st>
> 
> Thanks, applied locally, doing some tests and then will push for
> linux-next to pick it up.
> 
> Mark, can I have your Reviewed-by or Acked-by?

I'll collect those, but only after addressing these:

[perfbuilder@...e ~]$ export BUILD_TARBALL=http://192.168.86.5/perf/perf-6.6.0-rc1.tar.xz
[perfbuilder@...e ~]$ time dm
   1   100.09 almalinux:8                   : FAIL clang version 15.0.7 (Red Hat 15.0.7-1.module_el8.8.0+3466+dfcbc058)
    util/parse-events.c:1461:6: error: variable 'alias_rewrote_terms' is used uninitialized whenever '&&' condition is false [-Werror,-Wsometimes-uninitialized]
            if (!parse_state->fake_pmu && perf_pmu__check_alias(pmu, &parsed_terms,
                ^~~~~~~~~~~~~~~~~~~~~~
    util/parse-events.c:1477:6: note: uninitialized use occurs here
            if (alias_rewrote_terms &&
                ^~~~~~~~~~~~~~~~~~~
    util/parse-events.c:1461:6: note: remove the '&&' if its condition is always true
            if (!parse_state->fake_pmu && perf_pmu__check_alias(pmu, &parsed_terms,
                ^~~~~~~~~~~~~~~~~~~~~~~~~
    util/parse-events.c:1401:26: note: initialize the variable 'alias_rewrote_terms' to silence this warning
            bool alias_rewrote_terms;
                                    ^
                                     = false
    1 error generated.
    make[3]: *** [/git/perf-6.6.0-rc1/tools/build/Makefile.build:158: util] Error 2
   2   114.29 almalinux:9                   : FAIL clang version 15.0.7 (Red Hat 15.0.7-2.el9)
    util/parse-events.c:1461:6: error: variable 'alias_rewrote_terms' is used uninitialized whenever '&&' condition is false [-Werror,-Wsometimes-uninitialized]
            if (!parse_state->fake_pmu && perf_pmu__check_alias(pmu, &parsed_terms,
                ^~~~~~~~~~~~~~~~~~~~~~
    util/parse-events.c:1477:6: note: uninitialized use occurs here
            if (alias_rewrote_terms &&
                ^~~~~~~~~~~~~~~~~~~
    util/parse-events.c:1461:6: note: remove the '&&' if its condition is always true
            if (!parse_state->fake_pmu && perf_pmu__check_alias(pmu, &parsed_terms,
                ^~~~~~~~~~~~~~~~~~~~~~~~~
    util/parse-events.c:1401:26: note: initialize the variable 'alias_rewrote_terms' to silence this warning
            bool alias_rewrote_terms;
                                    ^
                                     = false
    1 error generated.
    make[3]: *** [/git/perf-6.6.0-rc1/tools/build/Makefile.build:158: util] Error 2