linux-kernel - Re: [PATCH] arm_pmu: Invert fallback armpmu

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Date:   Wed, 15 Feb 2023 11:42:33 +0000
From:   Eric Curtin <ecurtin@...hat.com>
To:     Janne Grunau <j@...nau.net>
Cc:     Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ravi Bangoria <ravi.bangoria@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev
Subject: Re: [PATCH] arm_pmu: Invert fallback armpmu_filter() return value

On Wed, 15 Feb 2023 at 11:40, Eric Curtin <ecurtin@...hat.com> wrote:
>
> On Wed, 15 Feb 2023 at 11:36, Janne Grunau <j@...nau.net> wrote:
> >
> > Fixes a regression in "perf: Rewrite core context handling" for arm_pmu
> > based drivers without a filter function pointer as the Apple M1 PMU.
> > The event is ignored if filter() returns 'true' opposite to
> > filter_match(). The refactoring failed to invert the return value if
> > arm_pmu has no filter() function pointer of its own.
> >
> > Fixes: bd2756811766 ("perf: Rewrite core context handling")
> > Signed-off-by: Janne Grunau <j@...nau.net>
>
> Makes sense we return the inverse of armpmu_filter everywhere else in the code.

or we return the inverse of cpumask_test_cpu rather... copy/paste
error on my part.

>
> Reviewed-by: Eric Curtin <ecurtin@...hat.com>
>
> Is mise le meas/Regards,
>
> Eric Curtin
>
> > ---
> >  drivers/perf/arm_pmu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> > index 9b593f985805..9cb22f36cf66 100644
> > --- a/drivers/perf/arm_pmu.c
> > +++ b/drivers/perf/arm_pmu.c
> > @@ -556,7 +556,7 @@ static bool armpmu_filter(struct pmu *pmu, int cpu)
> >         if (ret && armpmu->filter)
> >                 return armpmu->filter(pmu, cpu);
> >
> > -       return ret;
> > +       return !ret;
> >  }
> >
> >  static ssize_t cpus_show(struct device *dev,
> >
> > ---
> > base-commit: ceaa837f96adb69c0df0397937cd74991d5d821a
> > change-id: 20230215-arm_pmu_m1_regression-b6dd48d0c792
> >
> > Best regards,
> > --
> > Janne Grunau <j@...nau.net>
> >
> >