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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Sun, 5 Nov 2023 19:58:49 -0800
Message-ID: <CAM9d7ch9pXWZdFKf5zrQZg+nrf_0YpVro5vvkkO+LPfoLTynPQ@mail.gmail.com>
Subject: Re: [PATCH v4 01/53] perf comm: Use regular mutex
To:     Ian Rogers <irogers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Nick Terrell <terrelln@fb.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Vincent Whitchurch <vincent.whitchurch@axis.com>,
        "Steinar H. Gunderson" <sesse@google.com>,
        Liam Howlett <liam.howlett@oracle.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Colin Ian King <colin.i.king@gmail.com>,
        Dmitrii Dolgov <9erthalion6@gmail.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Ming Wang <wangming01@loongson.cn>,
        James Clark <james.clark@arm.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Leo Yan <leo.yan@linaro.org>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        German Gomez <german.gomez@arm.com>,
        Changbin Du <changbin.du@huawei.com>,
        Paolo Bonzini <pbonzini@redhat.com>, Li Dong <lidong@vivo.com>,
        Sandipan Das <sandipan.das@amd.com>,
        liuwenyu <liuwenyu7@huawei.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
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On Sun, Nov 5, 2023 at 1:35 PM Ian Rogers <irogers@google.com> wrote:
>
> On Sun, Nov 5, 2023 at 9:32 AM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > Hi Ian,
> >
> > On Thu, Nov 2, 2023 at 10:58 AM Ian Rogers <irogers@google.com> wrote:
> > >
> > > The rwsem is only after used for writing so switch to a mutex that has
> > > better error checking.
> >
> > Hmm.. ok.  It doesn't make sense to use rwsem without readers.
> >
> > >
> > > Fixes: 7a8f349e9d14 ("perf rwsem: Add debug mode that uses a mutex")
> >
> > But I'm not sure this is a fix.  Other than that,
>
> Thanks Namhyung, it fixes the case that you enable RWS_ERRORCHECK in
> rwsem.h as the rwsem static initialization is wrong for a mutex.

Sounds like we need a separate fix.  Maybe you need to
add a static initializer macro depending on the config.

Thanks,
Namhyung