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From:   Ian Rogers <irogers@google.com>
Date:   Mon, 24 Oct 2022 10:59:03 -0700
Message-ID: <CAP-5=fWPdmHPXc9D2LP6TVmhuNf93gZCnogWXCVGytkhuqi2uQ@mail.gmail.com>
Subject: Re: [PATCH v1 0/8] Update to C11, fix signal undefined behavior
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     Leo Yan <leo.yan@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>,
        German Gomez <german.gomez@arm.com>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        Stephane Eranian <eranian@google.com>
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On Mon, Oct 24, 2022 at 10:51 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Em Mon, Oct 24, 2022 at 10:35:15AM -0700, Ian Rogers escreveu:
> > The use of C11 is mainstream in the kernel [1]. There was some
> > confusion on volatile and signal handlers in [2]. Switch to using
> > stdatomic.h (requires C11) and sig_atomic_t as per [3]. Thanks to Leo
> > Yan <leo.yan@linaro.org> for the suggestions.
> >
> > [1] https://lore.kernel.org/lkml/CAHk-=whWbENRz-vLY6vpESDLj6kGUTKO3khGtVfipHqwewh2HQ@mail.gmail.com/
> > [2] https://lore.kernel.org/lkml/20221024011024.462518-1-irogers@google.com/
> > [3] https://wiki.sei.cmu.edu/confluence/display/c/SIG31-C.+Do+not+access+shared+objects+in+signal+handlers
>
> I think I'll apply this to perf/core, i.e. for 6.3, ok?

Sounds good to me. 6.3 or 6.2? I suspect there is more cleanup like
this and to the iterators (from C11) that can be done.

Thanks,
Ian

> - Arnaldo
>
> >
> > Ian Rogers (8):
> >   perf build: Update to C standard to gnu11
> >   perf record: Use sig_atomic_t for signal handlers
> >   perf daemon: Use sig_atomic_t to avoid UB
> >   perf ftrace: Use sig_atomic_t to avoid UB
> >   perf session: Change type to avoid UB
> >   perf stat: Use sig_atomic_t to avoid UB
> >   perf top: Use sig_atomic_t to avoid UB
> >   perf trace: Use sig_atomic_t to avoid UB
> >
> >  tools/perf/Makefile.config  | 2 +-
> >  tools/perf/builtin-daemon.c | 3 ++-
> >  tools/perf/builtin-ftrace.c | 4 ++--
> >  tools/perf/builtin-record.c | 9 +++++----
> >  tools/perf/builtin-stat.c   | 9 +++++----
> >  tools/perf/builtin-top.c    | 4 ++--
> >  tools/perf/builtin-trace.c  | 4 ++--
> >  tools/perf/util/session.c   | 3 ++-
> >  8 files changed, 21 insertions(+), 17 deletions(-)
> >
> > --
> > 2.38.0.135.g90850a2211-goog
>
> --
>
> - Arnaldo