linux-kernel - Re: [PATCH v1 0/8] Update to C11, fix signal undefined behavior

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Message-ID: <CAP-5=fVGicObnifnUzDXjbkGOVtmNaLKcfqpGeTwnFw2zsOuDQ@mail.gmail.com>
Date:   Mon, 24 Oct 2022 11:11:49 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Leo Yan <leo.yan@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        German Gomez <german.gomez@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v1 0/8] Update to C11, fix signal undefined behavior

On Mon, Oct 24, 2022 at 10:59 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Mon, Oct 24, 2022 at 10:51 AM Arnaldo Carvalho de Melo
> <acme@...nel.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@...aro.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

So I noticed a few changes missing #include-ing stdatomic.h and
sig_atomic_t is actually in signal.h. I'm not sure we need the C11
change then, but it seems like the right thing to do anyway. I'll do a
v2 to drop the unneeded (currently) include of stdatomic.h.

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