linux-kernel - Re: [PATCH v3 09/18] perf ui: Update use of pthread mutex

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Date:   Fri, 26 Aug 2022 12:00:43 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Ian Rogers <irogers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Darren Hart <dvhart@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        André Almeida <andrealmeid@...lia.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Weiguo Li <liwg06@...mail.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
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        Remi Bernon <rbernon@...eweavers.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, llvm@...ts.linux.dev
Subject: Re: [PATCH v3 09/18] perf ui: Update use of pthread mutex

On Fri, Aug 26, 2022 at 11:53 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
> Below seems adequate for now, at least logically, but maybe it
> would confuse clang thread-safety analysis?

I think it's not just about locks, the exit_browser should bail out early
if the setup code was not called.

Thanks,
Namhyung


>
> diff --git a/tools/perf/ui/setup.c b/tools/perf/ui/setup.c
> index 25ded88801a3..6d81be6a349e 100644
> --- a/tools/perf/ui/setup.c
> +++ b/tools/perf/ui/setup.c
> @@ -73,9 +73,17 @@ int stdio__config_color(const struct option *opt __maybe_unused,
>         return 0;
>  }
>
> +/*
> + * exit_browser() can get called without setup_browser() having been called
> + * first, so it is necessary to keep track of whether ui__lock has been
> + * initialized.
> + */
> +static bool ui__lock_initialized;
> +
>  void setup_browser(bool fallback_to_pager)
>  {
>         mutex_init(&ui__lock);
> +       ui__lock_initialized = true;
>         if (use_browser < 2 && (!isatty(1) || dump_trace))
>                 use_browser = 0;
>
> @@ -118,5 +126,6 @@ void exit_browser(bool wait_for_ok)
>         default:
>                 break;
>         }
> -       mutex_destroy(&ui__lock);
> +       if (ui__lock_initialized)
> +               mutex_destroy(&ui__lock);
>  }
>