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From:   Ian Rogers <irogers@google.com>
Date:   Fri, 26 Aug 2022 13:52:07 -0700
Message-ID: <CAP-5=fWvf66snfmUfaTQ6BZ9EmsmBs0PUT8PAfehW74bnEE5nQ@mail.gmail.com>
Subject: Re: [PATCH v3 09/18] perf ui: Update use of pthread mutex
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Adrian Hunter <adrian.hunter@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
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On Fri, Aug 26, 2022 at 1:40 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Fri, Aug 26, 2022 at 12:21 PM Adrian Hunter <adrian.hunter@intel.com> wrote:
> >
> > On 26/08/22 22:00, Namhyung Kim wrote:
> > > On Fri, Aug 26, 2022 at 11:53 AM Adrian Hunter <adrian.hunter@intel.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.
> >
> > In those cases, use_browser is 0 or -1 unless someone has inserted
> > an invalid perf config like "tui.script=on" or "gtk.script=on".
> > So currently, in cases where exit_browser() is called without
> > setup_browser(), it does nothing.  Which means it is only the
> > unconditional mutex_destroy() that needs to be conditional.
>
> Yeah there's a possibility that it can be called with > 0 use_browser
> on some broken config or something.  So I think it's safer and better
> for future changes.

I'd thought about a:
static bool ui__lock_initialized;
but the issue is shouldn't it be atomic? Maybe we should guard it with
a lock? Then we are back where we started. Having a clean init/exit
invariant would be best but such a change has the potential to be
large and out of scope here.

Thanks,
Ian

> Thanks,
> Namhyung