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From:   Thomas Gleixner <tglx@linutronix.de>
To:     paulmck@kernel.org, Marco Elver <elver@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Ingo Molnar <mingo@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Will Deacon <will@kernel.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
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        syzbot+56078ac0b9071335a745@syzkaller.appspotmail.com,
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Subject: Re: [patch 3/3] tick: Annotate tick_do_timer_cpu data races
In-Reply-To: <20201207194406.GK2657@paulmck-ThinkPad-P72>
References: <20201206211253.919834182@linutronix.de> <20201206212002.876987748@linutronix.de> <20201207120943.GS3021@hirez.programming.kicks-ass.net> <87y2i94igo.fsf@nanos.tec.linutronix.de> <CANpmjNNQiTbnkkj+ZHS5xxQuQfnWN_JGwSnN-_xqfa=raVrXHQ@mail.gmail.com> <20201207194406.GK2657@paulmck-ThinkPad-P72>
Date:   Mon, 07 Dec 2020 22:46:33 +0100
Message-ID: <87blf547d2.fsf@nanos.tec.linutronix.de>
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On Mon, Dec 07 2020 at 11:44, Paul E. McKenney wrote:
> On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote:
>> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner <tglx@linutronix.de> wrote:
>> I currently don't know what the rule for Peter's preferred variant
>> would be, without running the risk of some accidentally data_race()'d
>> accesses.
>> 
>> Thoughts?
>
> I am also concerned about inadvertently covering code with data_race().
>
> Also, in this particular case, why data_race() rather than READ_ONCE()?
> Do we really expect the compiler to be able to optimize this case
> significantly without READ_ONCE()?

That was your suggestion a week or so ago :)

Thanks,

        tglx