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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Eric Dumazet <edumazet@google.com>, Will Deacon <will@kernel.org>
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: Confused about hlist_unhashed_lockless()
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References: <20200131164308.GA5175@willie-the-truck> <CANn89i+CnezK81gZSLOy0w7MaZy0uT=xyxoKSTyZU3aMpzifOA@mail.gmail.com> <20200131165718.GA5517@willie-the-truck> <CANn89iKmSBPKJGw--WaJJhCdu2wz2aq-ve+E8z=gfsYj6Zom_A@mail.gmail.com> <20200131172058.GB5517@willie-the-truck> <CANn89iJNgPOzCdc-7QoC+dawJVn7tLQxmrx58GL8PT9rDVT2hA@mail.gmail.com>
Date:   Fri, 31 Jan 2020 20:47:23 +0100
Message-ID: <87blqj4ddg.fsf@nanos.tec.linutronix.de>
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Eric Dumazet <edumazet@google.com> writes:
> On Fri, Jan 31, 2020 at 9:21 AM Will Deacon <will@kernel.org> wrote:
>> Without serialisation, timer_pending() as currently implemented does
>> not reliably tell you whether the timer is in the hlist. Is that not a
>> problem?
>
> No it is not a problem.

Even if we would take the base lock then this is just a snapshot, which
can be wrong at the moment the lock is dropped. So why bother?

Thanks,

        tglx