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From: Eric Dumazet <edumazet@google.com>
To: paulmck@kernel.org
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-tip-commits@vger.kernel.org,
	syzbot <syzkaller@googlegroups.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>
Subject: Re: [tip: timers/core] hrtimer: Annotate lockless access to timer->state
Date: Thu, 7 Nov 2019 08:35:30 -0800	[thread overview]
Message-ID: <CANn89iLMD0=tiQ181qQ=qKo=Nom-XX4MqonZw6pKiYUzTDVjQg@mail.gmail.com> (raw)
In-Reply-To: <20191107161149.GQ20975@paulmck-ThinkPad-P72>

On Thu, Nov 7, 2019 at 8:11 AM Paul E. McKenney <paulmck@kernel.org> wrote:
>
> OK, so this is due to timer_pending() lockless access to ->entry.pprev
> to determine whether or not the timer is on the list.  New one on me!
>
> Given that use case, I don't have an objection to your patch to list.h.
>
> Except...
>
> Would it make sense to add a READ_ONCE() to hlist_unhashed()
> and to then make timer_pending() invoke hlist_unhashed()?  That
> would better confine the needed uses of READ_ONCE().

Sounds good to me, I had the same idea but was too lazy to look at the
history of timer_pending()
to check if the pprev pointer check was really the same underlying idea.

  reply	other threads:[~2019-11-07 16:35 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-06 17:48 [PATCH] hrtimer: Annotate lockless access to timer->state Eric Dumazet
2019-11-06 18:09 ` Thomas Gleixner
2019-11-06 18:19   ` Eric Dumazet
2019-11-06 19:15     ` Thomas Gleixner
2019-11-06 20:00       ` Eric Dumazet
2019-11-06 21:06 ` [tip: timers/core] " tip-bot2 for Eric Dumazet
2019-11-06 22:02   ` Eric Dumazet
2019-11-06 22:16     ` Thomas Gleixner
2019-11-06 22:24 ` tip-bot2 for Eric Dumazet
2019-11-06 22:53   ` Eric Dumazet
2019-11-06 22:59     ` Eric Dumazet
2019-11-07  8:52       ` Paul E. McKenney
2019-11-07 15:48         ` Eric Dumazet
2019-11-07 16:11           ` Paul E. McKenney
2019-11-07 16:35             ` Eric Dumazet [this message]
2019-11-07 16:39               ` Eric Dumazet
2019-11-07 16:54                 ` Paul E. McKenney
2019-11-07 16:59                   ` Eric Dumazet
2019-11-07 17:07                     ` Paul E. McKenney

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