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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Marco Elver <elver@google.com>,
	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>,
	syzbot+23a256029191772c2f02@syzkaller.appspotmail.com,
	syzbot+56078ac0b9071335a745@syzkaller.appspotmail.com,
	syzbot+867130cb240c41f15164@syzkaller.appspotmail.com
Subject: Re: [patch 3/3] tick: Annotate tick_do_timer_cpu data races
Date: Wed, 16 Dec 2020 13:32:18 -0800	[thread overview]
Message-ID: <20201216213218.GM2657@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <87czz9savm.fsf@nanos.tec.linutronix.de>

On Wed, Dec 16, 2020 at 10:23:57PM +0100, Thomas Gleixner wrote:
> On Wed, Dec 16 2020 at 13:19, Paul E. McKenney wrote:
> > On Wed, Dec 16, 2020 at 01:27:43AM +0100, Thomas Gleixner wrote:
> >> So my intent was to document that this code does not care about anything
> >> else than what I'd consider to be plain compiler bugs.
> >> 
> >> My conclusion might be wrong as usual :)
> >
> > Given that there is no optimization potential, then the main reason to use
> > data_race() instead of *_ONCE() is to prevent KCSAN from considering the
> > accesses when looking for data races.  But that is mostly for debugging
> > accesses, in cases when these accesses are not really part of the
> > concurrent algorithm.
> >
> > So if I understand the situation correctly, I would be using *ONCE().
> 
> Could this be spelled out somewhere in Documentation/ please?

Good point!  I will put a patch together.

							Thanx, Paul

  reply	other threads:[~2020-12-16 21:33 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-06 21:12 [patch 0/3] tick: Annotate and document the intentionaly racy tick_do_timer_cpu Thomas Gleixner
2020-12-06 21:12 ` [patch 1/3] tick: Remove pointless cpu valid check in hotplug code Thomas Gleixner
2020-12-07 11:59   ` Peter Zijlstra
2020-12-07 17:44     ` Thomas Gleixner
2020-12-11 22:21   ` Frederic Weisbecker
2020-12-12  0:16     ` Thomas Gleixner
2020-12-12  1:20       ` Frederic Weisbecker
2020-12-11 22:31   ` Frederic Weisbecker
2020-12-16 10:50   ` [tip: timers/urgent] " tip-bot2 for Thomas Gleixner
2020-12-06 21:12 ` [patch 2/3] tick/sched: Remove bogus boot "safety" check Thomas Gleixner
2020-12-11 22:41   ` Frederic Weisbecker
2020-12-16 10:50   ` [tip: timers/urgent] " tip-bot2 for Thomas Gleixner
2020-12-06 21:12 ` [patch 3/3] tick: Annotate tick_do_timer_cpu data races Thomas Gleixner
2020-12-07 12:09   ` Peter Zijlstra
2020-12-07 17:46     ` Thomas Gleixner
2020-12-07 18:19       ` Marco Elver
2020-12-07 19:43         ` Thomas Gleixner
2020-12-07 19:44         ` Paul E. McKenney
2020-12-07 21:46           ` Thomas Gleixner
2020-12-07 22:38             ` Paul E. McKenney
2020-12-07 22:46               ` Thomas Gleixner
2020-12-07 22:55                 ` Paul E. McKenney
2020-12-08  8:11           ` Peter Zijlstra
2020-12-08 15:03             ` Paul E. McKenney
2020-12-16  0:27               ` Thomas Gleixner
2020-12-16 21:19                 ` Paul E. McKenney
2020-12-16 21:23                   ` Thomas Gleixner
2020-12-16 21:32                     ` Paul E. McKenney [this message]
2020-12-17 10:48                   ` Peter Zijlstra
2020-12-17 14:59                     ` Paul E. McKenney
2020-12-08  8:01         ` Peter Zijlstra
2020-12-07 11:05 ` [patch 0/3] tick: Annotate and document the intentionaly racy tick_do_timer_cpu Marco Elver

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