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From: Oleg Nesterov <oleg@redhat.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: mingo@kernel.org, peterz@infradead.org,
	linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH 1/2] sched: Introduce rcuwait machinery
Date: Tue, 17 Jan 2017 18:41:20 +0100
Message-ID: <20170117174120.GB4754@redhat.com> (raw)
In-Reply-To: <20170116013232.GA7295@linux-80c1.suse>

On 01/15, Davidlohr Bueso wrote:
>
> On Thu, 22 Dec 2016, Bueso wrote:
>
>> +	WARN_ON(current->exit_state);                                   \
>
> While not related to this patch, but per 3245d6acab9 (exit: fix race
> between wait_consider_task() and wait_task_zombie()), should we not
> *_ONCE() all things ->exit_state?

current->exit_state != 0 is stable. I mean, only current can change it
from zero to non-zero, and once it is non-zero it can't be zero again.

> I'm not really refering to a specific
> bug (much less here, where that race would not matter obviously), but
> if nothing else, for documentation

Oh, I won't argue but I do not agree. To me, READ_ONCE() often adds some
confusion because I can almost never understand if it is actually needed
for correctness or it was added "just in case".

Oleg.

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-22 17:01 [PATCH 0/2] sched: Introduce rcuwait Davidlohr Bueso
2016-12-22 17:01 ` [PATCH 1/2] sched: Introduce rcuwait machinery Davidlohr Bueso
2016-12-22 19:27   ` kbuild test robot
2017-01-03 23:20     ` Davidlohr Bueso
2016-12-22 19:55   ` kbuild test robot
2017-01-16  1:32   ` Davidlohr Bueso
2017-01-17 17:41     ` Oleg Nesterov [this message]
2016-12-22 17:01 ` [PATCH 2/2] locking/percpu-rwsem: Replace waitqueue with rcuwait Davidlohr Bueso
2017-01-09 18:26 ` [PATCH 0/2] sched: Introduce rcuwait Davidlohr Bueso
2017-01-10 18:35   ` Oleg Nesterov
2017-01-10 19:37     ` Davidlohr Bueso
2017-01-11 15:22 [PATCH v2 " Davidlohr Bueso
2017-01-11 15:22 ` [PATCH 1/2] sched: Introduce rcuwait machinery Davidlohr Bueso

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