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From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Omar Sandoval <osandov@osandov.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Jens Axboe <axboe@fb.com>
Subject: Re: add_wait_queue() (unintentional?) behavior change in v4.13
Date: Wed, 6 Dec 2017 17:43:44 +0100	[thread overview]
Message-ID: <20171206164344.iy57cvwgbsqhtwwz@gmail.com> (raw)
In-Reply-To: <CA+55aFwhq-ZyDW2SYhYDg1ytKybwHywiH9jW3UmMu=YAgk694Q@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Wed, Nov 29, 2017 at 4:58 PM, Omar Sandoval <osandov@osandov.com> wrote:
> >
> > Note the change from __add_wait_queue() to
> > __add_wait_queue_entry_tail(). I'm assuming this was a typo since the
> > commit message doesn't mention any functional changes. This patch
> > restores the old behavior:
> >   [...]
> > I didn't go through and audit callers of add_wait_queue(), but from a
> > quick code read this makes it so that non-exclusive waiters will not be
> > woken up if they are behind enough exclusive waiters, and I bet that'll
> > cause some bugs.
> 
> This sounds right to me.
> 
> Ingo?

Yeah, it's indeed unintended and it's a bug - I have applied the fix and will get 
it to you ASAP.

Thanks,

	Ingo

  parent reply	other threads:[~2017-12-06 16:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-30  0:58 Omar Sandoval
2017-11-30  2:37 ` Linus Torvalds
2017-12-06  7:15   ` [PATCH] sched/wait: fix add_wait_queue() behavior change Omar Sandoval
2017-12-06 16:11     ` Jens Axboe
2017-12-06 16:46       ` Ingo Molnar
2017-12-06 20:28     ` [tip:sched/core] sched/wait: Fix add_wait_queue() behavioral change tip-bot for Omar Sandoval
2017-12-06 16:43   ` Ingo Molnar [this message]
2017-12-06  2:35 ` add_wait_queue() (unintentional?) behavior change in v4.13 Fubo Chen

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