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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.cz>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>, Shaohua Li <shli@fb.com>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [GIT PULL] workqueue fixes for v4.3-rc5
Date: Wed, 14 Oct 2015 12:01:11 -0700	[thread overview]
Message-ID: <CA+55aFwed4Q=T48QxNqhL3UL_f1XqQEBJ6mnA42iWiOAiZZO9A@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFz+_Zh7O544QL3YCjTr1rfb-Q82wAyHTK8QMr+9X81h2g@mail.gmail.com>

On Wed, Oct 14, 2015 at 11:37 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Yes, yes, it so _happens_ that "add_timer()" preferentially uses the
> current CPU etc, so in practice it may have happened to work. But
> there's absolutely zero reason to think it should always work that
> way.

Side note: even in practice, I think things like off-lining CPU's etc
(which some mobile environments seem to do as a power saving thing)
can end up moving timers to other CPU's even if they originally got
added on a particular cpu.

So I really think that the whole "schedule_delayed_work() ends up
running on the CPU" has actually never "really" been true. It has at
most been a "most of the time" thing, making it hard to see the
problem in practice.

                Linus

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  parent reply	other threads:[~2015-10-14 19:01 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20151013214952.GB23106@mtj.duckdns.org>
2015-10-14 16:30 ` Linus Torvalds
2015-10-14 16:57   ` Tejun Heo
2015-10-14 17:36     ` Linus Torvalds
2015-10-14 17:57       ` Christoph Lameter
2015-10-14 18:37         ` Linus Torvalds
2015-10-14 18:58           ` Christoph Lameter
2015-10-14 19:01           ` Linus Torvalds [this message]
2015-10-14 19:02       ` Tejun Heo
2015-10-14 19:16         ` Linus Torvalds
2015-10-14 19:38           ` Tejun Heo
2015-10-14 20:10             ` Linus Torvalds
2015-10-14 20:24               ` Tejun Heo
2015-10-19  3:51                 ` Mike Galbraith
2015-10-16 19:51               ` [PATCH] vmstat_update: ensure work remains on the same core Chris Metcalf
2015-10-16 19:54                 ` Linus Torvalds
2015-10-14 18:03   ` [GIT PULL] workqueue fixes for v4.3-rc5 Christoph Lameter
2015-10-14 18:40     ` Linus Torvalds
2015-10-14 18:59       ` Christoph Lameter
2015-10-14 19:10         ` Linus Torvalds

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