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Date: Wed, 14 Oct 2015 12:01:11 -0700
Message-ID: <CA+55aFwed4Q=T48QxNqhL3UL_f1XqQEBJ6mnA42iWiOAiZZO9A@mail.gmail.com>
Subject: Re: [GIT PULL] workqueue fixes for v4.3-rc5
From: Linus Torvalds <torvalds@linux-foundation.org>
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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>

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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