linux-kernel - Re: [GIT PULL] workqueue fixes for v4.3-rc5

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Date:	Wed, 14 Oct 2015 12:01:11 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Shaohua Li <shli@...com>, linux-mm <linux-mm@...ck.org>
Subject: Re: [GIT PULL] workqueue fixes for v4.3-rc5

On Wed, Oct 14, 2015 at 11:37 AM, Linus Torvalds
<torvalds@...ux-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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