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

From: Linus Torvalds
Date: Wed Oct 14 2015 - 15:01:17 EST


On Wed, Oct 14, 2015 at 11:37 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> 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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