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

[Christoph Lameter <cl@linux.com>]

On Wed, 14 Oct 2015, Linus Torvalds wrote:

> On Wed, Oct 14, 2015 at 10:57 AM, Christoph Lameter <cl@linux.com> wrote:
> >
> > Well yes the schedule_delayed_work_on() call is from another cpu and the
> > schedule_delayed_work() from the same. No confusion there.
>
> So "schedule_delayed_work()" does *not* guarantee that the work will
> run on the same CPU.

That is news to me. As far as I know: The only workqueue that is not
guaranteed to run on the same cpu is an unbound workqueue.

> If you want the scheduled work to happen on a particular CPU, then you
> should use "schedule_delayed_work_on()"  It shouldn't matter which CPU
> you call it from.

Ok then lets audit the kernel for this if that assumption is no longer
true.

> At least that's how I think the rules should be. Very simple, very
> clear: if you require a specific CPU, say so. Don't silently depend on
> "in practice, lots of times we tend to use the local cpu".

As far as I can remember this was guaranteed and not just practice.

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