Re: [PATCH 1/8] PM: Add suspend block api.

[Oleg Nesterov]

On 04/30, Tejun Heo wrote:
>
> On 04/29/2010 11:16 PM, Rafael J. Wysocki wrote:
> >>> Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
> >>> it may be used just as well for the opportunistic suspend.  It is freezable,
> >>> but would it hurt?
> >>
> > Freezable workqueues have to be singlethread or else there will be unfixable
> > races, so you can safely assume things will stay as they are in this respect.
>
> Rafael, can you elaborate a bit more on this?  Just in case I missed
> something while doing cmwq as it currently doesn't have such limit.

Currently _cpu_down() can't flush and/or stop the frozen cwq->thread.

IIRC this is fixable, but needs the nasty complications. We should
thaw + stop the frozen cwq->thread, then move the pending works to
another CPU.

Oleg.

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