On Sunday, 13 May 2007 23:54, Oleg Nesterov wrote:
> On 05/13, Rafael J. Wysocki wrote:
> >
> > On Sunday, 13 May 2007 23:34, Oleg Nesterov wrote:
> > > On 05/13, Rafael J. Wysocki wrote:
> > > >
> > > > @@ -819,20 +843,31 @@ static int __devinit workqueue_cpu_callb
> > > >
> > > > +
> > > > + case CPU_DEAD_FROZEN:
> > > > + if (wq->freezeable) {
> > > > + take_over_work(wq, cpu);
> > > > + thaw_process(cwq->thread);
> > >
> > > Suppose that PF_NOFREEZE task T does flush_workqueue(), and CPU 1 has pending
> > > works. T does flush_cpu_workqueue(0), CPU_DEAD_FROZEN moves works from CPU 1
> > > to CPU 0, T does flush_cpu_workqueue(1) and finds nothing.
> >
> > I don't think this is possible, because we've acquired workqueue_mutex in
> > _cpu_down().
>
> Yes, we did... but flush_workqueue() doesn't take it?
I was looking at the 2.6.21 code, sorry.
Hmm, I guess we could add an additional mutex that would only be taken in
flush_workqueue() and in _cpu_down()/_cpu_up() via workqueue_cpu_callback()
with CPU_LOCK_ACQUIRE?
It doesn't seem to be a good idea to run flush_workqueue() while CPUs are being
taken up and down anyway.
Greetings,
Rafael
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