On 05/14, Oleg Nesterov wrote:
>
> On 05/13, Rafael J. Wysocki wrote:
> >
> > The suspend/hibernation is broken on SMP due to:
> >
> > commit 3540af8ffddcdbc7573451ac0b5cd57a2eaf8af5
> > tifm: replace per-adapter kthread with freezeable workqueue
> >
> > Well, it looks like freezable worqueues still deadlock with CPU hotplug
> > when worker threads are frozen.
>
> Ugh. I thought we deprecated create_freezeable_workqueue(), exactly
> because suspend was changed to call _cpu_down() after freeze().
>
> It is not that "looks like freezable worqueues still deadlock", it
> is "of course, freezable worqueues deadlocks" on CPU_DEAD.
>
> The ->freezeable is still here just because of incoming "cpu-hotplug
> using freezer" rework.
>
> No?
>
> > --- linux-2.6.22-rc1.orig/kernel/workqueue.c
> > +++ linux-2.6.22-rc1/kernel/workqueue.c
> > @@ -799,9 +799,7 @@ static int __devinit workqueue_cpu_callb
> > struct cpu_workqueue_struct *cwq;
> > struct workqueue_struct *wq;
> >
> > - action &= ~CPU_TASKS_FROZEN;
> > -
> > - switch (action) {
> > + switch (action & ~CPU_TASKS_FROZEN) {
>
> Confused. How can we see, say CPU_UP_PREPARE_FROZEN, if we cleared
> CPU_TASKS_FROZEN bit?
So, unless I missed something stupid, this patch is not 100% right.
I think the better fix (at least for now) is
- #define create_freezeable_workqueue(name) __create_workqueue((name), 0, 1)
+ #define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1)
Alex, do you really need a multithreaded wq?
Rafael, what do you think?
Oleg.
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