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    SubjectRe: Problem with freezable workqueues
    Date
    On Wednesday, 28 February 2007 14:17, Srivatsa Vaddagiri wrote:
    > On Wed, Feb 28, 2007 at 12:11:03PM +0100, Rafael J. Wysocki wrote:
    > > > In addition to thawing worker thread before kthread_stopping it, there
    > > > are minor changes required in worker threads, to check for
    > > > is_cpu_offline(bind_cpu) when they come out of refrigerator and jump to
    > > > wait_to_die if so (ex: softirq.c).
    > > >
    > > > I guess you would need these changes before freezer-based hotplug is
    > > > merged, in which case Gautham can send those patches out first.
    > >
    > > Yes, please, if that's possible.
    >
    > After looking at the current workqueue code, the above minor change I
    > suggested is not required.
    >
    > So you should be able to fix your "kthread_stop on a frozen worker
    > thread hangs" problem by just a simple patch like this (against
    > 2.6.20-mm2):
    >
    >
    > --- workqueue.c.org 2007-02-28 18:32:48.000000000 +0530
    > +++ workqueue.c 2007-02-28 18:44:23.000000000 +0530
    > @@ -718,6 +718,8 @@ static void cleanup_workqueue_thread(str
    > insert_wq_barrier(cwq, &barr, 1);
    > cwq->should_stop = 1;
    > alive = 1;
    > + if (frozen(cwq->thread))
    > + thaw(cwq->thread);
    > }
    > spin_unlock_irq(&cwq->lock);
    >
    >
    > Can you test with this?

    Sure, I will.

    > Note that as Oleg commented, freezable workqueues are broken w/o his
    > patch here:
    >
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=116855740612755
    >
    > So you need to have Andrew/Linux pick up the above patch first to have
    > correctly functioning freezable workqueues.

    This one already is in -mm.
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