On Saturday, 24 February 2007 09:57, Rafael J. Wysocki wrote:
> On Saturday, 24 February 2007 01:31, Johannes Berg wrote:
> > Hi,
> >
> > > Could you please try the appended patch? It's somewhat hackish, but may work.
> >
> > Not before Monday or Tuesday unfortunately, I'm away from the machine.
>
> Okay, no big deal. I think I'll be able to reproduce the problem here. ;-)
>
> > Maybe I can find someone else willing to test who has the same box.
> >
> > > The idea is to do nothing on CPU unplug if the CPU's worker thread is frozen
> > > and later check in the thread itself if it has been replaced by another one.
> >
> > Yeah that should work. That patch won't apply to my tree though unless I
> > actually go to -mm2 as well :)
>
> Ah, sorry. I'll prepare a version against 2.6.21-rc1. Apart from this, I
> think there's a better solution, but I have to verify that.
No, this one is better IMO.
Appended is the version against 2.6.21-rc1. It seems to work for me, but I'd
like someone else to confirm it.
Greetings,
Rafael
kernel/workqueue.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
Index: linux-2.6.21-rc1/kernel/workqueue.c
===================================================================
--- linux-2.6.21-rc1.orig/kernel/workqueue.c
+++ linux-2.6.21-rc1/kernel/workqueue.c
@@ -376,8 +376,19 @@ static int worker_thread(void *__cwq)
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
- if (cwq->freezeable)
- try_to_freeze();
+ if (try_to_freeze()) {
+ /* We've just left the refrigerator. If our CPU is
+ * a nonboot one, we might have been replaced.
+ * The lock is taken to prevent the race with
+ * cleanup_workqueue_thread() from happening
+ */
+ spin_lock_irq(&cwq->lock);
+ if (cwq->thread != current) {
+ spin_unlock_irq(&cwq->lock);
+ break;
+ }
+ spin_unlock_irq(&cwq->lock);
+ }
add_wait_queue(&cwq->more_work, &wait);
if (list_empty(&cwq->worklist))
@@ -539,6 +550,9 @@ static void cleanup_workqueue_thread(str
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
spin_lock_irqsave(&cwq->lock, flags);
p = cwq->thread;
+ if (p && frozen(p))
+ p = NULL;
+
cwq->thread = NULL;
spin_unlock_irqrestore(&cwq->lock, flags);
if (p)
