Pointed out by Srivatsa Vaddagiri.
cleanup_workqueue_thread() sets cwq->thread = NULL and does kthread_stop().
This breaks the "if (cwq->thread == current)" logic in flush_cpu_workqueue()
and leads to deadlock.
Kill the thead first, then clear cwq->thread. workqueue_mutex protects us
from create_workqueue_thread() so we don't need cwq->lock.
Signed-off-by: Oleg Nesterov <[email protected]>
--- mm-6.20-rc3/kernel/workqueue.c~3_thread 2007-01-11 22:22:58.000000000 +0300
+++ mm-6.20-rc3/kernel/workqueue.c 2007-01-12 01:44:39.000000000 +0300
@@ -625,17 +625,12 @@ EXPORT_SYMBOL_GPL(__create_workqueue);
static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
- struct cpu_workqueue_struct *cwq;
- unsigned long flags;
- struct task_struct *p;
+ struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
- cwq = per_cpu_ptr(wq->cpu_wq, cpu);
- spin_lock_irqsave(&cwq->lock, flags);
- p = cwq->thread;
- cwq->thread = NULL;
- spin_unlock_irqrestore(&cwq->lock, flags);
- if (p)
- kthread_stop(p);
+ if (cwq->thread) {
+ kthread_stop(cwq->thread);
+ cwq->thread = NULL;
+ }
}
/**
-
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