workqueue: don't clear cwq->thread until it exits

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.

Oleg Nesterov committed 19 years ago

Commit 36aa9df1 parent d7213041 file · +5 −10Browse files

Showing the changes to kernel/workqueue.c (1 of 1 file). Show all

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kernel/workqueue.c+5−10

 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
 {
-	struct cpu_workqueue_struct *cwq;
+	struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
-	unsigned long flags;
-	struct task_struct *p;
-	cwq = per_cpu_ptr(wq->cpu_wq, cpu);
+	if (cwq->thread) {
-	spin_lock_irqsave(&cwq->lock, flags);
+		kthread_stop(cwq->thread);
-	p = cwq->thread;
+		cwq->thread = NULL;
-	cwq->thread = NULL;
+	}
-	spin_unlock_irqrestore(&cwq->lock, flags);
-	if (p)
-		kthread_stop(p);
 }
 /**