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

36aa9dfc · Oleg Nesterov <[email protected]> · 2007-05-09 02:34:08 -07:00

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]>
Cc: Srivatsa Vaddagiri <[email protected]>
Cc: "Pallipadi, Venkatesh" <[email protected]>
Cc: Gautham shenoy <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 36aa9dfc39bf473780439f5629c30f59d677e793
Parents: d721304d

Changes

1 files changed · +5 −10

File	Status	Add	Del	Content
kernel/workqueue.c	modified	+5	−10	View file

kernel/workqueue.c

View file

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 1d1933c..398c34f 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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;
+	}
 }
 
 /**