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.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Gautham shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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 @@
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;
+ }
}
/**