Need to check kthread_should_stop after schedule_timeout() before calling schedule(). This causes threads to sleep with potentially no one to wake them up causing mount(2) to hang in btrfs_stop_workers waiting for threads to stop. Race, IMO, is more evident on UP than on SMP.

Signed-off-by: Amit Gud <gud@ksu.edu>

diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index c84ca1f..4c1f3e5 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -195,6 +195,9 @@ again_locked:
 				if (!list_empty(&worker->pending))
 					continue;
 
+				if (kthread_should_stop())
+					return 0;
+
 				/* still no more work?, sleep for real */
 				spin_lock_irq(&worker->lock);
 				set_current_state(TASK_INTERRUPTIBLE);