Merge branch 'acpi-scan' to satisfy dependencies.

1 files changed, 13 insertions, 1 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index f89014a2c238..e190d1ef3a23 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -260,6 +260,15 @@ retry:
 	err = 0;
 	__cpu_stop_queue_work(stopper1, work1, &wakeq);
 	__cpu_stop_queue_work(stopper2, work2, &wakeq);
+	/*
+	 * The waking up of stopper threads has to happen
+	 * in the same scheduling context as the queueing.
+	 * Otherwise, there is a possibility of one of the
+	 * above stoppers being woken up by another CPU,
+	 * and preempting us. This will cause us to n ot
+	 * wake up the other stopper forever.
+	 */
+	preempt_disable();
 unlock:
 	raw_spin_unlock(&stopper2->lock);
 	raw_spin_unlock_irq(&stopper1->lock);
@@ -270,7 +279,10 @@ unlock:
 		goto retry;
 	}
 
-	wake_up_q(&wakeq);
+	if (!err) {
+		wake_up_q(&wakeq);
+		preempt_enable();
+	}
 
 	return err;
 }