[PATCH] rcuperf: Do not wake up shutdown wait queue if "shutdown" is false.

[Artem Savkov <artem.savkov@gmail.com>]

After finishing it's tests rcuperf tries to wake up shutdown_wq even if
"shutdown" param is set to false, resulting in a wake_up() call on an
unitialized wait_queue_head_t which leads to "BUG: spinlock bad magic" and
"BUG: unable to handle kernel NULL pointer dereference".

Fix by checking "shutdown" param before waking up the queue.

Signed-off-by: Artem Savkov <artem.savkov@gmail.com>
---
 kernel/rcu/rcuperf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index 09ffa36..fb45a26 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -414,8 +414,10 @@ rcu_perf_writer(void *arg)
 					b_rcu_perf_writer_finished =
 						cur_ops->completed();
 				}
-				smp_mb(); /* Assign before wake. */
-				wake_up(&shutdown_wq);
+				if (shutdown) {
+					smp_mb(); /* Assign before wake. */
+					wake_up(&shutdown_wq);
+				}
 			}
 		}
 		if (done && !alldone &&
-- 
2.7.0