sched: Use WRITE_ONCE() for p->on_rq

Since RCU-tasks uses READ_ONCE(p->on_rq), ensure the write-side
matches with WRITE_ONCE().

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/e4896e0b-eacc-45a2-a7a8-de2280a51ecc@paulmck-laptop

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a708d225c28e861922997ed27a25d1b21f072d2a..9d5099d02dbcef9b1f77b820f771de24286bb5bc 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2124,12 +2124,14 @@ void activate_task(struct rq *rq, struct task_struct *p, int flags)
 
        enqueue_task(rq, p, flags);
 
-       p->on_rq = TASK_ON_RQ_QUEUED;
+       WRITE_ONCE(p->on_rq, TASK_ON_RQ_QUEUED);
+       ASSERT_EXCLUSIVE_WRITER(p->on_rq);
 }
 
 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
 {
-       p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
+       WRITE_ONCE(p->on_rq, (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING);
+       ASSERT_EXCLUSIVE_WRITER(p->on_rq);
 
        dequeue_task(rq, p, flags);
 }