X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=kernel%2Fsched%2Ffair.c;h=fbc0b8214af0a89fbde855e559884d6e3ca988fa;hb=1effd9f19324;hp=0b069bf3e708e82ea0e08c5b204f931ca1d22a00;hpb=aee38ea95419c818dfdde52b115aeffe9cbb259b;p=deliverable%2Flinux.git

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0b069bf3e708..fbc0b8214af0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1164,9 +1164,19 @@ static void task_numa_compare(struct task_numa_env *env,
 	long moveimp = imp;
 
 	rcu_read_lock();
-	cur = ACCESS_ONCE(dst_rq->curr);
-	if (cur->pid == 0) /* idle */
+
+	raw_spin_lock_irq(&dst_rq->lock);
+	cur = dst_rq->curr;
+	/*
+	 * No need to move the exiting task, and this ensures that ->curr
+	 * wasn't reaped and thus get_task_struct() in task_numa_assign()
+	 * is safe under RCU read lock.
+	 * Note that rcu_read_lock() itself can't protect from the final
+	 * put_task_struct() after the last schedule().
+	 */
+	if ((cur->flags & PF_EXITING) || is_idle_task(cur))
 		cur = NULL;
+	raw_spin_unlock_irq(&dst_rq->lock);
 
 	/*
 	 * "imp" is the fault differential for the source task between the