---

yaml
---
r: 273248
b: refs/heads/master
c: 89e8a24
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 61600f578fbd2e8ad0c90bddb9c729e7628d3813
+refs/heads/master: 89e8a244b97e48f1f30e898b6f32acca477f2a13

trunk/kernel/cpuset.c

@@ -949,6 +949,8 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
 static void cpuset_change_task_nodemask(struct task_struct *tsk,
 					nodemask_t *newmems)
 {
+	bool masks_disjoint = !nodes_intersects(*newmems, tsk->mems_allowed);
+
 repeat:
 	/*
 	 * Allow tasks that have access to memory reserves because they have
@@ -963,7 +965,6 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk,
 	nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
 	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
 
-
 	/*
 	 * ensure checking ->mems_allowed_change_disable after setting all new
 	 * allowed nodes.
@@ -980,9 +981,11 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk,
 
 	/*
 	 * Allocation of memory is very fast, we needn't sleep when waiting
-	 * for the read-side.
+	 * for the read-side.  No wait is necessary, however, if at least one
+	 * node remains unchanged.
 	 */
-	while (ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
+	while (masks_disjoint &&
+			ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
 		task_unlock(tsk);
 		if (!task_curr(tsk))
 			yield();