X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=kernel%2Fcpuset.c;h=ed0ff443f03640f16d0c3f68e95a5c644a948882;hb=d6748066ad0e8b2514545998f8367ebb3906f299;hp=10131fdaff70c36dc9fb181ace777015296891e3;hpb=0a7a0519d1789f3a222849421dbe91b6bddb88f5;p=firefly-linux-kernel-4.4.55.git

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 10131fdaff70..ed0ff443f036 100644
--- a/kernel/cpuset.c
+++ b/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 @@ repeat:
 	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 @@ repeat:
 
 	/*
 	 * 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();