Merge tag 'for-linus-v4.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayto...

[platform/kernel/linux-starfive.git] / kernel / cgroup / cpuset.c

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 5fd1bdb..ca8376e 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1038,38 +1038,25 @@ static void cpuset_post_attach(void)
  * @tsk: the task to change
  * @newmems: new nodes that the task will be set
  *
- * In order to avoid seeing no nodes if the old and new nodes are disjoint,
- * we structure updates as setting all new allowed nodes, then clearing newly
- * disallowed ones.
+ * We use the mems_allowed_seq seqlock to safely update both tsk->mems_allowed
+ * and rebind an eventual tasks' mempolicy. If the task is allocating in
+ * parallel, it might temporarily see an empty intersection, which results in
+ * a seqlock check and retry before OOM or allocation failure.
  */
 static void cpuset_change_task_nodemask(struct task_struct *tsk,
                                        nodemask_t *newmems)
 {
-       bool need_loop;
-
        task_lock(tsk);
-       /*
-        * Determine if a loop is necessary if another thread is doing
-        * read_mems_allowed_begin().  If at least one node remains unchanged and
-        * tsk does not have a mempolicy, then an empty nodemask will not be
-        * possible when mems_allowed is larger than a word.
-        */
-       need_loop = task_has_mempolicy(tsk) ||
-                       !nodes_intersects(*newmems, tsk->mems_allowed);
 
-       if (need_loop) {
-               local_irq_disable();
-               write_seqcount_begin(&tsk->mems_allowed_seq);
-       }
+       local_irq_disable();
+       write_seqcount_begin(&tsk->mems_allowed_seq);
 
        nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
        mpol_rebind_task(tsk, newmems);
        tsk->mems_allowed = *newmems;
 
-       if (need_loop) {
-               write_seqcount_end(&tsk->mems_allowed_seq);
-               local_irq_enable();
-       }
+       write_seqcount_end(&tsk->mems_allowed_seq);
+       local_irq_enable();
 
        task_unlock(tsk);
 }