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-rw-r--r--mm/memcontrol.c35
1 files changed, 31 insertions, 4 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9b35da28b587..b58d4fbe6c48 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -292,6 +292,9 @@ struct mem_cgroup {
/* vmpressure notifications */
struct vmpressure vmpressure;
+ /* css_online() has been completed */
+ int initialized;
+
/*
* the counter to account for mem+swap usage.
*/
@@ -1127,9 +1130,21 @@ skip_node:
* skipping css reference should be safe.
*/
if (next_css) {
- if ((next_css == &root->css) ||
- ((next_css->flags & CSS_ONLINE) && css_tryget(next_css)))
- return mem_cgroup_from_css(next_css);
+ struct mem_cgroup *memcg = mem_cgroup_from_css(next_css);
+
+ if (next_css == &root->css)
+ return memcg;
+
+ if (css_tryget(next_css)) {
+ /*
+ * Make sure the memcg is initialized:
+ * mem_cgroup_css_online() orders the the
+ * initialization against setting the flag.
+ */
+ if (smp_load_acquire(&memcg->initialized))
+ return memcg;
+ css_put(next_css);
+ }
prev_css = next_css;
goto skip_node;
@@ -6538,6 +6553,7 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(css));
+ int ret;
if (css->cgroup->id > MEM_CGROUP_ID_MAX)
return -ENOSPC;
@@ -6574,7 +6590,18 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
}
mutex_unlock(&memcg_create_mutex);
- return memcg_init_kmem(memcg, &mem_cgroup_subsys);
+ ret = memcg_init_kmem(memcg, &mem_cgroup_subsys);
+ if (ret)
+ return ret;
+
+ /*
+ * Make sure the memcg is initialized: mem_cgroup_iter()
+ * orders reading memcg->initialized against its callers
+ * reading the memcg members.
+ */
+ smp_store_release(&memcg->initialized, 1);
+
+ return 0;
}
/*