[Devel] [PATCH rh7 v2 2/6] memcg: add lock for protecting memcg->oom_notify list

[Vladimir Davydov]

Currently, memcg_oom_lock is used for this, but I'm going to get rid of
it in the following patch, so introduce a dedicated lock.

Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
 mm/memcontrol.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9f2d1d518df4..df98b3dfe0f1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5766,12 +5766,18 @@ static int compare_thresholds(const void *a, const void *b)
 	return 0;
 }
 
+static DEFINE_SPINLOCK(memcg_oom_notify_lock);
+
 static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup_eventfd_list *ev;
 
+	spin_lock(&memcg_oom_notify_lock);
+
 	list_for_each_entry(ev, &memcg->oom_notify, list)
 		eventfd_signal(ev->eventfd, 1);
+
+	spin_unlock(&memcg_oom_notify_lock);
 	return 0;
 }
 
@@ -5957,7 +5963,7 @@ static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
 	if (!event)
 		return -ENOMEM;
 
-	spin_lock(&memcg_oom_lock);
+	spin_lock(&memcg_oom_notify_lock);
 
 	event->eventfd = eventfd;
 	list_add(&event->list, &memcg->oom_notify);
@@ -5965,7 +5971,7 @@ static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
 	/* already in OOM ? */
 	if (atomic_read(&memcg->under_oom))
 		eventfd_signal(eventfd, 1);
-	spin_unlock(&memcg_oom_lock);
+	spin_unlock(&memcg_oom_notify_lock);
 
 	return 0;
 }
@@ -5979,7 +5985,7 @@ static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
 
 	BUG_ON(type != _OOM_TYPE);
 
-	spin_lock(&memcg_oom_lock);
+	spin_lock(&memcg_oom_notify_lock);
 
 	list_for_each_entry_safe(ev, tmp, &memcg->oom_notify, list) {
 		if (ev->eventfd == eventfd) {
@@ -5988,7 +5994,7 @@ static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
 		}
 	}
 
-	spin_unlock(&memcg_oom_lock);
+	spin_unlock(&memcg_oom_notify_lock);
 }
 
 static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
-- 
2.1.4