mm, memcg: don't take task_lock in task_in_mem_cgroup
For processes that have detached their mm's, task_in_mem_cgroup()
unnecessarily takes task_lock() when rcu_read_lock() is all that is
necessary to call mem_cgroup_from_task().
While we're here, switch task_in_mem_cgroup() to return bool.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1947218..4748966 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1448,11 +1448,12 @@
return ret;
}
-int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)
+bool task_in_mem_cgroup(struct task_struct *task,
+ const struct mem_cgroup *memcg)
{
- int ret;
struct mem_cgroup *curr = NULL;
struct task_struct *p;
+ bool ret;
p = find_lock_task_mm(task);
if (p) {
@@ -1464,14 +1465,14 @@
* killer still needs to detect if they have already been oom
* killed to prevent needlessly killing additional tasks.
*/
- task_lock(task);
+ rcu_read_lock();
curr = mem_cgroup_from_task(task);
if (curr)
css_get(&curr->css);
- task_unlock(task);
+ rcu_read_unlock();
}
if (!curr)
- return 0;
+ return false;
/*
* We should check use_hierarchy of "memcg" not "curr". Because checking
* use_hierarchy of "curr" here make this function true if hierarchy is