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authorJohannes Weiner <jweiner@redhat.com>2011-08-25 15:59:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-08-25 16:25:34 -0700
commit23751be0094012eb6b4756fa80ca54b3eb83069f (patch)
tree30c33d9165bb33d64bd42d6e9bc1e4cbed1c0780 /mm
parent86383b55791bd97e88ef493e33ef521ee244f3d9 (diff)
downloadlinux-linaro-precise-23751be0094012eb6b4756fa80ca54b3eb83069f.tar.gz
memcg: fix hierarchical oom locking
Commit 79dfdaccd1d5 ("memcg: make oom_lock 0 and 1 based rather than counter") tried to oom lock the hierarchy and roll back upon encountering an already locked memcg. The code is confused when it comes to detecting a locked memcg, though, so it would fail and rollback after locking one memcg and encountering an unlocked second one. The result is that oom-locking hierarchies fails unconditionally and that every oom killer invocation simply goes to sleep on the oom waitqueue forever. The tasks practically hang forever without anyone intervening, possibly holding locks that trip up unrelated tasks, too. Signed-off-by: Johannes Weiner <jweiner@redhat.com> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c17
1 files changed, 5 insertions, 12 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0e40f020573..ebd1e86bef1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1841,29 +1841,23 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
*/
static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
{
- int lock_count = -1;
struct mem_cgroup *iter, *failed = NULL;
bool cond = true;
for_each_mem_cgroup_tree_cond(iter, mem, cond) {
- bool locked = iter->oom_lock;
-
- iter->oom_lock = true;
- if (lock_count == -1)
- lock_count = iter->oom_lock;
- else if (lock_count != locked) {
+ if (iter->oom_lock) {
/*
* this subtree of our hierarchy is already locked
* so we cannot give a lock.
*/
- lock_count = 0;
failed = iter;
cond = false;
- }
+ } else
+ iter->oom_lock = true;
}
if (!failed)
- goto done;
+ return true;
/*
* OK, we failed to lock the whole subtree so we have to clean up
@@ -1877,8 +1871,7 @@ static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
}
iter->oom_lock = false;
}
-done:
- return lock_count;
+ return false;
}
/*