From: Michal Hocko <mhocko@xxxxxxxx>
Burt Holzman has noticed that memcg v1 doesn't notify about OOM events
via eventfd anymore. The reason is that 29ef680ae7c2 ("memcg, oom: move
out_of_memory back to the charge path") has moved the oom handling back
to the charge path. While doing so the notification was left behind in
mem_cgroup_oom_synchronize.
Fix the issue by replicating the oom hierarchy locking and the
notification.
Reported-by: Burt Holzman <burt@xxxxxxxx>
Fixes: 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path")
Cc: stable # 4.19+
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
Hi Andrew,
I forgot to CC you on the patch sent as a reply to the original bug
report [1] so I am reposting with Ack from Johannes. Burt has confirmed
this is resolving the regression for him [2]. 4.20 is out but I have
marked the patch for stable so it should hit both 4.19 and 4.20.
[1] http://lkml.kernel.org/r/20181221153302.GB6410@xxxxxxxxxxxxxx
[2] http://lkml.kernel.org/r/96D4815C-420F-41B7-B1E9-A741E7523596@xxxxxxxxxxxxxxxxx
mm/memcontrol.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6e1469b80cb7..7e6bf74ddb1e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1666,6 +1666,9 @@ enum oom_status {
static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
{
+ enum oom_status ret;
+ bool locked;
+
if (order > PAGE_ALLOC_COSTLY_ORDER)
return OOM_SKIPPED;
@@ -1700,10 +1703,23 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int
return OOM_ASYNC;
}
+ mem_cgroup_mark_under_oom(memcg);
+
+ locked = mem_cgroup_oom_trylock(memcg);
+
+ if (locked)
+ mem_cgroup_oom_notify(memcg);
+
+ mem_cgroup_unmark_under_oom(memcg);
if (mem_cgroup_out_of_memory(memcg, mask, order))
- return OOM_SUCCESS;
+ ret = OOM_SUCCESS;
+ else
+ ret = OOM_FAILED;
- return OOM_FAILED;
+ if (locked)
+ mem_cgroup_oom_unlock(memcg);
+
+ return ret;
}
/**
--
2.19.2
