path: root/mm/oom_kill.c
diff options
authorTetsuo Handa <>2019-02-01 14:20:31 -0800
committerLinus Torvalds <>2019-02-01 15:46:23 -0800
commit9bcdeb51bd7d2ae9fe65ea4d60643d2aeef5bfe3 (patch)
treeb6dd800d2211e06595a4a5eec4cdecf8257333e8 /mm/oom_kill.c
parent80409c65e2c6cd1540045ee01fc55e50d95e0983 (diff)
oom, oom_reaper: do not enqueue same task twice
Arkadiusz reported that enabling memcg's group oom killing causes strange memcg statistics where there is no task in a memcg despite the number of tasks in that memcg is not 0. It turned out that there is a bug in wake_oom_reaper() which allows enqueuing same task twice which makes impossible to decrease the number of tasks in that memcg due to a refcount leak. This bug existed since the OOM reaper became invokable from task_will_free_mem(current) path in out_of_memory() in Linux 4.7, T1@P1 |T2@P1 |T3@P1 |OOM reaper ----------+----------+----------+------------ # Processing an OOM victim in a different memcg domain. try_charge() mem_cgroup_out_of_memory() mutex_lock(&oom_lock) try_charge() mem_cgroup_out_of_memory() mutex_lock(&oom_lock) try_charge() mem_cgroup_out_of_memory() mutex_lock(&oom_lock) out_of_memory() oom_kill_process(P1) do_send_sig_info(SIGKILL, @P1) mark_oom_victim(T1@P1) wake_oom_reaper(T1@P1) # T1@P1 is enqueued. mutex_unlock(&oom_lock) out_of_memory() mark_oom_victim(T2@P1) wake_oom_reaper(T2@P1) # T2@P1 is enqueued. mutex_unlock(&oom_lock) out_of_memory() mark_oom_victim(T1@P1) wake_oom_reaper(T1@P1) # T1@P1 is enqueued again due to oom_reaper_list == T2@P1 && T1@P1->oom_reaper_list == NULL. mutex_unlock(&oom_lock) # Completed processing an OOM victim in a different memcg domain. spin_lock(&oom_reaper_lock) # T1P1 is dequeued. spin_unlock(&oom_reaper_lock) but memcg's group oom killing made it easier to trigger this bug by calling wake_oom_reaper() on the same task from one out_of_memory() request. Fix this bug using an approach used by commit 855b018325737f76 ("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). As a side effect of this patch, this patch also avoids enqueuing multiple threads sharing memory via task_will_free_mem(current) path. Link: Link: Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") Signed-off-by: Tetsuo Handa <> Reported-by: Arkadiusz Miskiewicz <> Tested-by: Arkadiusz Miskiewicz <> Acked-by: Michal Hocko <> Acked-by: Roman Gushchin <> Cc: Tejun Heo <> Cc: Aleksa Sarai <> Cc: Jay Kamat <> Cc: Johannes Weiner <> Cc: <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/oom_kill.c')
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f0e8cd9edb1a..059e617a1847 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -647,8 +647,8 @@ static int oom_reaper(void *unused)
static void wake_oom_reaper(struct task_struct *tsk)
- /* tsk is already queued? */
- if (tsk == oom_reaper_list || tsk->oom_reaper_list)
+ /* mm is already queued? */
+ if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))