The patch titled
Subject: oom, oom_reaper: do not enqueue same task twice
has been added to the -mm tree. Its filename is
oom-oom_reaper-do-not-enqueue-same-task-twice.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/oom-oom_reaper-do-not-enqueue-same-task-twice.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/oom-oom_reaper-do-not-enqueue-same-task-twice.patch
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From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: 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, 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: http://lkml.kernel.org/r/e865a044-2c10-9858-f4ef-254bc71d6cc2@xxxxxxxxxxxxxxxxxxx
Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-by: Arkadiusz Miskiewicz <arekm@xxxxxxxx>
Tested-by: Arkadiusz Miskiewicz <arekm@xxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Aleksa Sarai <asarai@xxxxxxx>
Cc: Jay Kamat <jgkamat@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched/coredump.h | 1 +
mm/oom_kill.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)
--- a/include/linux/sched/coredump.h~oom-oom_reaper-do-not-enqueue-same-task-twice
+++ a/include/linux/sched/coredump.h
@@ -71,6 +71,7 @@ static inline int get_dumpable(struct mm
#define MMF_HUGE_ZERO_PAGE 23 /* mm has ever used the global huge zero page */
#define MMF_DISABLE_THP 24 /* disable THP for all VMAs */
#define MMF_OOM_VICTIM 25 /* mm is the oom victim */
+#define MMF_OOM_REAP_QUEUED 26 /* mm was queued for oom_reaper */
#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP)
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
--- a/mm/oom_kill.c~oom-oom_reaper-do-not-enqueue-same-task-twice
+++ a/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))
return;
get_task_struct(tsk);
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
oom-oom_reaper-do-not-enqueue-same-task-twice.patch
info-task-hung-in-generic_file_write_iter.patch
info-task-hung-in-generic_file_write-fix.patch
