Previous patch ignored a situation where oom_has_pending_mm() returns
false due to all threads which mm->oom_mm.victim belongs to have reached
TASK_DEAD state, for there might be other thread groups sharing that mm.
This patch handles such situation by always updating mm->oom_mm.victim.
By applying this patch, the comm/pid pair printed at oom_kill_process()
and oom_reap_task() might differ. But that will not be a critical
problem.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 07e8c1a..0b78133 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -688,6 +688,7 @@ subsys_initcall(oom_init)
void mark_oom_victim(struct task_struct *tsk)
{
struct mm_struct *mm = tsk->mm;
+ struct task_struct *old_tsk;
WARN_ON(oom_killer_disabled);
/* OOM killer might race with memcg OOM */
@@ -705,15 +706,26 @@ void mark_oom_victim(struct task_struct *tsk)
/*
* Since mark_oom_victim() is called from multiple threads,
* connect this mm to oom_mm_list only if not yet connected.
+ *
+ * But task_in_oom_domain(mm->oom_mm.victim, memcg, nodemask) in
+ * oom_has_pending_mm() might return false after all threads in one
+ * thread group (which mm->oom_mm.victim belongs to) reached TASK_DEAD
+ * state. In that case, the same mm will be selected by another thread
+ * group (which mm->oom_mm.victim does not belongs to). Therefore,
+ * we need to replace the old task with the new task (at least when
+ * task_in_oom_domain() returned false).
*/
- if (!mm->oom_mm.victim) {
+ get_task_struct(tsk);
+ spin_lock(&oom_mm_lock);
+ old_tsk = mm->oom_mm.victim;
+ mm->oom_mm.victim = tsk;
+ if (!old_tsk) {
atomic_inc(&mm->mm_count);
- get_task_struct(tsk);
- mm->oom_mm.victim = tsk;
- spin_lock(&oom_mm_lock);
list_add_tail(&mm->oom_mm.list, &oom_mm_list);
- spin_unlock(&oom_mm_lock);
}
+ spin_unlock(&oom_mm_lock);
+ if (old_tsk)
+ put_task_struct(old_tsk);
}
/**
--
1.8.3.1
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