Messages in this thread | | | Date | Wed, 7 Mar 2018 12:56:21 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH] mm: oom: Fix race condition between oom_badness and do_exit of task |
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On Wed, 7 Mar 2018, Gaurav Kohli wrote:
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 6fd9773..5f4cc4b 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -114,9 +114,11 @@ struct task_struct *find_lock_task_mm(struct task_struct *p) > > for_each_thread(p, t) { > task_lock(t); > + get_task_struct(t); > if (likely(t->mm)) > goto found; > task_unlock(t); > + put_task_struct(t); > } > t = NULL; > found:
We hold rcu_read_lock() here, so perhaps only do get_task_struct() before doing rcu_read_unlock() and we have a non-NULL t?
> @@ -191,6 +193,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > test_bit(MMF_OOM_SKIP, &p->mm->flags) || > in_vfork(p)) { > task_unlock(p); > + put_task_struct(p); > return 0; > } > > @@ -208,7 +211,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > */ > if (has_capability_noaudit(p, CAP_SYS_ADMIN)) > points -= (points * 3) / 100; > - > + put_task_struct(p); > /* Normalize to oom_score_adj units */ > adj *= totalpages / 1000; > points += adj;
This fixes up oom_badness(), but there are other users of find_lock_task_mm() in the oom killer as well as other subsystems.
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