Messages in this thread | | | Date | Wed, 30 Sep 2015 15:59:37 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in |
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On 09/30, Tetsuo Handa wrote: > > Oleg Nesterov wrote: > > Both "child->mm == mm" and "p->mm != mm" checks in oom_kill_process() > > are wrong. ->mm can be if task is the exited group leader. This means > > can be [missing word here?] if task
Yes thanks. Will fix in v2.
Hmm. And I just noticed that the subjects were corrupted... need to fix my script.
> > +static bool process_has_mm(struct task_struct *p, struct mm_struct *mm) > > +{ > > + struct task_struct *t; > > + > > + for_each_thread(p, t) > > + if (t->mm) > > Can t->mm change between pevious line and next line?
Good point, thanks. I'll add READ_ONCE() to ensure gcc won't re-load t->mm again.
> > @@ -530,7 +541,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, > > list_for_each_entry(child, &t->children, sibling) { > > unsigned int child_points; > > > > - if (child->mm == p->mm) > > + if (process_has_mm(child, p->mm)) > > continue; > > We hold read_lock(&tasklist_lock) but not rcu_read_lock(). > Is for_each_thread() safe without rcu_read_lock()?
Yes, for_each_thread() is rcu and/or tasklist_lock safe.
Oleg.
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