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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