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
> +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?
> + return t->mm == mm;
> +
> + return false;
> +}
> +
> #define K(x) ((x) << (PAGE_SHIFT-10))
> /*
> * Must be called while holding a reference to p, which will be released upon
> @@ -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()?
> /*
> * oom_badness() returns 0 if the thread is unkillable
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