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Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in

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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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[PATCH -mm 0/3] mm/oom_kill: ensure we actually kill all tasks  sharing the same mm Oleg Nesterov <oleg@redhat.com> - 2015-09-29 16:30 +0200
  [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in Oleg Nesterov <oleg@redhat.com> - 2015-09-29 16:30 +0200
    Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm checks  in David Rientjes <rientjes@google.com> - 2015-09-30 00:50 +0200
      Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm  checks in Oleg Nesterov <oleg@redhat.com> - 2015-09-30 16:00 +0200
    Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-30 04:20 +0200
      Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm  checks in Oleg Nesterov <oleg@redhat.com> - 2015-09-30 16:10 +0200
  [PATCH -mm 2/3] mm/oom_kill: cleanup the "kill sharing same memory" Oleg Nesterov <oleg@redhat.com> - 2015-09-29 16:30 +0200
    Re: [PATCH -mm 2/3] mm/oom_kill: cleanup the "kill sharing same  memory" David Rientjes <rientjes@google.com> - 2015-09-30 00:40 +0200
      Re: [PATCH -mm 2/3] mm/oom_kill: cleanup the "kill sharing same  memory" Oleg Nesterov <oleg@redhat.com> - 2015-09-30 16:00 +0200
  [PATCH -mm v2 0/3] mm/oom_kill: ensure we actually kill all tasks  sharing the same mm Oleg Nesterov <oleg@redhat.com> - 2015-09-30 20:30 +0200

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