> On 08/24, taoyue wrote:
>
>> Oleg Nesterov wrote:
>>
>>>> collect_signal: sigqueue_free:
>>>>
>>>> list_del_init(&first->list);
>>>> spin_lock_irqsave(lock, flags);
>>>>
>>>>
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>
>>>
>>>> if (!list_empty(&q->list))
>>>> list_del_init(&q->list);
>>>> spin_unlock_irqrestore(lock,
>>>> flags);
>>>> q->flags &= ~SIGQUEUE_PREALLOC;
>>>>
>>>> __sigqueue_free(first); __sigqueue_free(q);
>>>>
>>>>
>>> collect_signal() is always called under ->siglock which is also taken by
>>> sigqueue_free(), so this is not possible.
>>>
>>> Basically, this patch is the same one-liner I sent you before
>>>
>>>
http://marc.info/?l=linux-kernel&m=118772206603453&w=2
>>>
>>> (Thanks for the additional testing and report, btw).
>>>
>>> P.S. It would be nice to know if this patch solves the problems reported
>>> by Jeremy, but his email is disabled.
>>>
>>> Oleg.
>>>
>>>
>>>
>> I know, using current->sighand->siglock to prevent one sigqueue
>> is free twice. I want to know whether it is possible that the two
>> function is called in different thread. If that, the spin_lock is useless.
>>
>
> Not sure I understand. Yes, it is possible they are called by 2 different
> threads, that is why we had a race. But all threads in the same thread
> group have the same ->sighand, and thus the same ->sighand->siglock.
>
