Oleg Nesterov wrote:
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.
Oleg, if one thread can be in collect_signal() and another in
sigqueue_free() and both operate on the exact same sigqueue object, its
not clear how we prevent two calls to __sigqueue_free() to
the same object. In that case the lock (or some lock) should be around
__sigqueue_free() - no ?
i.e if we enter sigqueue_free(), we will call __sigqueue_free()
regardless of the state.
Oleg.
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