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SubjectRe: [patch] NE2000
Jorge Nerin wrote:
>
> ...
> So I think that it could be a little window near sock_wait_for_wmem that
> could be SMP insecure wich is affecting me.
>
> The code of sock_wait_for_wmem in 2.4.0-test10 is this:
>
> static long sock_wait_for_wmem(struct sock * sk, long timeo)
> {
> DECLARE_WAITQUEUE(wait, current);
>
> clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
> add_wait_queue(sk->sleep, &wait);
> for (;;) {
> if (signal_pending(current))
> break;
> set_bit(SOCK_NOSPACE, &sk->socket->flags);
> set_current_state(TASK_INTERRUPTIBLE);
> if (atomic_read(&sk->wmem_alloc) < sk->sndbuf)
> break;
> if (sk->shutdown & SEND_SHUTDOWN)
> break;
> if (sk->err)
> break;
> timeo = schedule_timeout(timeo);
> }
> __set_current_state(TASK_RUNNING);
> remove_wait_queue(sk->sleep, &wait);
> return timeo;
> }
>
> Does someone see something SMP insecure? Perhaps I'm totally wrong, this
> could also be somewhere in the interrupt handling, don't know.

No, that code is correct, provided (current->state == TASK_RUNNING)
on entry. If it isn't, there's a race window which can cause
lost wakeups. As a check you could add:

if ((current->state & (TASK_INTERRUPTIBLE|TASK_UNINTERRUPTIBLE)) == 0)
BUG();
to the start of this function.
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