From: yuan linyu <cug...@163.com> Date: Thu, 14 Dec 2017 22:22:16 +0800
> From: yuan linyu <linyu.y...@alcatel-sbell.com.cn> > > from logical view, if sock_writeable(&q->sk) return false, > original second condition will return false too, > change it and make second condition can return true. > > Signed-off-by: yuan linyu <linyu.y...@alcatel-sbell.com.cn> ... > @@ -587,8 +587,7 @@ static unsigned int tap_poll(struct file *file, > poll_table *wait) > mask |= POLLIN | POLLRDNORM; > > if (sock_writeable(&q->sk) || > - (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) && > - sock_writeable(&q->sk))) > + !test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags)) > mask |= POLLOUT | POLLWRNORM; > > out: > -- > 2.7.4 Hmmm, this same exact test also exists in tun_chr_poll(). The second condition probably never trigger, because of the reasons you have listed. The only side effect is that it will set the ASYNC_NOSPACE bit in the socket flags. Logically, it seems we can remove the second condition altogether. But I wonder what might break if we stop trying to set that socket flags bit in this situation. Overall, I'm not sure this change is safe at all.
