2.6.37-stable review patch. If anyone has any objections, please let us know.
------------------ From: Eric Dumazet <[email protected]> [ Upstream commit 2c6607c611cb7bf0a6750bcea34a258144e302c5 ] Leonardo Chiquitto found poll() could block forever on tcp sockets and Urgent data was received, if the event flag only contains POLLPRI. He did a bisection and found commit 4938d7e0233 (poll: avoid extra wakeups in select/poll) was the source of the problem. Problem is TCP sockets use standard sock_def_readable() function for their sk_data_ready() handler, and sock_def_readable() doesnt signal POLLPRI. Only TCP is affected by the problem. Adding POLLPRI to the list of flags might trigger unnecessary schedules, but URGENT handling is such a seldom used feature this seems a good compromise. Thanks a lot to Leonardo for providing the bisection result and a test program as well. Reference : http://www.spinics.net/lists/netdev/msg151793.html Reported-and-bisected-by: Leonardo Chiquitto <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Tested-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- net/core/sock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1907,7 +1907,7 @@ static void sock_def_readable(struct soc rcu_read_lock(); wq = rcu_dereference(sk->sk_wq); if (wq_has_sleeper(wq)) - wake_up_interruptible_sync_poll(&wq->wait, POLLIN | + wake_up_interruptible_sync_poll(&wq->wait, POLLIN | POLLPRI | POLLRDNORM | POLLRDBAND); sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); rcu_read_unlock(); _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
