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Message-ID: <1294335897.3074.83.camel@edumazet-laptop>
Date: Thu, 06 Jan 2011 18:44:57 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Leonardo Chiquitto <leonardo.lists@...il.com>,
David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH] net: add POLLPRI to sock_def_readable()
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 <leonardo.lists@...il.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Tested-by: Eric Dumazet <eric.dumazet@...il.com>
---
net/core/sock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index e5af8d5..7fd3541 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1907,7 +1907,7 @@ static void sock_def_readable(struct sock *sk, int len)
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();
--
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