This is a note to let you know that I've just added the patch titled
net: add POLLPRI to sock_def_readable()
to the 2.6.37-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-add-pollpri-to-sock_def_readable.patch
and it can be found in the queue-2.6.37 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 4429b20f7c404b6e9b1926931eb3065e346c12fc Mon Sep 17 00:00:00 2001
From: Eric Dumazet <[email protected]>
Date: Thu, 6 Jan 2011 10:54:29 -0800
Subject: net: add POLLPRI to sock_def_readable()
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();
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.37/net_sched-pfifo_head_drop-problem.patch
queue-2.6.37/net-add-pollpri-to-sock_def_readable.patch
queue-2.6.37/ipv4-ip-defragmentation-must-be-ecn-aware.patch
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