[ 3.5.y.z extended stable ] Patch "RDS: fix rds-ping spinlock recursion" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    RDS: fix rds-ping spinlock recursion

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 27ec01ca8e6ad143bd80219551a7ef306cc1154a Mon Sep 17 00:00:00 2001
From: "jeff.liu" <jeff.liu at oracle.com>
Date: Mon, 8 Oct 2012 18:57:27 +0000
Subject: [PATCH] RDS: fix rds-ping spinlock recursion

commit 5175a5e76bbdf20a614fb47ce7a38f0f39e70226 upstream.

This is the revised patch for fixing rds-ping spinlock recursion
according to Venkat's suggestions.

RDS ping/pong over TCP feature has been broken for years(2.6.39 to
3.6.0) since we have to set TCP cork and call kernel_sendmsg() between
ping/pong which both need to lock "struct sock *sk". However, this
lock has already been hold before rds_tcp_data_ready() callback is
triggerred. As a result, we always facing spinlock resursion which
would resulting in system panic.

Given that RDS ping is only used to test the connectivity and not for
serious performance measurements, we can queue the pong transmit to
rds_wq as a delayed response.

Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
CC: Venkat Venkatsubra <venkat.x.venkatsubra at oracle.com>
CC: David S. Miller <davem at davemloft.net>
CC: James Morris <james.l.morris at oracle.com>
Signed-off-by: Jie Liu <jeff.liu at oracle.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 net/rds/send.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/send.c b/net/rds/send.c
index 96531d4..88eace5 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -1122,7 +1122,7 @@ rds_send_pong(struct rds_connection *conn, __be16 dport)
 	rds_stats_inc(s_send_pong);

 	if (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags))
-		rds_send_xmit(conn);
+		queue_delayed_work(rds_wq, &conn->c_send_w, 0);

 	rds_message_put(rm);
 	return 0;
--
1.7.9.5