netdev - [PATCH 4/5] Fix netconsole to not deadlock on rmmod

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Message-Id: <1287021713-1750-5-git-send-email-nhorman@tuxdriver.com>
Date:	Wed, 13 Oct 2010 22:01:52 -0400
From:	nhorman@...driver.com
To:	netdev@...r.kernel.org
Cc:	bonding-devel@...ts.sourceforge.net, fubar@...ibm.com,
	davem@...emloft.net, andy@...yhouse.net, amwang@...hat.com,
	nhorman@...driver.com
Subject: [PATCH 4/5] Fix netconsole to not deadlock on rmmod

From: Neil Horman <nhorman@...driver.com>

Netconsole calls netpoll_cleanup on receipt of a NETDEVICE_UNREGISTER event.
The notifier subsystem calls these event handlers with rtnl_lock held, which
netpoll_cleanup also takes, resulting in deadlock.  Fix this by calling the
__netpoll_cleanup interior function instead, and fixing up the additional
pointers.

Signed-off-by: Neil Horman <nhorman@...driver.com>
---
 drivers/net/netconsole.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index ca142c4..94255f0 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -678,7 +678,14 @@ static int netconsole_netdev_event(struct notifier_block *this,
 				strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
 				break;
 			case NETDEV_UNREGISTER:
-				netpoll_cleanup(&nt->np);
+				/*
+				 * rtnl_lock already held
+				 */
+				if (nt->np.dev) {
+					__netpoll_cleanup(&nt->np);
+					dev_put(nt->np.dev);
+					nt->np.dev = NULL;
+				}
 				/* Fall through */
 			case NETDEV_GOING_DOWN:
 			case NETDEV_BONDING_DESLAVE:
-- 
1.7.2.3

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