linux-kernel - [ 04/49] netconsole: dont call __netpoll

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Message-Id: <20130326225840.029010040@linuxfoundation.org>
Date:	Tue, 26 Mar 2013 16:01:01 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Veaceslav Falico <vfalico@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 04/49] netconsole: dont call __netpoll_cleanup() while atomic

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Veaceslav Falico <vfalico@...hat.com>

[ Upstream commit 3f315bef23075ea8a98a6fe4221a83b83456d970 ]

__netpoll_cleanup() is called in netconsole_netdev_event() while holding a
spinlock. Release/acquire the spinlock before/after it and restart the
loop. Also, disable the netconsole completely, because we won't have chance
after the restart of the loop, and might end up in a situation where
nt->enabled == 1 and nt->np.dev == NULL.

Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
Acked-by: Neil Horman <nhorman@...driver.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/netconsole.c |   20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -630,6 +630,7 @@ static int netconsole_netdev_event(struc
 		goto done;
 
 	spin_lock_irqsave(&target_list_lock, flags);
+restart:
 	list_for_each_entry(nt, &target_list, list) {
 		netconsole_target_get(nt);
 		if (nt->np.dev == dev) {
@@ -642,20 +643,17 @@ static int netconsole_netdev_event(struc
 			case NETDEV_UNREGISTER:
 				/*
 				 * rtnl_lock already held
+				 * we might sleep in __netpoll_cleanup()
 				 */
-				if (nt->np.dev) {
-					spin_unlock_irqrestore(
-							      &target_list_lock,
-							      flags);
-					__netpoll_cleanup(&nt->np);
-					spin_lock_irqsave(&target_list_lock,
-							  flags);
-					dev_put(nt->np.dev);
-					nt->np.dev = NULL;
-				}
+				spin_unlock_irqrestore(&target_list_lock, flags);
+				__netpoll_cleanup(&nt->np);
+				spin_lock_irqsave(&target_list_lock, flags);
+				dev_put(nt->np.dev);
+				nt->np.dev = NULL;
 				nt->enabled = 0;
 				stopped = true;
-				break;
+				netconsole_target_put(nt);
+				goto restart;
 			}
 		}
 		netconsole_target_put(nt);


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