Commit 94833dfb authored Mar 20, 2008 by Jarek Poplawski Committed by David S. Miller Mar 20, 2008

[NET] ifb: set separate lockdep classes for queue locks



[   10.536424] =======================================================
[   10.536424] [ INFO: possible circular locking dependency detected ]
[   10.536424] 2.6.25-rc3-devel #3
[   10.536424] -------------------------------------------------------
[   10.536424] swapper/0 is trying to acquire lock:
[   10.536424]  (&dev->queue_lock){-+..}, at: [<c0299b4a>] 
dev_queue_xmit+0x175/0x2f3
[   10.536424]
[   10.536424] but task is already holding lock:
[   10.536424]  (&p->tcfc_lock){-+..}, at: [<f8a67154>] tcf_mirred+0x20/0x178 
[act_mirred]
[   10.536424]
[   10.536424] which lock already depends on the new lock.

lockdep warns of locking order while using ifb with sch_ingress and
act_mirred: ingress_lock, tcfc_lock, queue_lock (usually queue_lock
is at the beginning). This patch is only to tell lockdep that ifb is
a different device (e.g. from eth) and has its own pair of queue
locks. (This warning is a false-positive in common scenario of using
ifb; yet there are possible situations, when this order could be
dangerous; lockdep should warn in such a case.) (With suggestions by
David S. Miller)

Reported-and-tested-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 38fe999e

drivers/net/ifb.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -35,6 +35,7 @@
		#include <linux/moduleparam.h>
		#include <net/pkt_sched.h>
		#include <net/net_namespace.h>
		#include <linux/lockdep.h>

		#define TX_TIMEOUT (2*HZ)

		@@ -227,6 +228,16 @@ static struct rtnl_link_ops ifb_link_ops __read_mostly = {
		module_param(numifbs, int, 0);
		MODULE_PARM_DESC(numifbs, "Number of ifb devices");

		/*
		* dev_ifb->queue_lock is usually taken after dev->ingress_lock,
		* reversely to e.g. qdisc_lock_tree(). It should be safe until
		* ifb doesn't take dev->queue_lock with dev_ifb->ingress_lock.
		* But lockdep should know that ifb has different locks from dev.
		*/
		static struct lock_class_key ifb_queue_lock_key;
		static struct lock_class_key ifb_ingress_lock_key;


		static int __init ifb_init_one(int index)
		{
		struct net_device *dev_ifb;
		@@ -246,6 +257,10 @@ static int __init ifb_init_one(int index)
		err = register_netdevice(dev_ifb);
		if (err < 0)
		goto err;

		lockdep_set_class(&dev_ifb->queue_lock, &ifb_queue_lock_key);
		lockdep_set_class(&dev_ifb->ingress_lock, &ifb_ingress_lock_key);

		return 0;

		err:

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