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

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[   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>
This commit is contained in:
Jarek Poplawski 2008-03-20 17:05:13 -07:00 committed by David S. Miller
parent 38fe999e22
commit 94833dfb8c
1 changed files with 15 additions and 0 deletions
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15
drivers/net/ifb.c
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@ -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: