From: Jarek Poplawski Date: Fri, 21 Mar 2008 00:05:13 +0000 (-0700) Subject: [NET] ifb: set separate lockdep classes for queue locks X-Git-Tag: v2.6.25-rc7~54^2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=94833dfb8c98ed4ca1944dd2c1339d88a2d1c758;p=linux-2.6 [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: [] dev_queue_xmit+0x175/0x2f3 [ 10.536424] [ 10.536424] but task is already holding lock: [ 10.536424] (&p->tcfc_lock){-+..}, at: [] 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 Signed-off-by: Jarek Poplawski Acked-by: Jamal Hadi Salim Signed-off-by: David S. Miller --- diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c index 15949d3df1..af233b5915 100644 --- a/drivers/net/ifb.c +++ b/drivers/net/ifb.c @@ -35,6 +35,7 @@ #include #include #include +#include #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: