From 23d3b8bfb8eb20e7d96afa09991e6a5ed1c83164 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 5 Sep 2012 01:02:56 +0000 Subject: net: qdisc busylock needs lockdep annotations It seems we need to provide ability for stacked devices to use specific lock_class_key for sch->busylock We could instead default l2tpeth tx_queue_len to 0 (no qdisc), but a user might use a qdisc anyway. (So same fixes are probably needed on non LLTX stacked drivers) Noticed while stressing L2TPV3 setup : ====================================================== [ INFO: possible circular locking dependency detected ] 3.6.0-rc3+ #788 Not tainted ------------------------------------------------------- netperf/4660 is trying to acquire lock: (l2tpsock){+.-...}, at: [] l2tp_xmit_skb+0x172/0xa50 [l2tp_core] but task is already holding lock: (&(&sch->busylock)->rlock){+.-...}, at: [] dev_queue_xmit+0xd75/0xe00 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&(&sch->busylock)->rlock){+.-...}: [] lock_acquire+0x90/0x200 [] _raw_spin_lock_irqsave+0x4c/0x60 [] __wake_up+0x32/0x70 [] tty_wakeup+0x3e/0x80 [] pty_write+0x73/0x80 [] tty_put_char+0x3c/0x40 [] process_echoes+0x142/0x330 [] n_tty_receive_buf+0x8fb/0x1230 [] flush_to_ldisc+0x142/0x1c0 [] process_one_work+0x198/0x760 [] worker_thread+0x186/0x4b0 [] kthread+0x93/0xa0 [] kernel_thread_helper+0x4/0x10 -> #0 (l2tpsock){+.-...}: [] __lock_acquire+0x1628/0x1b10 [] lock_acquire+0x90/0x200 [] _raw_spin_lock+0x41/0x50 [] l2tp_xmit_skb+0x172/0xa50 [l2tp_core] [] l2tp_eth_dev_xmit+0x32/0x60 [l2tp_eth] [] dev_hard_start_xmit+0x502/0xa70 [] sch_direct_xmit+0xfe/0x290 [] dev_queue_xmit+0x1e5/0xe00 [] ip_finish_output+0x3d0/0x890 [] ip_output+0x59/0xf0 [] ip_local_out+0x2d/0xa0 [] ip_queue_xmit+0x1c3/0x680 [] tcp_transmit_skb+0x402/0xa60 [] tcp_write_xmit+0x1f4/0xa30 [] tcp_push_one+0x30/0x40 [] tcp_sendmsg+0xe82/0x1040 [] inet_sendmsg+0x125/0x230 [] sock_sendmsg+0xdc/0xf0 [] sys_sendto+0xfe/0x130 [] system_call_fastpath+0x16/0x1b Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&sch->busylock)->rlock); lock(l2tpsock); lock(&(&sch->busylock)->rlock); lock(l2tpsock); *** DEADLOCK *** 5 locks held by netperf/4660: #0: (sk_lock-AF_INET){+.+.+.}, at: [] tcp_sendmsg+0x2c/0x1040 #1: (rcu_read_lock){.+.+..}, at: [] ip_queue_xmit+0x0/0x680 #2: (rcu_read_lock_bh){.+....}, at: [] ip_finish_output+0x135/0x890 #3: (rcu_read_lock_bh){.+....}, at: [] dev_queue_xmit+0x0/0xe00 #4: (&(&sch->busylock)->rlock){+.-...}, at: [] dev_queue_xmit+0xd75/0xe00 stack backtrace: Pid: 4660, comm: netperf Not tainted 3.6.0-rc3+ #788 Call Trace: [] print_circular_bug+0x1fb/0x20c [] __lock_acquire+0x1628/0x1b10 [] ? check_usage+0x9b/0x4d0 [] ? __lock_acquire+0x2e4/0x1b10 [] lock_acquire+0x90/0x200 [] ? l2tp_xmit_skb+0x172/0xa50 [l2tp_core] [] _raw_spin_lock+0x41/0x50 [] ? l2tp_xmit_skb+0x172/0xa50 [l2tp_core] [] l2tp_xmit_skb+0x172/0xa50 [l2tp_core] [] l2tp_eth_dev_xmit+0x32/0x60 [l2tp_eth] [] dev_hard_start_xmit+0x502/0xa70 [] ? dev_hard_start_xmit+0x5e/0xa70 [] ? dev_queue_xmit+0x141/0xe00 [] sch_direct_xmit+0xfe/0x290 [] dev_queue_xmit+0x1e5/0xe00 [] ? dev_hard_start_xmit+0xa70/0xa70 [] ip_finish_output+0x3d0/0x890 [] ? ip_finish_output+0x135/0x890 [] ip_output+0x59/0xf0 [] ip_local_out+0x2d/0xa0 [] ip_queue_xmit+0x1c3/0x680 [] ? ip_local_out+0xa0/0xa0 [] tcp_transmit_skb+0x402/0xa60 [] ? tcp_md5_do_lookup+0x18e/0x1a0 [] tcp_write_xmit+0x1f4/0xa30 [] tcp_push_one+0x30/0x40 [] tcp_sendmsg+0xe82/0x1040 [] inet_sendmsg+0x125/0x230 [] ? inet_create+0x6b0/0x6b0 [] ? sock_update_classid+0xc2/0x3b0 [] ? sock_update_classid+0x130/0x3b0 [] sock_sendmsg+0xdc/0xf0 [] ? fget_light+0x3f9/0x4f0 [] sys_sendto+0xfe/0x130 [] ? trace_hardirqs_on+0xd/0x10 [] ? _raw_spin_unlock_irq+0x30/0x50 [] ? finish_task_switch+0x83/0xf0 [] ? finish_task_switch+0x46/0xf0 [] ? sysret_check+0x1b/0x56 [] system_call_fastpath+0x16/0x1b Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/sched/sch_generic.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'net/sched') diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 6c4d5fe53ce8..aefc1504dc88 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -527,6 +527,8 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = { }; EXPORT_SYMBOL(pfifo_fast_ops); +static struct lock_class_key qdisc_tx_busylock; + struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, struct Qdisc_ops *ops) { @@ -534,6 +536,7 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, struct Qdisc *sch; unsigned int size = QDISC_ALIGN(sizeof(*sch)) + ops->priv_size; int err = -ENOBUFS; + struct net_device *dev = dev_queue->dev; p = kzalloc_node(size, GFP_KERNEL, netdev_queue_numa_node_read(dev_queue)); @@ -553,12 +556,16 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, } INIT_LIST_HEAD(&sch->list); skb_queue_head_init(&sch->q); + spin_lock_init(&sch->busylock); + lockdep_set_class(&sch->busylock, + dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); + sch->ops = ops; sch->enqueue = ops->enqueue; sch->dequeue = ops->dequeue; sch->dev_queue = dev_queue; - dev_hold(qdisc_dev(sch)); + dev_hold(dev); atomic_set(&sch->refcnt, 1); return sch; -- cgit v1.2.3