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Date: Wed, 05 Sep 2012 13:02:56 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] net: qdisc busylock needs lockdep annotations
From: Eric Dumazet <edumazet@...gle.com>
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: [<ffffffffa0208db2>] l2tp_xmit_skb+0x172/0xa50 [l2tp_core]
but task is already holding lock:
(&(&sch->busylock)->rlock){+.-...}, at: [<ffffffff81596595>] 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){+.-...}:
[<ffffffff810a5df0>] lock_acquire+0x90/0x200
[<ffffffff817499fc>] _raw_spin_lock_irqsave+0x4c/0x60
[<ffffffff81074872>] __wake_up+0x32/0x70
[<ffffffff8136d39e>] tty_wakeup+0x3e/0x80
[<ffffffff81378fb3>] pty_write+0x73/0x80
[<ffffffff8136cb4c>] tty_put_char+0x3c/0x40
[<ffffffff813722b2>] process_echoes+0x142/0x330
[<ffffffff813742ab>] n_tty_receive_buf+0x8fb/0x1230
[<ffffffff813777b2>] flush_to_ldisc+0x142/0x1c0
[<ffffffff81062818>] process_one_work+0x198/0x760
[<ffffffff81063236>] worker_thread+0x186/0x4b0
[<ffffffff810694d3>] kthread+0x93/0xa0
[<ffffffff81753e24>] kernel_thread_helper+0x4/0x10
-> #0 (l2tpsock){+.-...}:
[<ffffffff810a5288>] __lock_acquire+0x1628/0x1b10
[<ffffffff810a5df0>] lock_acquire+0x90/0x200
[<ffffffff817498c1>] _raw_spin_lock+0x41/0x50
[<ffffffffa0208db2>] l2tp_xmit_skb+0x172/0xa50 [l2tp_core]
[<ffffffffa021a802>] l2tp_eth_dev_xmit+0x32/0x60 [l2tp_eth]
[<ffffffff815952b2>] dev_hard_start_xmit+0x502/0xa70
[<ffffffff815b63ce>] sch_direct_xmit+0xfe/0x290
[<ffffffff81595a05>] dev_queue_xmit+0x1e5/0xe00
[<ffffffff815d9d60>] ip_finish_output+0x3d0/0x890
[<ffffffff815db019>] ip_output+0x59/0xf0
[<ffffffff815da36d>] ip_local_out+0x2d/0xa0
[<ffffffff815da5a3>] ip_queue_xmit+0x1c3/0x680
[<ffffffff815f4192>] tcp_transmit_skb+0x402/0xa60
[<ffffffff815f4a94>] tcp_write_xmit+0x1f4/0xa30
[<ffffffff815f5300>] tcp_push_one+0x30/0x40
[<ffffffff815e6672>] tcp_sendmsg+0xe82/0x1040
[<ffffffff81614495>] inet_sendmsg+0x125/0x230
[<ffffffff81576cdc>] sock_sendmsg+0xdc/0xf0
[<ffffffff81579ece>] sys_sendto+0xfe/0x130
[<ffffffff81752c92>] 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: [<ffffffff815e581c>] tcp_sendmsg+0x2c/0x1040
#1: (rcu_read_lock){.+.+..}, at: [<ffffffff815da3e0>] ip_queue_xmit+0x0/0x680
#2: (rcu_read_lock_bh){.+....}, at: [<ffffffff815d9ac5>] ip_finish_output+0x135/0x890
#3: (rcu_read_lock_bh){.+....}, at: [<ffffffff81595820>] dev_queue_xmit+0x0/0xe00
#4: (&(&sch->busylock)->rlock){+.-...}, at: [<ffffffff81596595>] dev_queue_xmit+0xd75/0xe00
stack backtrace:
Pid: 4660, comm: netperf Not tainted 3.6.0-rc3+ #788
Call Trace:
[<ffffffff8173dbf8>] print_circular_bug+0x1fb/0x20c
[<ffffffff810a5288>] __lock_acquire+0x1628/0x1b10
[<ffffffff810a334b>] ? check_usage+0x9b/0x4d0
[<ffffffff810a3f44>] ? __lock_acquire+0x2e4/0x1b10
[<ffffffff810a5df0>] lock_acquire+0x90/0x200
[<ffffffffa0208db2>] ? l2tp_xmit_skb+0x172/0xa50 [l2tp_core]
[<ffffffff817498c1>] _raw_spin_lock+0x41/0x50
[<ffffffffa0208db2>] ? l2tp_xmit_skb+0x172/0xa50 [l2tp_core]
[<ffffffffa0208db2>] l2tp_xmit_skb+0x172/0xa50 [l2tp_core]
[<ffffffffa021a802>] l2tp_eth_dev_xmit+0x32/0x60 [l2tp_eth]
[<ffffffff815952b2>] dev_hard_start_xmit+0x502/0xa70
[<ffffffff81594e0e>] ? dev_hard_start_xmit+0x5e/0xa70
[<ffffffff81595961>] ? dev_queue_xmit+0x141/0xe00
[<ffffffff815b63ce>] sch_direct_xmit+0xfe/0x290
[<ffffffff81595a05>] dev_queue_xmit+0x1e5/0xe00
[<ffffffff81595820>] ? dev_hard_start_xmit+0xa70/0xa70
[<ffffffff815d9d60>] ip_finish_output+0x3d0/0x890
[<ffffffff815d9ac5>] ? ip_finish_output+0x135/0x890
[<ffffffff815db019>] ip_output+0x59/0xf0
[<ffffffff815da36d>] ip_local_out+0x2d/0xa0
[<ffffffff815da5a3>] ip_queue_xmit+0x1c3/0x680
[<ffffffff815da3e0>] ? ip_local_out+0xa0/0xa0
[<ffffffff815f4192>] tcp_transmit_skb+0x402/0xa60
[<ffffffff815fa25e>] ? tcp_md5_do_lookup+0x18e/0x1a0
[<ffffffff815f4a94>] tcp_write_xmit+0x1f4/0xa30
[<ffffffff815f5300>] tcp_push_one+0x30/0x40
[<ffffffff815e6672>] tcp_sendmsg+0xe82/0x1040
[<ffffffff81614495>] inet_sendmsg+0x125/0x230
[<ffffffff81614370>] ? inet_create+0x6b0/0x6b0
[<ffffffff8157e6e2>] ? sock_update_classid+0xc2/0x3b0
[<ffffffff8157e750>] ? sock_update_classid+0x130/0x3b0
[<ffffffff81576cdc>] sock_sendmsg+0xdc/0xf0
[<ffffffff81162579>] ? fget_light+0x3f9/0x4f0
[<ffffffff81579ece>] sys_sendto+0xfe/0x130
[<ffffffff810a69ad>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff8174a0b0>] ? _raw_spin_unlock_irq+0x30/0x50
[<ffffffff810757e3>] ? finish_task_switch+0x83/0xf0
[<ffffffff810757a6>] ? finish_task_switch+0x46/0xf0
[<ffffffff81752cb7>] ? sysret_check+0x1b/0x56
[<ffffffff81752c92>] system_call_fastpath+0x16/0x1b
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/netdevice.h | 2 ++
net/l2tp/l2tp_eth.c | 3 ++-
net/sched/sch_generic.c | 9 ++++++++-
3 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ccac82e..ae3153c0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1322,6 +1322,8 @@ struct net_device {
/* phy device may attach itself for hardware timestamping */
struct phy_device *phydev;
+ struct lock_class_key *qdisc_tx_busylock;
+
/* group the device belongs to */
int group;
diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
index f9ee74d..37b8b8b 100644
--- a/net/l2tp/l2tp_eth.c
+++ b/net/l2tp/l2tp_eth.c
@@ -67,6 +67,7 @@ static inline struct l2tp_eth_net *l2tp_eth_pernet(struct net *net)
return net_generic(net, l2tp_eth_net_id);
}
+static struct lock_class_key l2tp_eth_tx_busylock;
static int l2tp_eth_dev_init(struct net_device *dev)
{
struct l2tp_eth *priv = netdev_priv(dev);
@@ -74,7 +75,7 @@ static int l2tp_eth_dev_init(struct net_device *dev)
priv->dev = dev;
eth_hw_addr_random(dev);
memset(&dev->broadcast[0], 0xff, 6);
-
+ dev->qdisc_tx_busylock = &l2tp_eth_tx_busylock;
return 0;
}
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 6c4d5fe..aefc150 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;
--
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