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author | Davide Caratti <dcaratti@redhat.com> | 2024-04-18 16:50:11 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-06-27 14:49:02 +0300 |
commit | 6d8b2c5206dd2f5136c8b5cb2292f502631b5e65 (patch) | |
tree | fc18557912278c1c49bbe054574b1ffbf923963c /net/sched | |
parent | 2f037b28a7bf3d29a1d71628049ce38c7f401eb6 (diff) | |
download | linux-6d8b2c5206dd2f5136c8b5cb2292f502631b5e65.tar.xz |
net/sched: fix false lockdep warning on qdisc root lock
[ Upstream commit af0cb3fa3f9ed258d14abab0152e28a0f9593084 ]
Xiumei and Christoph reported the following lockdep splat, complaining of
the qdisc root lock being taken twice:
============================================
WARNING: possible recursive locking detected
6.7.0-rc3+ #598 Not tainted
--------------------------------------------
swapper/2/0 is trying to acquire lock:
ffff888177190110 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1560/0x2e70
but task is already holding lock:
ffff88811995a110 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1560/0x2e70
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&sch->q.lock);
lock(&sch->q.lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
5 locks held by swapper/2/0:
#0: ffff888135a09d98 ((&in_dev->mr_ifc_timer)){+.-.}-{0:0}, at: call_timer_fn+0x11a/0x510
#1: ffffffffaaee5260 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x2c0/0x1ed0
#2: ffffffffaaee5200 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x209/0x2e70
#3: ffff88811995a110 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1560/0x2e70
#4: ffffffffaaee5200 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x209/0x2e70
stack backtrace:
CPU: 2 PID: 0 Comm: swapper/2 Not tainted 6.7.0-rc3+ #598
Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7353+9de0a3cc 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0x4a/0x80
__lock_acquire+0xfdd/0x3150
lock_acquire+0x1ca/0x540
_raw_spin_lock+0x34/0x80
__dev_queue_xmit+0x1560/0x2e70
tcf_mirred_act+0x82e/0x1260 [act_mirred]
tcf_action_exec+0x161/0x480
tcf_classify+0x689/0x1170
prio_enqueue+0x316/0x660 [sch_prio]
dev_qdisc_enqueue+0x46/0x220
__dev_queue_xmit+0x1615/0x2e70
ip_finish_output2+0x1218/0x1ed0
__ip_finish_output+0x8b3/0x1350
ip_output+0x163/0x4e0
igmp_ifc_timer_expire+0x44b/0x930
call_timer_fn+0x1a2/0x510
run_timer_softirq+0x54d/0x11a0
__do_softirq+0x1b3/0x88f
irq_exit_rcu+0x18f/0x1e0
sysvec_apic_timer_interrupt+0x6f/0x90
</IRQ>
This happens when TC does a mirred egress redirect from the root qdisc of
device A to the root qdisc of device B. As long as these two locks aren't
protecting the same qdisc, they can be acquired in chain: add a per-qdisc
lockdep key to silence false warnings.
This dynamic key should safely replace the static key we have in sch_htb:
it was added to allow enqueueing to the device "direct qdisc" while still
holding the qdisc root lock.
v2: don't use static keys anymore in HTB direct qdiscs (thanks Eric Dumazet)
CC: Maxim Mikityanskiy <maxim@isovalent.com>
CC: Xiumei Mu <xmu@redhat.com>
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/451
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/7dc06d6158f72053cf877a82e2a7a5bd23692faa.1713448007.git.dcaratti@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net/sched')
-rw-r--r-- | net/sched/sch_generic.c | 3 | ||||
-rw-r--r-- | net/sched/sch_htb.c | 22 |
2 files changed, 6 insertions, 19 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 5d7e23f4cc0e..bda9e473694b 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -942,7 +942,9 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, __skb_queue_head_init(&sch->gso_skb); __skb_queue_head_init(&sch->skb_bad_txq); gnet_stats_basic_sync_init(&sch->bstats); + lockdep_register_key(&sch->root_lock_key); spin_lock_init(&sch->q.lock); + lockdep_set_class(&sch->q.lock, &sch->root_lock_key); if (ops->static_flags & TCQ_F_CPUSTATS) { sch->cpu_bstats = @@ -1062,6 +1064,7 @@ static void __qdisc_destroy(struct Qdisc *qdisc) if (ops->destroy) ops->destroy(qdisc); + lockdep_unregister_key(&qdisc->root_lock_key); module_put(ops->owner); netdev_put(qdisc_dev(qdisc), &qdisc->dev_tracker); diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c index 0d947414e616..19035ef8387f 100644 --- a/net/sched/sch_htb.c +++ b/net/sched/sch_htb.c @@ -1039,13 +1039,6 @@ static void htb_work_func(struct work_struct *work) rcu_read_unlock(); } -static void htb_set_lockdep_class_child(struct Qdisc *q) -{ - static struct lock_class_key child_key; - - lockdep_set_class(qdisc_lock(q), &child_key); -} - static int htb_offload(struct net_device *dev, struct tc_htb_qopt_offload *opt) { return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_HTB, opt); @@ -1132,7 +1125,6 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt, return -ENOMEM; } - htb_set_lockdep_class_child(qdisc); q->direct_qdiscs[ntx] = qdisc; qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT; } @@ -1468,7 +1460,6 @@ static int htb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, } if (q->offload) { - htb_set_lockdep_class_child(new); /* One ref for cl->leaf.q, the other for dev_queue->qdisc. */ qdisc_refcount_inc(new); old_q = htb_graft_helper(dev_queue, new); @@ -1733,11 +1724,8 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg, new_q = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops, cl->parent->common.classid, NULL); - if (q->offload) { - if (new_q) - htb_set_lockdep_class_child(new_q); + if (q->offload) htb_parent_to_leaf_offload(sch, dev_queue, new_q); - } } sch_tree_lock(sch); @@ -1947,13 +1935,9 @@ static int htb_change_class(struct Qdisc *sch, u32 classid, new_q = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops, classid, NULL); if (q->offload) { - if (new_q) { - htb_set_lockdep_class_child(new_q); - /* One ref for cl->leaf.q, the other for - * dev_queue->qdisc. - */ + /* One ref for cl->leaf.q, the other for dev_queue->qdisc. */ + if (new_q) qdisc_refcount_inc(new_q); - } old_q = htb_graft_helper(dev_queue, new_q); /* No qdisc_put needed. */ WARN_ON(!(old_q->flags & TCQ_F_BUILTIN)); |