Commits
Vlad Buslov committed c2999f7fb05
net: sched: multiq: don't call qdisc_put() while holding tree lock
Recent changes that removed rtnl dependency from rules update path of tc
also made tcf_block_put() function sleeping. This function is called from
ops->destroy() of several Qdisc implementations, which in turn is called by
qdisc_put(). Some Qdiscs call qdisc_put() while holding sch tree spinlock,
which results sleeping-while-atomic BUG.
Steps to reproduce for multiq:
tc qdisc add dev ens1f0 root handle 1: multiq
tc qdisc add dev ens1f0 parent 1:10 handle 50: sfq perturb 10
ethtool -L ens1f0 combined 2
tc qdisc change dev ens1f0 root handle 1: multiq
Resulting dmesg:
[ 5539.419344] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:909
[ 5539.420945] in_atomic(): 1, irqs_disabled(): 0, pid: 27658, name: tc
[ 5539.422435] INFO: lockdep is turned off.
[ 5539.423904] CPU: 21 PID: 27658 Comm: tc Tainted: G W 5.3.0-rc8+ #721
[ 5539.425400] Hardware name: Supermicro SYS-2028TP-DECR/X10DRT-P, BIOS 2.0b 03/30/2017
[ 5539.426911] Call Trace:
[ 5539.428380] dump_stack+0x85/0xc0
[ 5539.429823] ___might_sleep.cold+0xac/0xbc
[ 5539.431262] __mutex_lock+0x5b/0x960
[ 5539.432682] ? tcf_chain0_head_change_cb_del.isra.0+0x1b/0xf0
[ 5539.434103] ? __nla_validate_parse+0x51/0x840
[ 5539.435493] ? tcf_chain0_head_change_cb_del.isra.0+0x1b/0xf0
[ 5539.436903] tcf_chain0_head_change_cb_del.isra.0+0x1b/0xf0
[ 5539.438327] tcf_block_put_ext.part.0+0x21/0x50
[ 5539.439752] tcf_block_put+0x50/0x70
[ 5539.441165] sfq_destroy+0x15/0x50 [sch_sfq]
[ 5539.442570] qdisc_destroy+0x5f/0x160
[ 5539.444000] multiq_tune+0x14a/0x420 [sch_multiq]
[ 5539.445421] tc_modify_qdisc+0x324/0x840
[ 5539.446841] rtnetlink_rcv_msg+0x170/0x4b0
[ 5539.448269] ? netlink_deliver_tap+0x95/0x400
[ 5539.449691] ? rtnl_dellink+0x2d0/0x2d0
[ 5539.451116] netlink_rcv_skb+0x49/0x110
[ 5539.452522] netlink_unicast+0x171/0x200
[ 5539.453914] netlink_sendmsg+0x224/0x3f0
[ 5539.455304] sock_sendmsg+0x5e/0x60
[ 5539.456686] ___sys_sendmsg+0x2ae/0x330
[ 5539.458071] ? ___sys_recvmsg+0x159/0x1f0
[ 5539.459461] ? do_wp_page+0x9c/0x790
[ 5539.460846] ? __handle_mm_fault+0xcd3/0x19e0
[ 5539.462263] __sys_sendmsg+0x59/0xa0
[ 5539.463661] do_syscall_64+0x5c/0xb0
[ 5539.465044] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 5539.466454] RIP: 0033:0x7f1fe08177b8
[ 5539.467863] Code: 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 65 8f 0c 00 8b 00 85 c0 75 17 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 89 5
4
[ 5539.470906] RSP: 002b:00007ffe812de5d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[ 5539.472483] RAX: ffffffffffffffda RBX: 000000005d8135e3 RCX: 00007f1fe08177b8
[ 5539.474069] RDX: 0000000000000000 RSI: 00007ffe812de640 RDI: 0000000000000003
[ 5539.475655] RBP: 0000000000000000 R08: 0000000000000001 R09: 000000000182e9b0
[ 5539.477203] R10: 0000000000404eda R11: 0000000000000246 R12: 0000000000000001
[ 5539.478699] R13: 000000000047f640 R14: 0000000000000000 R15: 0000000000000000
Rearrange locking in multiq_tune() in following ways:
- In loop that removes Qdiscs from disabled queues, call
qdisc_purge_queue() instead of qdisc_tree_flush_backlog() on Qdisc that
is being destroyed. Save the Qdisc in temporary allocated array and call
qdisc_put() on each element of the array after sch tree lock is released.
This is safe to do because Qdiscs have already been reset by
qdisc_purge_queue() inside sch tree lock critical section.
- Do the same change for second loop that initializes Qdiscs for newly
enabled queues in multiq_tune() function. Since sch tree lock is obtained
and released on each iteration of this loop, just call qdisc_put()
directly outside of critical section. Don't verify that old Qdisc is not
noop_qdisc before releasing reference to it because such check is already
performed by qdisc_put*() functions.
Fixes: c266f64dbfa2 ("net: sched: protect block state with mutex")
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>