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When cancelling a delayed work (timer) in L2CAP we can not sleep holding the sock mutex otherwise we might deadlock with an L2CAP timer handler. This is possible because RX/TX and L2CAP timers run in different workqueues. The scenario below illustrates the problem. Thus we are now avoiding to sleep on the timers locks. ====================================================== [ INFO: possible circular locking dependency detected ] 3.1.0-05270-ga978dc7-dirty #239 ------------------------------------------------------- kworker/1:1/873 is trying to acquire lock: (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}, at: [<ffffffffa002ceac>] l2cap_chan_timeout+0x3c/0xe0 [bluetooth] but task is already holding lock: ((&(&chan->chan_timer)->work)){+.+...}, at: [<ffffffff81051a86>] process_one_work+0x126/0x450 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 ((&(&chan->chan_timer)->work)){+.+...}: [<ffffffff8106b276>] check_prevs_add+0xf6/0x170 [<ffffffff8106b903>] validate_chain+0x613/0x790 [<ffffffff8106dfee>] __lock_acquire+0x4be/0xac0 [<ffffffff8106ec2d>] lock_acquire+0x8d/0xb0 [<ffffffff81052a6f>] wait_on_work+0x4f/0x160 [<ffffffff81052ca3>] __cancel_work_timer+0x73/0x80 [<ffffffff81052cbd>] cancel_delayed_work_sync+0xd/0x10 [<ffffffffa002f2ed>] l2cap_chan_connect+0x22d/0x470 [bluetooth] [<ffffffffa002fb51>] l2cap_sock_connect+0xb1/0x140 [bluetooth] [<ffffffff8130811b>] kernel_connect+0xb/0x10 [<ffffffffa00cf98a>] rfcomm_session_create+0x12a/0x1c0 [rfcomm] [<ffffffffa00cfbe7>] __rfcomm_dlc_open+0x1c7/0x240 [rfcomm] [<ffffffffa00d07c2>] rfcomm_dlc_open+0x42/0x70 [rfcomm] [<ffffffffa00d3b03>] rfcomm_sock_connect+0x103/0x150 [rfcomm] [<ffffffff8130bd7e>] sys_connect+0xae/0xc0 [<ffffffff813368d2>] compat_sys_socketcall+0xb2/0x220 [<ffffffff813b2089>] sysenter_dispatch+0x7/0x30 -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}: [<ffffffff8106b16d>] check_prev_add+0x6cd/0x6e0 [<ffffffff8106b276>] check_prevs_add+0xf6/0x170 [<ffffffff8106b903>] validate_chain+0x613/0x790 [<ffffffff8106dfee>] __lock_acquire+0x4be/0xac0 [<ffffffff8106ec2d>] lock_acquire+0x8d/0xb0 [<ffffffff8130d91a>] lock_sock_nested+0x8a/0xa0 [<ffffffffa002ceac>] l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [<ffffffff81051ae4>] process_one_work+0x184/0x450 [<ffffffff8105276e>] worker_thread+0x15e/0x340 [<ffffffff81057bb6>] kthread+0x96/0xa0 [<ffffffff813b1ef4>] kernel_thread_helper+0x4/0x10 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((&(&chan->chan_timer)->work)); lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP); lock((&(&chan->chan_timer)->work)); lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP); *** DEADLOCK *** 2 locks held by kworker/1:1/873: #0: (events){.+.+.+}, at: [<ffffffff81051a86>] process_one_work+0x126/0x450 #1: ((&(&chan->chan_timer)->work)){+.+...}, at: [<ffffffff81051a86>] process_one_work+0x126/0x450 stack backtrace: Pid: 873, comm: kworker/1:1 Not tainted 3.1.0-05270-ga978dc7-dirty #239 Call Trace: [<ffffffff813a0f6e>] print_circular_bug+0xd2/0xe3 [<ffffffff8106b16d>] check_prev_add+0x6cd/0x6e0 [<ffffffff8106b276>] check_prevs_add+0xf6/0x170 [<ffffffff8106b903>] validate_chain+0x613/0x790 [<ffffffff8106dfee>] __lock_acquire+0x4be/0xac0 [<ffffffff8130d8f6>] ? lock_sock_nested+0x66/0xa0 [<ffffffff8106ea30>] ? lock_release_nested+0x100/0x110 [<ffffffff8130d8f6>] ? lock_sock_nested+0x66/0xa0 [<ffffffff8106ec2d>] lock_acquire+0x8d/0xb0 [<ffffffffa002ceac>] ? l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [<ffffffff8130d91a>] lock_sock_nested+0x8a/0xa0 [<ffffffffa002ceac>] ? l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [<ffffffff81051a86>] ? process_one_work+0x126/0x450 [<ffffffffa002ceac>] l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [<ffffffff81051ae4>] process_one_work+0x184/0x450 [<ffffffff81051a86>] ? process_one_work+0x126/0x450 [<ffffffffa002ce70>] ? l2cap_security_cfm+0x4e0/0x4e0 [bluetooth] [<ffffffff8105276e>] worker_thread+0x15e/0x340 [<ffffffff81052610>] ? manage_workers+0x110/0x110 [<ffffffff81057bb6>] kthread+0x96/0xa0 [<ffffffff813b1ef4>] kernel_thread_helper+0x4/0x10 [<ffffffff813af69d>] ? retint_restore_args+0xe/0xe [<ffffffff81057b20>] ? __init_kthread_worker+0x70/0x70 [<ffffffff813b1ef0>] ? gs_change+0xb/0xb Signed-off-by: Ulisses Furquim <ulisses@profusion.mobi> Acked-by: Marcel Holtmann <marcel@holtmann.org> Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi> |
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| 9p | ||
| bluetooth | ||
| caif | ||
| irda | ||
| iucv | ||
| netfilter | ||
| netns | ||
| nfc | ||
| phonet | ||
| sctp | ||
| tc_act | ||
| act_api.h | ||
| addrconf.h | ||
| af_ieee802154.h | ||
| af_rxrpc.h | ||
| af_unix.h | ||
| ah.h | ||
| arp.h | ||
| atmclip.h | ||
| ax25.h | ||
| ax88796.h | ||
| cfg80211-wext.h | ||
| cfg80211.h | ||
| checksum.h | ||
| cipso_ipv4.h | ||
| cls_cgroup.h | ||
| compat.h | ||
| datalink.h | ||
| dcbevent.h | ||
| dcbnl.h | ||
| dn_dev.h | ||
| dn_fib.h | ||
| dn_neigh.h | ||
| dn_nsp.h | ||
| dn_route.h | ||
| dn.h | ||
| dsa.h | ||
| dsfield.h | ||
| dst_ops.h | ||
| dst.h | ||
| esp.h | ||
| ethoc.h | ||
| fib_rules.h | ||
| flow.h | ||
| garp.h | ||
| gen_stats.h | ||
| genetlink.h | ||
| gre.h | ||
| icmp.h | ||
| ieee80211_radiotap.h | ||
| ieee802154_netdev.h | ||
| ieee802154.h | ||
| if_inet6.h | ||
| inet6_connection_sock.h | ||
| inet6_hashtables.h | ||
| inet_common.h | ||
| inet_connection_sock.h | ||
| inet_ecn.h | ||
| inet_frag.h | ||
| inet_hashtables.h | ||
| inet_sock.h | ||
| inet_timewait_sock.h | ||
| inetpeer.h | ||
| ip6_checksum.h | ||
| ip6_fib.h | ||
| ip6_route.h | ||
| ip6_tunnel.h | ||
| ip_fib.h | ||
| ip_vs.h | ||
| ip.h | ||
| ipcomp.h | ||
| ipconfig.h | ||
| ipip.h | ||
| ipv6.h | ||
| ipx.h | ||
| iw_handler.h | ||
| lapb.h | ||
| lib80211.h | ||
| llc_c_ac.h | ||
| llc_c_ev.h | ||
| llc_c_st.h | ||
| llc_conn.h | ||
| llc_if.h | ||
| llc_pdu.h | ||
| llc_s_ac.h | ||
| llc_s_ev.h | ||
| llc_s_st.h | ||
| llc_sap.h | ||
| llc.h | ||
| mac80211.h | ||
| mip6.h | ||
| mld.h | ||
| ndisc.h | ||
| neighbour.h | ||
| net_namespace.h | ||
| net_ratelimit.h | ||
| netdma.h | ||
| netevent.h | ||
| netlabel.h | ||
| netlink.h | ||
| netrom.h | ||
| nexthop.h | ||
| nl802154.h | ||
| p8022.h | ||
| ping.h | ||
| pkt_cls.h | ||
| pkt_sched.h | ||
| protocol.h | ||
| psnap.h | ||
| raw.h | ||
| rawv6.h | ||
| red.h | ||
| regulatory.h | ||
| request_sock.h | ||
| rose.h | ||
| route.h | ||
| rtnetlink.h | ||
| sch_generic.h | ||
| scm.h | ||
| secure_seq.h | ||
| slhc_vj.h | ||
| snmp.h | ||
| sock.h | ||
| stp.h | ||
| tcp_states.h | ||
| tcp.h | ||
| timewait_sock.h | ||
| transp_v6.h | ||
| udp.h | ||
| udplite.h | ||
| wext.h | ||
| wimax.h | ||
| wpan-phy.h | ||
| x25.h | ||
| x25device.h | ||
| xfrm.h | ||