From 371fd83563252f550ce59476a7366d0b5171d316 Mon Sep 17 00:00:00 2001 From: Ulisses Furquim Date: Wed, 21 Dec 2011 20:02:36 -0200 Subject: Bluetooth: Fix deadlocks with sock lock and L2CAP timers locks 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: [] l2cap_chan_timeout+0x3c/0xe0 [bluetooth] but task is already holding lock: ((&(&chan->chan_timer)->work)){+.+...}, at: [] 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)){+.+...}: [] check_prevs_add+0xf6/0x170 [] validate_chain+0x613/0x790 [] __lock_acquire+0x4be/0xac0 [] lock_acquire+0x8d/0xb0 [] wait_on_work+0x4f/0x160 [] __cancel_work_timer+0x73/0x80 [] cancel_delayed_work_sync+0xd/0x10 [] l2cap_chan_connect+0x22d/0x470 [bluetooth] [] l2cap_sock_connect+0xb1/0x140 [bluetooth] [] kernel_connect+0xb/0x10 [] rfcomm_session_create+0x12a/0x1c0 [rfcomm] [] __rfcomm_dlc_open+0x1c7/0x240 [rfcomm] [] rfcomm_dlc_open+0x42/0x70 [rfcomm] [] rfcomm_sock_connect+0x103/0x150 [rfcomm] [] sys_connect+0xae/0xc0 [] compat_sys_socketcall+0xb2/0x220 [] sysenter_dispatch+0x7/0x30 -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}: [] check_prev_add+0x6cd/0x6e0 [] check_prevs_add+0xf6/0x170 [] validate_chain+0x613/0x790 [] __lock_acquire+0x4be/0xac0 [] lock_acquire+0x8d/0xb0 [] lock_sock_nested+0x8a/0xa0 [] l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [] process_one_work+0x184/0x450 [] worker_thread+0x15e/0x340 [] kthread+0x96/0xa0 [] 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: [] process_one_work+0x126/0x450 #1: ((&(&chan->chan_timer)->work)){+.+...}, at: [] process_one_work+0x126/0x450 stack backtrace: Pid: 873, comm: kworker/1:1 Not tainted 3.1.0-05270-ga978dc7-dirty #239 Call Trace: [] print_circular_bug+0xd2/0xe3 [] check_prev_add+0x6cd/0x6e0 [] check_prevs_add+0xf6/0x170 [] validate_chain+0x613/0x790 [] __lock_acquire+0x4be/0xac0 [] ? lock_sock_nested+0x66/0xa0 [] ? lock_release_nested+0x100/0x110 [] ? lock_sock_nested+0x66/0xa0 [] lock_acquire+0x8d/0xb0 [] ? l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [] lock_sock_nested+0x8a/0xa0 [] ? l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [] ? process_one_work+0x126/0x450 [] l2cap_chan_timeout+0x3c/0xe0 [bluetooth] [] process_one_work+0x184/0x450 [] ? process_one_work+0x126/0x450 [] ? l2cap_security_cfm+0x4e0/0x4e0 [bluetooth] [] worker_thread+0x15e/0x340 [] ? manage_workers+0x110/0x110 [] kthread+0x96/0xa0 [] kernel_thread_helper+0x4/0x10 [] ? retint_restore_args+0xe/0xe [] ? __init_kthread_worker+0x70/0x70 [] ? gs_change+0xb/0xb Signed-off-by: Ulisses Furquim Acked-by: Marcel Holtmann Signed-off-by: Gustavo F. Padovan --- include/net/bluetooth/l2cap.h | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) (limited to 'include/net') diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index f141fbecfa40..9572cbd12a7a 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -595,32 +595,45 @@ enum { FLAG_EFS_ENABLE, }; +static inline void l2cap_chan_hold(struct l2cap_chan *c) +{ + atomic_inc(&c->refcnt); +} + +static inline void l2cap_chan_put(struct l2cap_chan *c) +{ + if (atomic_dec_and_test(&c->refcnt)) + kfree(c); +} + static inline void l2cap_set_timer(struct l2cap_chan *chan, struct delayed_work *work, long timeout) { BT_DBG("chan %p state %d timeout %ld", chan, chan->state, timeout); - cancel_delayed_work_sync(work); - + if (!__cancel_delayed_work(work)) + l2cap_chan_hold(chan); schedule_delayed_work(work, timeout); } -static inline void l2cap_clear_timer(struct delayed_work *work) +static inline void l2cap_clear_timer(struct l2cap_chan *chan, + struct delayed_work *work) { - cancel_delayed_work_sync(work); + if (__cancel_delayed_work(work)) + l2cap_chan_put(chan); } #define __set_chan_timer(c, t) l2cap_set_timer(c, &c->chan_timer, (t)) -#define __clear_chan_timer(c) l2cap_clear_timer(&c->chan_timer) +#define __clear_chan_timer(c) l2cap_clear_timer(c, &c->chan_timer) #define __set_retrans_timer(c) l2cap_set_timer(c, &c->retrans_timer, \ L2CAP_DEFAULT_RETRANS_TO); -#define __clear_retrans_timer(c) l2cap_clear_timer(&c->retrans_timer) +#define __clear_retrans_timer(c) l2cap_clear_timer(c, &c->retrans_timer) #define __set_monitor_timer(c) l2cap_set_timer(c, &c->monitor_timer, \ L2CAP_DEFAULT_MONITOR_TO); -#define __clear_monitor_timer(c) l2cap_clear_timer(&c->monitor_timer) +#define __clear_monitor_timer(c) l2cap_clear_timer(c, &c->monitor_timer) #define __set_ack_timer(c) l2cap_set_timer(c, &chan->ack_timer, \ L2CAP_DEFAULT_ACK_TO); -#define __clear_ack_timer(c) l2cap_clear_timer(&c->ack_timer) +#define __clear_ack_timer(c) l2cap_clear_timer(c, &c->ack_timer) static inline int __seq_offset(struct l2cap_chan *chan, __u16 seq1, __u16 seq2) { -- cgit v1.2.3