From 1905f6c736cb618e07eca0c96e60e3c024023428 Mon Sep 17 00:00:00 2001 From: Dave Young Date: Tue, 1 Apr 2008 23:59:06 -0700 Subject: bluetooth : __rfcomm_dlc_close lock fix Lockdep warning will be trigged while rfcomm connection closing. The locks taken in rfcomm_dev_add: rfcomm_dev_lock --> d->lock In __rfcomm_dlc_close: d->lock --> rfcomm_dev_lock (in rfcomm_dev_state_change) There's two way to fix it, one is in rfcomm_dev_add we first locking d->lock then the rfcomm_dev_lock The other (in this patch), remove the locking of d->lock for rfcomm_dev_state_change because just locking "d->state = BT_CLOSED;" is enough. [ 295.002046] ======================================================= [ 295.002046] [ INFO: possible circular locking dependency detected ] [ 295.002046] 2.6.25-rc7 #1 [ 295.002046] ------------------------------------------------------- [ 295.002046] krfcommd/2705 is trying to acquire lock: [ 295.002046] (rfcomm_dev_lock){-.--}, at: [] rfcomm_dev_state_change+0x6a/0xd0 [rfcomm] [ 295.002046] [ 295.002046] but task is already holding lock: [ 295.002046] (&d->lock){--..}, at: [] __rfcomm_dlc_close+0x43/0xd0 [rfcomm] [ 295.002046] [ 295.002046] which lock already depends on the new lock. [ 295.002046] [ 295.002046] [ 295.002046] the existing dependency chain (in reverse order) is: [ 295.002046] [ 295.002046] -> #1 (&d->lock){--..}: [ 295.002046] [] check_prev_add+0xd3/0x200 [ 295.002046] [] check_prevs_add+0x95/0xe0 [ 295.002046] [] validate_chain+0x23f/0x320 [ 295.002046] [] __lock_acquire+0x1c1/0x760 [ 295.002046] [] lock_acquire+0x79/0xb0 [ 295.002046] [] _spin_lock+0x39/0x80 [ 295.002046] [] rfcomm_dev_add+0x240/0x360 [rfcomm] [ 295.002046] [] rfcomm_create_dev+0x6e/0xe0 [rfcomm] [ 295.002046] [] rfcomm_dev_ioctl+0x33/0x60 [rfcomm] [ 295.002046] [] rfcomm_sock_ioctl+0x2c/0x50 [rfcomm] [ 295.002046] [] sock_ioctl+0x118/0x240 [ 295.002046] [] vfs_ioctl+0x76/0x90 [ 295.002046] [] do_vfs_ioctl+0x56/0x140 [ 295.002046] [] sys_ioctl+0x39/0x60 [ 295.002046] [] syscall_call+0x7/0xb [ 295.002046] [] 0xffffffff [ 295.002046] [ 295.002046] -> #0 (rfcomm_dev_lock){-.--}: [ 295.002046] [] check_prev_add+0x34/0x200 [ 295.002046] [] check_prevs_add+0x95/0xe0 [ 295.002046] [] validate_chain+0x23f/0x320 [ 295.002046] [] __lock_acquire+0x1c1/0x760 [ 295.002046] [] lock_acquire+0x79/0xb0 [ 295.002046] [] _read_lock+0x39/0x80 [ 295.002046] [] rfcomm_dev_state_change+0x6a/0xd0 [rfcomm] [ 295.002046] [] __rfcomm_dlc_close+0x58/0xd0 [rfcomm] [ 295.002046] [] rfcomm_recv_ua+0x6f/0x120 [rfcomm] [ 295.002046] [] rfcomm_recv_frame+0x171/0x1e0 [rfcomm] [ 295.002046] [] rfcomm_run+0xe7/0x550 [rfcomm] [ 295.002046] [] kthread+0x5c/0xa0 [ 295.002046] [] kernel_thread_helper+0x7/0x10 [ 295.002046] [] 0xffffffff [ 295.002046] [ 295.002046] other info that might help us debug this: [ 295.002046] [ 295.002046] 2 locks held by krfcommd/2705: [ 295.002046] #0: (rfcomm_mutex){--..}, at: [] rfcomm_run+0x7b/0x550 [rfcomm] [ 295.002046] #1: (&d->lock){--..}, at: [] __rfcomm_dlc_close+0x43/0xd0 [rfcomm] [ 295.002046] [ 295.002046] stack backtrace: [ 295.002046] Pid: 2705, comm: krfcommd Not tainted 2.6.25-rc7 #1 [ 295.002046] [] ? printk+0x18/0x20 [ 295.002046] [] print_circular_bug_tail+0x6f/0x80 [ 295.002046] [] check_prev_add+0x34/0x200 [ 295.002046] [] check_prevs_add+0x95/0xe0 [ 295.002046] [] validate_chain+0x23f/0x320 [ 295.002046] [] __lock_acquire+0x1c1/0x760 [ 295.002046] [] lock_acquire+0x79/0xb0 [ 295.002046] [] ? rfcomm_dev_state_change+0x6a/0xd0 [rfcomm] [ 295.002046] [] _read_lock+0x39/0x80 [ 295.002046] [] ? rfcomm_dev_state_change+0x6a/0xd0 [rfcomm] [ 295.002046] [] rfcomm_dev_state_change+0x6a/0xd0 [rfcomm] [ 295.002046] [] __rfcomm_dlc_close+0x58/0xd0 [rfcomm] [ 295.002046] [] rfcomm_recv_ua+0x6f/0x120 [rfcomm] [ 295.002046] [] rfcomm_recv_frame+0x171/0x1e0 [rfcomm] [ 295.002046] [] ? trace_hardirqs_on+0xb9/0x130 [ 295.002046] [] ? _spin_unlock_irqrestore+0x39/0x70 [ 295.002046] [] rfcomm_run+0xe7/0x550 [rfcomm] [ 295.002046] [] ? __sched_text_start+0x229/0x4c0 [ 295.002046] [] ? cpu_avg_load_per_task+0x20/0x30 [ 295.002046] [] ? rfcomm_run+0x0/0x550 [rfcomm] [ 295.002046] [] kthread+0x5c/0xa0 [ 295.002046] [] ? kthread+0x0/0xa0 [ 295.002046] [] kernel_thread_helper+0x7/0x10 [ 295.002046] ======================= Signed-off-by: Dave Young Signed-off-by: David S. Miller --- net/bluetooth/rfcomm/tty.c | 5 ----- 1 file changed, 5 deletions(-) (limited to 'net/bluetooth/rfcomm/tty.c') diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c index e4c779bb8d76..c3f749abb2d0 100644 --- a/net/bluetooth/rfcomm/tty.c +++ b/net/bluetooth/rfcomm/tty.c @@ -570,12 +570,7 @@ static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err) return; rfcomm_dev_del(dev); - /* We have to drop DLC lock here, otherwise - rfcomm_dev_put() will dead lock if it's - the last reference. */ - rfcomm_dlc_unlock(dlc); rfcomm_dev_put(dev); - rfcomm_dlc_lock(dlc); } } else tty_hangup(dev->tty); -- cgit v1.2.3