tty related lockdep trace during bootup on 3.2-rc2

From: Dave Jones
Date: Tue Nov 22 2011 - 22:38:54 EST

>From Linus' current tree...

related to 5dc2470c602da8851907ec18942cd876c3b4ecc1 maybe ?

Dave

[ 40.778011] ======================================================
[ 40.780010] [ INFO: possible circular locking dependency detected ]
[ 40.780010] 3.2.0-rc2+ #8
[ 40.780010] -------------------------------------------------------
[ 40.780010] modem-manager/1141 is trying to acquire lock:
[ 40.780010] (big_tty_mutex){+.+.+.}, at: [<ffffffff81682807>] tty_lock+0x17/0x19
[ 40.780010]
[ 40.780010] but task is already holding lock:
[ 40.780010] (open_mutex){+.+...}, at: [<ffffffffa032b321>] acm_tty_close+0x41/0xc0 [cdc_acm]
[ 40.780010]
[ 40.780010] which lock already depends on the new lock.
[ 40.780010]
[ 40.780010]
[ 40.780010] the existing dependency chain (in reverse order) is:
[ 40.780010]
[ 40.780010] -> #1 (open_mutex){+.+...}:
[ 40.780010] [<ffffffff810c1d9d>] lock_acquire+0x9d/0x210
[ 40.780010] [<ffffffff8168003e>] __mutex_lock_common+0x5e/0x4f0
[ 40.780010] [<ffffffff81680604>] mutex_lock_nested+0x44/0x50
[ 40.780010] [<ffffffffa032b715>] acm_tty_open+0x35/0x230 [cdc_acm]
[ 40.780010] [<ffffffff813c1087>] tty_open+0x247/0x5d0
[ 40.780010] [<ffffffff811b5408>] chrdev_open+0x258/0x350
[ 40.780010] [<ffffffff811ad9a4>] __dentry_open+0x384/0x550
[ 40.780010] [<ffffffff811af194>] nameidata_to_filp+0x74/0x80
[ 40.780010] [<ffffffff811c0b6c>] do_last+0x26c/0x920
[ 40.780010] [<ffffffff811c1335>] path_openat+0xd5/0x3e0
[ 40.780010] [<ffffffff811c1762>] do_filp_open+0x42/0xa0
[ 40.780010] [<ffffffff811af297>] do_sys_open+0xf7/0x1d0
[ 40.780010] [<ffffffff811af390>] sys_open+0x20/0x30
[ 40.780010] [<ffffffff81689f82>] system_call_fastpath+0x16/0x1b
[ 40.780010]
[ 40.780010] -> #0 (big_tty_mutex){+.+.+.}:
[ 40.780010] [<ffffffff810c112e>] __lock_acquire+0x16ce/0x1c40
[ 40.780010] [<ffffffff810c1d9d>] lock_acquire+0x9d/0x210
[ 40.780010] [<ffffffff8168003e>] __mutex_lock_common+0x5e/0x4f0
[ 40.780010] [<ffffffff81680604>] mutex_lock_nested+0x44/0x50
[ 40.780010] [<ffffffff81682807>] tty_lock+0x17/0x19
[ 40.780010] [<ffffffff813c91ad>] tty_port_close_start+0x17d/0x210
[ 40.780010] [<ffffffffa032b32f>] acm_tty_close+0x4f/0xc0 [cdc_acm]
[ 40.780010] [<ffffffff813c09e7>] tty_release+0x167/0x5c0
[ 40.780010] [<ffffffff811b252e>] fput+0xfe/0x2d0
[ 40.780010] [<ffffffff811adee9>] filp_close+0x69/0x90
[ 40.780010] [<ffffffff811ae1d0>] sys_close+0xc0/0x1a0
[ 40.780010] [<ffffffff81689f82>] system_call_fastpath+0x16/0x1b
[ 40.780010]
[ 40.780010] other info that might help us debug this:
[ 40.780010]
[ 40.780010] Possible unsafe locking scenario:
[ 40.780010]
[ 40.780010] CPU0 CPU1
[ 40.780010] ---- ----
[ 40.780010] lock(open_mutex);
[ 40.780010] lock(big_tty_mutex);
[ 40.780010] lock(open_mutex);
[ 40.780010] lock(big_tty_mutex);
[ 40.780010]
[ 40.780010] *** DEADLOCK ***
[ 40.780010]
[ 40.780010] 1 lock held by modem-manager/1141:
[ 40.780010] #0: (open_mutex){+.+...}, at: [<ffffffffa032b321>] acm_tty_close+0x41/0xc0 [cdc_acm]
[ 40.780010]
[ 40.780010] stack backtrace:
[ 40.780010] Pid: 1141, comm: modem-manager Not tainted 3.2.0-rc2+ #8
[ 40.780010] Call Trace:
[ 40.780010] [<ffffffff81675378>] print_circular_bug+0x202/0x213
[ 40.780010] [<ffffffff810c112e>] __lock_acquire+0x16ce/0x1c40
[ 40.780010] [<ffffffff81021f62>] ? native_sched_clock+0x22/0x70
[ 40.780010] [<ffffffff810ae2c5>] ? sched_clock_local+0x25/0x90
[ 40.780010] [<ffffffff810c1d9d>] lock_acquire+0x9d/0x210
[ 40.780010] [<ffffffff81682807>] ? tty_lock+0x17/0x19
[ 40.780010] [<ffffffff810c180a>] ? lock_release_non_nested+0x16a/0x350
[ 40.780010] [<ffffffff8168003e>] __mutex_lock_common+0x5e/0x4f0
[ 40.780010] [<ffffffff81682807>] ? tty_lock+0x17/0x19
[ 40.780010] [<ffffffff810c2796>] ? mark_held_locks+0x86/0x150
[ 40.780010] [<ffffffff816807ae>] ? mutex_unlock+0xe/0x10
[ 40.780010] [<ffffffff81682807>] ? tty_lock+0x17/0x19
[ 40.780010] [<ffffffff81680604>] mutex_lock_nested+0x44/0x50
[ 40.780010] [<ffffffff81682807>] tty_lock+0x17/0x19
[ 40.780010] [<ffffffff813c91ad>] tty_port_close_start+0x17d/0x210
[ 40.780010] [<ffffffffa032b32f>] acm_tty_close+0x4f/0xc0 [cdc_acm]
[ 40.780010] [<ffffffff813c09e7>] tty_release+0x167/0x5c0
[ 40.780010] [<ffffffff81021fb9>] ? sched_clock+0x9/0x10
[ 40.780010] [<ffffffff810ae2c5>] ? sched_clock_local+0x25/0x90
[ 40.780010] [<ffffffff811b252e>] fput+0xfe/0x2d0
[ 40.780010] [<ffffffff811adee9>] filp_close+0x69/0x90
[ 40.780010] [<ffffffff811ae1d0>] sys_close+0xc0/0x1a0
[ 40.780010] [<ffffffff81689f82>] system_call_fastpath+0x16/0x1b

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