Hi,
I got this today when boot gta04 machine (dts is mostly same as for
beagle-xm) on today's linux-next (with 3.11-rc4 it's not happening):
[ 4.404602] ======================================================
[ 4.411102] [ INFO: possible circular locking dependency detected ]
[ 4.417694] 3.11.0-rc4-next-20130807-dirty #2 Not tainted
[ 4.423339] -------------------------------------------------------
[ 4.429931] getty/767 is trying to acquire lock:
[ 4.434783] (&tty->termios_rwsem){++++..}, at: [<c0308f24>]
n_tty_read+0x3ec/0x958
[ 4.442871]
[ 4.442871] but task is already holding lock:
[ 4.449005] (&ldata->atomic_read_lock){+.+...}, at: [<c0309100>]
n_tty_read+0x5c8/0x958
[ 4.457519]
[ 4.457519] which lock already depends on the new lock.
[ 4.457519]
[ 4.466094]
[ 4.466094] the existing dependency chain (in reverse order) is:
[ 4.473968]
-> #1 (&ldata->atomic_read_lock){+.+...}:
[ 4.479461] [<c0099800>] lock_acquire+0xa0/0xfc
[ 4.484893] [<c0508a34>] mutex_lock_interruptible_nested+0x4c/0x420
[ 4.492126] [<c0309100>] n_tty_read+0x5c8/0x958
[ 4.497528] [<c030367c>] tty_read+0x78/0xc8
[ 4.502563] [<c0112ba8>] vfs_read+0x98/0x140
[ 4.507690] [<c01132a0>] SyS_read+0x3c/0x78
[ 4.512725] [<c0013b00>] ret_fast_syscall+0x0/0x48
[ 4.518432]
-> #0 (&tty->termios_rwsem){++++..}:
[ 4.523468] [<c0098e50>] __lock_acquire+0x195c/0x1b08
[ 4.529418] [<c0099800>] lock_acquire+0xa0/0xfc
[ 4.534820] [<c050a178>] down_read+0x30/0x40
[ 4.539947] [<c0308f24>] n_tty_read+0x3ec/0x958
[ 4.545349] [<c030367c>] tty_read+0x78/0xc8
[ 4.550384] [<c0112ba8>] vfs_read+0x98/0x140
[ 4.555511] [<c01132a0>] SyS_read+0x3c/0x78
[ 4.560546] [<c0013b00>] ret_fast_syscall+0x0/0x48
[ 4.566253]
[ 4.566253] other info that might help us debug this:
[ 4.566253]
[ 4.574645] Possible unsafe locking scenario:
[ 4.574645]
[ 4.580871] CPU0 CPU1
[ 4.585601] ---- ----
[ 4.590362] lock(&ldata->atomic_read_lock);
[ 4.594940] lock(&tty->termios_rwsem);
[ 4.601715] lock(&ldata->atomic_read_lock);
[ 4.608947] lock(&tty->termios_rwsem);
[ 4.613067]
[ 4.613067] *** DEADLOCK ***
[ 4.613067]
[ 4.619293] 2 locks held by getty/767:
[ 4.623229] #0: (&tty->ldisc_sem){.+.+.+}, at: [<c030ac84>]
tty_ldisc_ref_wait+0x14/0x3c
[ 4.631958] #1: (&ldata->atomic_read_lock){+.+...}, at:
[<c0309100>] n_tty_read+0x5c8/0x958
[ 4.640930]
[ 4.640930] stack backtrace:
[ 4.645507] CPU: 0 PID: 767 Comm: getty Not tainted
3.11.0-rc4-next-20130807-dirty #2
[ 4.653778] [<c001b8a4>] (unwind_backtrace+0x0/0xec) from
[<c0017af8>] (show_stack+0x10/0x14)
[ 4.662719] [<c0017af8>] (show_stack+0x10/0x14) from [<c0506c88>]
(dump_stack+0x7c/0x94)
[ 4.671234] [<c0506c88>] (dump_stack+0x7c/0x94) from [<c0504abc>]
(print_circular_bug+0x27c/0x2d0)
[ 4.680633] [<c0504abc>] (print_circular_bug+0x27c/0x2d0) from
[<c0098e50>] (__lock_acquire+0x195c/0x1b08)
[ 4.690795] [<c0098e50>] (__lock_acquire+0x195c/0x1b08) from
[<c0099800>] (lock_acquire+0xa0/0xfc)
[ 4.700195] [<c0099800>] (lock_acquire+0xa0/0xfc) from [<c050a178>]
(down_read+0x30/0x40)
[ 4.708801] [<c050a178>] (down_read+0x30/0x40) from [<c0308f24>]
(n_tty_read+0x3ec/0x958)
[ 4.717407] [<c0308f24>] (n_tty_read+0x3ec/0x958) from [<c030367c>]
(tty_read+0x78/0xc8)
[ 4.725891] [<c030367c>] (tty_read+0x78/0xc8) from [<c0112ba8>]
(vfs_read+0x98/0x140)
[ 4.734130] [<c0112ba8>] (vfs_read+0x98/0x140) from [<c01132a0>]
(SyS_read+0x3c/0x78)
[ 4.742370] [<c01132a0>] (SyS_read+0x3c/0x78) from [<c0013b00>]
(ret_fast_syscall+0x0/0x48)
marek
--
as simple and primitive as possible
-------------------------------------------------
Marek Belisko - OPEN-NANDRA
Freelance Developer
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skype: marekwhite
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