[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Initializing cgroup subsys cpu
[ 0.000000] Linux version 3.8.0-1-linaro-vexpress (buildd@wani10) (gcc version 4.7.2 (Ubuntu/Linaro 4.7.2-2ubuntu1) ) #1ubuntu1~ci+130125174543-Ubuntu SMP Sat Jan 26 00:47:35 UTC 201
...
[ 602.909859]
[ 602.909864] ======================================================
[ 602.909868] [ INFO: possible circular locking dependency detected ]
[ 602.909877] 3.8.0-1-linaro-vexpress #1ubuntu1~ci+130125174543-Ubuntu Not tainted
[ 602.909881] -------------------------------------------------------
[ 602.909887] kworker/0:1/376 is trying to acquire lock:
[ 602.909922] ((fb_notifier_list).rwsem){.+.+.+}, at: [<c00385b9>] __blocking_notifier_call_chain+0x1d/0x40
[ 602.909926]
[ 602.909926] but task is already holding lock:
[ 602.909953] (console_lock){+.+.+.}, at: [<c0285103>] console_callback+0xf/0xe0
[ 602.909957]
[ 602.909957] which lock already depends on the new lock.
[ 602.909957]
[ 602.909960]
[ 602.909960] the existing dependency chain (in reverse order) is:
[ 602.909976]
[ 602.909976] -> #1 (console_lock){+.+.+.}:
[ 602.909994] [<c005b041>] __lock_acquire+0x29d/0x858
[ 602.910010] [<c005b93f>] lock_acquire+0x5f/0xbc
[ 602.910027] [<c001d2f5>] console_lock+0x31/0x40
[ 602.910041] [<c028350f>] register_con_driver+0x27/0xe8
[ 602.910054] [<c0283ded>] take_over_console+0x19/0x240
[ 602.910071] [<c0269263>] fbcon_takeover+0x3b/0x88
[ 602.910083] [<c00383ed>] notifier_call_chain+0x45/0x54
[ 602.910097] [<c00385cb>] __blocking_notifier_call_chain+0x2f/0x40
[ 602.910110] [<c00385f3>] blocking_notifier_call_chain+0x17/0x1c
[ 602.910123] [<c0265d35>] register_framebuffer+0x109/0x1cc
[ 602.910135] [<c026fdbb>] hdlcd_probe+0x507/0x5d0
[ 602.910148] [<c02909d3>] platform_drv_probe+0x17/0x18
[ 602.910159] [<c028fd49>] driver_probe_device+0x51/0x170
[ 602.910169] [<c028febf>] __driver_attach+0x57/0x58
[ 602.910185] [<c028ec9b>] bus_for_each_dev+0x2b/0x4c
[ 602.910195] [<c028f7dd>] bus_add_driver+0xe5/0x170
[ 602.910206] [<c02901ef>] driver_register+0x43/0xd0
[ 602.910218] [<c0008511>] do_one_initcall+0xc9/0x114
[ 602.910231] [<c03d5ceb>] kernel_init+0xcf/0x1ec
[ 602.910245] [<c000ce95>] ret_from_fork+0x11/0x20
[ 602.910261]
[ 602.910261] -> #0 ((fb_notifier_list).rwsem){.+.+.+}:
[ 602.910274] [<c005a799>] validate_chain.isra.26+0xafd/0xbe4
[ 602.910288] [<c005b041>] __lock_acquire+0x29d/0x858
[ 602.910301] [<c005b93f>] lock_acquire+0x5f/0xbc
[ 602.910316] [<c03dfe8d>] down_read+0x25/0x30
[ 602.910329] [<c00385b9>] __blocking_notifier_call_chain+0x1d/0x40
[ 602.910342] [<c00385f3>] blocking_notifier_call_chain+0x17/0x1c
[ 602.910354] [<c0264e7d>] fb_blank+0x29/0x64
[ 602.910364] [<c026a859>] fbcon_blank+0x135/0x1ac
[ 602.910377] [<c0283471>] do_blank_screen+0x109/0x180
[ 602.910391] [<c028513d>] console_callback+0x49/0xe0
[ 602.910402] [<c00304a1>] process_one_work+0x12d/0x3c4
[ 602.910413] [<c00309a7>] worker_thread+0x117/0x344
[ 602.910426] [<c0033dd3>] kthread+0x77/0x84
[ 602.910439] [<c000ce95>] ret_from_fork+0x11/0x20
[ 602.910443]
[ 602.910443] other info that might help us debug this:
[ 602.910443]
[ 602.910446] Possible unsafe locking scenario:
[ 602.910446]
[ 602.910450] CPU0 CPU1
[ 602.910453] ---- ----
[ 602.910463] lock(console_lock);
[ 602.910472] lock((fb_notifier_list).rwsem);
[ 602.910481] lock(console_lock);
[ 602.910489] lock((fb_notifier_list).rwsem);
[ 602.910493]
[ 602.910493] *** DEADLOCK ***
[ 602.910493]
[ 602.910499] 3 locks held by kworker/0:1/376:
[ 602.910523] #0: (events){.+.+.+}, at: [<c003044e>] process_one_work+0xda/0x3c4
[ 602.910546] #1: (console_work){+.+...}, at: [<c003044e>] process_one_work+0xda/0x3c4
[ 602.910572] #2: (console_lock){+.+.+.}, at: [<c0285103>] console_callback+0xf/0xe0
[ 602.910575]
[ 602.910575] stack backtrace:
[ 602.910596] [<c0011fd1>] (unwind_backtrace+0x1/0x9c) from [<c03da9cb>] (print_circular_bug+0x1a7/0x1f0)
[ 602.910614] [<c03da9cb>] (print_circular_bug+0x1a7/0x1f0) from [<c005a799>] (validate_chain.isra.26+0xafd/0xbe4)
[ 602.910632] [<c005a799>] (validate_chain.isra.26+0xafd/0xbe4) from [<c005b041>] (__lock_acquire+0x29d/0x858)
[ 602.910649] [<c005b041>] (__lock_acquire+0x29d/0x858) from [<c005b93f>] (lock_acquire+0x5f/0xbc)
[ 602.910665] [<c005b93f>] (lock_acquire+0x5f/0xbc) from [<c03dfe8d>] (down_read+0x25/0x30)
[ 602.910683] [<c03dfe8d>] (down_read+0x25/0x30) from [<c00385b9>] (__blocking_notifier_call_chain+0x1d/0x40)
[ 602.910701] [<c00385b9>] (__blocking_notifier_call_chain+0x1d/0x40) from [<c00385f3>] (blocking_notifier_call_chain+0x17/0x1c)
[ 602.910718] [<c00385f3>] (blocking_notifier_call_chain+0x17/0x1c) from [<c0264e7d>] (fb_blank+0x29/0x64)
[ 602.910732] [<c0264e7d>] (fb_blank+0x29/0x64) from [<c026a859>] (fbcon_blank+0x135/0x1ac)
[ 602.910746] [<c026a859>] (fbcon_blank+0x135/0x1ac) from [<c0283471>] (do_blank_screen+0x109/0x180)
[ 602.910764] [<c0283471>] (do_blank_screen+0x109/0x180) from [<c028513d>] (console_callback+0x49/0xe0)
[ 602.910780] [<c028513d>] (console_callback+0x49/0xe0) from [<c00304a1>] (process_one_work+0x12d/0x3c4)
[ 602.910793] [<c00304a1>] (process_one_work+0x12d/0x3c4) from [<c00309a7>] (worker_thread+0x117/0x344)
[ 602.910808] [<c00309a7>] (worker_thread+0x117/0x344) from [<c0033dd3>] (kthread+0x77/0x84)
[ 602.910825] [<c0033dd3>] (kthread+0x77/0x84) from [<c000ce95>] (ret_from_fork+0x11/0x20)