While toggling rfkill during some tests the following appeared in dmesg:
[ 1865.161780] =======================================================
[ 1865.161790] [ INFO: possible circular locking dependency detected ]
[ 1865.161798] 2.6.33-rc4 #17
[ 1865.161803] -------------------------------------------------------
[ 1865.161809] bash/4773 is trying to acquire lock:
[ 1865.161816] (rfkill_global_mutex){+.+.+.}, at: [<b04fe531>] rfkill_state_store+0x61/0x90
[ 1865.161836]
[ 1865.161838] but task is already holding lock:
[ 1865.161843] (s_active){++++.+}, at: [<b02081dd>] sysfs_get_active_two+0x1d/0x60
[ 1865.161862]
[ 1865.161864] which lock already depends on the new lock.
[ 1865.161867]
[ 1865.161871]
[ 1865.161873] the existing dependency chain (in reverse order) is:
[ 1865.161879]
[ 1865.161881] -> #2 (s_active){++++.+}:
[ 1865.161892] [<b0162812>] __lock_acquire+0xd62/0x1290
[ 1865.161905] [<b0162e02>] lock_acquire+0xc2/0xe0
[ 1865.161914] [<b0208588>] sysfs_addrm_finish+0xb8/0x120
[ 1865.161924] [<b020680a>] sysfs_hash_and_remove+0x4a/0x70
[ 1865.161934] [<b020979c>] sysfs_remove_group+0x4c/0xd0
[ 1865.161944] [<b039a795>] dpm_sysfs_remove+0x15/0x20
[ 1865.161956] [<b039439e>] device_del+0x3e/0x1a0
[ 1865.161968] [<b047c433>] netdev_unregister_kobject+0x23/0x30
[ 1865.161980] [<b046df2b>] rollback_registered_many+0x23b/0x340
[ 1865.161992] [<b046e045>] unregister_netdevice_many+0x15/0x50
[ 1865.162002] [<b04e9f3f>] ieee80211_remove_interfaces+0x7f/0xb0
[ 1865.162014] [<b04dda80>] ieee80211_unregister_hw+0x40/0xe0
[ 1865.162024] [<b0509bb6>] ath5k_pci_remove+0x26/0xd0
[ 1865.162036] [<b02e157e>] pci_device_remove+0x1e/0x40
[ 1865.162048] [<b0396ec8>] __device_release_driver+0x58/0xa0
[ 1865.162058] [<b0396fd5>] device_release_driver+0x25/0x40
[ 1865.162067] [<b0396451>] bus_remove_device+0x81/0xb0
[ 1865.162077] [<b0394474>] device_del+0x114/0x1a0
[ 1865.162086] [<b0394510>] device_unregister+0x10/0x20
[ 1865.162096] [<b02dc286>] pci_stop_bus_device+0x76/0x80
[ 1865.162106] [<b02dc302>] pci_remove_bus_device+0x12/0xb0
[ 1865.162116] [<b042bc78>] eeepc_rfkill_hotplug+0x78/0xf0
[ 1865.162127] [<b042bd07>] eeepc_rfkill_notify+0x17/0x20
[ 1865.162136] [<b030a791>] acpi_ev_notify_dispatch+0x51/0x5c
[ 1865.162149] [<b02fd3f6>] acpi_os_execute_deferred+0x22/0x2d
[ 1865.162160] [<b014935d>] worker_thread+0x1bd/0x2d0
[ 1865.162170] [<b014cdb4>] kthread+0x74/0x80
[ 1865.162180] [<b01032ba>] kernel_thread_helper+0x6/0x10
[ 1865.162191]
[ 1865.162193] -> #1 (rtnl_mutex){+.+.+.}:
[ 1865.162203] [<b0162812>] __lock_acquire+0xd62/0x1290
[ 1865.162213] [<b0162e02>] lock_acquire+0xc2/0xe0
[ 1865.162222] [<b050b087>] mutex_lock_nested+0x57/0x2b0
[ 1865.162233] [<b0478e64>] rtnl_lock+0x14/0x20
[ 1865.162242] [<b04c6415>] cfg80211_rfkill_set_block+0x25/0x80
[ 1865.162252] [<b04fe115>] rfkill_set_block+0x65/0xd0
[ 1865.162261] [<b04fe307>] __rfkill_switch_all+0x67/0x80
[ 1865.162270] [<b04fe3ea>] rfkill_switch_all+0x6a/0x70
[ 1865.162279] [<b04febf1>] rfkill_op_handler+0xd1/0x1a0
[ 1865.162288] [<b014935d>] worker_thread+0x1bd/0x2d0
[ 1865.162297] [<b014cdb4>] kthread+0x74/0x80
[ 1865.162306] [<b01032ba>] kernel_thread_helper+0x6/0x10
[ 1865.162316]
[ 1865.162317] -> #0 (rfkill_global_mutex){+.+.+.}:
[ 1865.162328] [<b0162b4e>] __lock_acquire+0x109e/0x1290
[ 1865.162338] [<b0162e02>] lock_acquire+0xc2/0xe0
[ 1865.162347] [<b050b087>] mutex_lock_nested+0x57/0x2b0
[ 1865.162357] [<b04fe531>] rfkill_state_store+0x61/0x90
[ 1865.162367] [<b039345a>] dev_attr_store+0x2a/0x40
[ 1865.162377] [<b02070e1>] sysfs_write_file+0xa1/0x100
[ 1865.162387] [<b01c10c0>] vfs_write+0xa0/0x130
[ 1865.162398] [<b01c1222>] sys_write+0x42/0x70
[ 1865.162407] [<b0102d90>] sysenter_do_call+0x12/0x36
[ 1865.162416]
[ 1865.162418] other info that might help us debug this:
[ 1865.162421]
[ 1865.162427] 3 locks held by bash/4773:
[ 1865.162431] #0: (&buffer->mutex){+.+.+.}, at: [<b020706a>] sysfs_write_file+0x2a/0x100
[ 1865.162448] #1: (s_active){++++.+}, at: [<b02081f5>] sysfs_get_active_two+0x35/0x60
[ 1865.162465] #2: (s_active){++++.+}, at: [<b02081dd>] sysfs_get_active_two+0x1d/0x60
[ 1865.162481]
[ 1865.162483] stack backtrace:
[ 1865.162490] Pid: 4773, comm: bash Not tainted 2.6.33-rc4 #17
[ 1865.162497] Call Trace:
[ 1865.162506] [<b0509e6d>] ? printk+0x1d/0x1f
[ 1865.162516] [<b01607c9>] print_circular_bug+0xd9/0xe0
[ 1865.162526] [<b0162b4e>] __lock_acquire+0x109e/0x1290
[ 1865.162536] [<b0162e02>] lock_acquire+0xc2/0xe0
[ 1865.162545] [<b04fe531>] ? rfkill_state_store+0x61/0x90
[ 1865.162555] [<b050b087>] mutex_lock_nested+0x57/0x2b0
[ 1865.162563] [<b04fe531>] ? rfkill_state_store+0x61/0x90
[ 1865.162575] [<b02c230c>] ? strict_strtoul+0x4c/0x80
[ 1865.162583] [<b04fe531>] rfkill_state_store+0x61/0x90
[ 1865.162592] [<b04fe4d0>] ? rfkill_state_store+0x0/0x90
[ 1865.162601] [<b039345a>] dev_attr_store+0x2a/0x40
[ 1865.162611] [<b02070e1>] sysfs_write_file+0xa1/0x100
[ 1865.162620] [<b01c10c0>] vfs_write+0xa0/0x130
[ 1865.162629] [<b01c2498>] ? fput+0x8/0x30
[ 1865.162638] [<b0207040>] ? sysfs_write_file+0x0/0x100
[ 1865.162647] [<b01c1222>] sys_write+0x42/0x70
[ 1865.162655] [<b0102d90>] sysenter_do_call+0x12/0x36
--
Sitsofe | http://sucs.org/~sits/