I got this once while testing an USB audio device. Appeareantly not reproducable.
Daniel
Feb 21 14:26:29 jup kernel: [69661.385427] Feb 21 14:26:29 jup kernel: [69661.385430] ======================================================= Feb 21 14:26:29 jup kernel: [69661.385435] [ INFO: possible circular locking dependency detected ] Feb 21 14:26:29 jup kernel: [69661.385439] 2.6.33-rc8 #21 Feb 21 14:26:29 jup kernel: [69661.385441] ------------------------------------------------------- Feb 21 14:26:29 jup kernel: [69661.385444] aplay/11761 is trying to acquire lock: Feb 21 14:26:29 jup kernel: [69661.385446] (sysfs_mutex){+.+.+.}, at: [<c10f0668>] sysfs_get_dirent+0x15/0x4c Feb 21 14:26:29 jup kernel: [69661.385457] Feb 21 14:26:29 jup kernel: [69661.385457] but task is already holding lock: Feb 21 14:26:29 jup kernel: [69661.385460] (&pcm->open_mutex){+.+.+.}, at: [<fb68bc8e>] snd_pcm_release+0x55/0x9e [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385474] Feb 21 14:26:29 jup kernel: [69661.385474] which lock already depends on the new lock. Feb 21 14:26:29 jup kernel: [69661.385476] Feb 21 14:26:29 jup kernel: [69661.385478] Feb 21 14:26:29 jup kernel: [69661.385479] the existing dependency chain (in reverse order) is: Feb 21 14:26:29 jup kernel: [69661.385481] Feb 21 14:26:29 jup kernel: [69661.385482] -> #2 (&pcm->open_mutex){+.+.+.}: Feb 21 14:26:29 jup kernel: [69661.385487] [<c1059070>] __lock_acquire+0x10ff/0x1422 Feb 21 14:26:29 jup kernel: [69661.385493] [<c105943b>] lock_acquire+0xa8/0xbf Feb 21 14:26:29 jup kernel: [69661.385498] [<c13720d3>] mutex_lock_nested+0x47/0x2b2 Feb 21 14:26:29 jup kernel: [69661.385503] [<fb68bc8e>] snd_pcm_release+0x55/0x9e [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385513] [<c10aabe9>] __fput+0xeb/0x196 Feb 21 14:26:29 jup kernel: [69661.385517] [<c10aacad>] fput+0x19/0x1b Feb 21 14:26:29 jup kernel: [69661.385522] [<c109ae3b>] remove_vma+0x39/0x58 Feb 21 14:26:29 jup kernel: [69661.385528] [<c109bab3>] do_munmap+0x23c/0x259 Feb 21 14:26:29 jup kernel: [69661.385532] [<c109bb00>] sys_munmap+0x30/0x3f Feb 21 14:26:29 jup kernel: [69661.385536] [<c10028d0>] sysenter_do_call+0x12/0x36 Feb 21 14:26:29 jup kernel: [69661.385541] Feb 21 14:26:29 jup kernel: [69661.385542] -> #1 (&mm->mmap_sem){++++++}: Feb 21 14:26:29 jup kernel: [69661.385547] [<c1059070>] __lock_acquire+0x10ff/0x1422 Feb 21 14:26:29 jup kernel: [69661.385551] [<c105943b>] lock_acquire+0xa8/0xbf Feb 21 14:26:29 jup kernel: [69661.385556] [<c10968db>] might_fault+0x6b/0x88 Feb 21 14:26:29 jup kernel: [69661.385561] [<c11b3cf0>] copy_to_user+0x2c/0xfc Feb 21 14:26:29 jup kernel: [69661.385565] [<c10b5e73>] filldir64+0x97/0xcd Feb 21 14:26:29 jup kernel: [69661.385570] [<c10f0534>] sysfs_readdir+0x117/0x14b Feb 21 14:26:29 jup kernel: [69661.385574] [<c10b6085>] vfs_readdir+0x68/0x94 Feb 21 14:26:29 jup kernel: [69661.385578] [<c10b6114>] sys_getdents64+0x63/0xa0 Feb 21 14:26:29 jup kernel: [69661.385582] [<c10028d0>] sysenter_do_call+0x12/0x36 Feb 21 14:26:29 jup kernel: [69661.385587] Feb 21 14:26:29 jup kernel: [69661.385587] -> #0 (sysfs_mutex){+.+.+.}: Feb 21 14:26:29 jup kernel: [69661.385592] [<c1058dc6>] __lock_acquire+0xe55/0x1422 Feb 21 14:26:29 jup kernel: [69661.385597] [<c105943b>] lock_acquire+0xa8/0xbf Feb 21 14:26:29 jup kernel: [69661.385601] [<c13720d3>] mutex_lock_nested+0x47/0x2b2 Feb 21 14:26:29 jup kernel: [69661.385605] [<c10f0668>] sysfs_get_dirent+0x15/0x4c Feb 21 14:26:29 jup kernel: [69661.385609] [<c10f1b4a>] sysfs_remove_group+0x1e/0xa3 Feb 21 14:26:29 jup kernel: [69661.385614] [<c12359b8>] dpm_sysfs_remove+0x10/0x12 Feb 21 14:26:29 jup kernel: [69661.385619] [<c123114c>] device_del+0x33/0x154 Feb 21 14:26:29 jup kernel: [69661.385625] [<c1231278>] device_unregister+0xb/0x15 Feb 21 14:26:29 jup kernel: [69661.385629] [<c129a209>] usb_remove_ep_devs+0x15/0x1f Feb 21 14:26:29 jup kernel: [69661.385635] [<c12943ff>] remove_intf_ep_devs+0x21/0x32 Feb 21 14:26:29 jup kernel: [69661.385640] [<c12954ea>] usb_set_interface+0x18c/0x22c Feb 21 14:26:29 jup kernel: [69661.385644] [<fc703cd7>] snd_usb_playback_close+0x20/0x33 [snd_usb_audio] Feb 21 14:26:29 jup kernel: [69661.385654] [<fb68bc10>] snd_pcm_release_substream+0x3d/0x66 [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385664] [<fb68bc95>] snd_pcm_release+0x5c/0x9e [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385673] [<c10aabe9>] __fput+0xeb/0x196 Feb 21 14:26:29 jup kernel: [69661.385677] [<c10aacad>] fput+0x19/0x1b Feb 21 14:26:29 jup kernel: [69661.385681] [<c109ae3b>] remove_vma+0x39/0x58 Feb 21 14:26:29 jup kernel: [69661.385685] [<c109bab3>] do_munmap+0x23c/0x259 Feb 21 14:26:29 jup kernel: [69661.385689] [<c109bb00>] sys_munmap+0x30/0x3f Feb 21 14:26:29 jup kernel: [69661.385693] [<c10028d0>] sysenter_do_call+0x12/0x36 Feb 21 14:26:29 jup kernel: [69661.385698] Feb 21 14:26:29 jup kernel: [69661.385698] other info that might help us debug this: Feb 21 14:26:29 jup kernel: [69661.385700] Feb 21 14:26:29 jup kernel: [69661.385702] 2 locks held by aplay/11761: Feb 21 14:26:29 jup kernel: [69661.385705] #0: (&mm->mmap_sem){++++++}, at: [<c109baf3>] sys_munmap+0x23/0x3f Feb 21 14:26:29 jup kernel: [69661.385711] #1: (&pcm->open_mutex){+.+.+.}, at: [<fb68bc8e>] snd_pcm_release+0x55/0x9e [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385723] Feb 21 14:26:29 jup kernel: [69661.385724] stack backtrace: Feb 21 14:26:29 jup kernel: [69661.385727] Pid: 11761, comm: aplay Not tainted 2.6.33-rc8 #21 Feb 21 14:26:29 jup kernel: [69661.385730] Call Trace: Feb 21 14:26:29 jup kernel: [69661.385735] [<c137062c>] ? printk+0xf/0x11 Feb 21 14:26:29 jup kernel: [69661.385740] [<c1057b26>] print_circular_bug+0x90/0x9c Feb 21 14:26:29 jup kernel: [69661.385744] [<c1058dc6>] __lock_acquire+0xe55/0x1422 Feb 21 14:26:29 jup kernel: [69661.385748] [<c105917f>] ? __lock_acquire+0x120e/0x1422 Feb 21 14:26:29 jup kernel: [69661.385753] [<c103d4d3>] ? try_to_del_timer_sync+0x9c/0xa4 Feb 21 14:26:29 jup kernel: [69661.385758] [<c105943b>] lock_acquire+0xa8/0xbf Feb 21 14:26:29 jup kernel: [69661.385762] [<c10f0668>] ? sysfs_get_dirent+0x15/0x4c Feb 21 14:26:29 jup kernel: [69661.385766] [<c10f0668>] ? sysfs_get_dirent+0x15/0x4c Feb 21 14:26:29 jup kernel: [69661.385769] [<c13720d3>] mutex_lock_nested+0x47/0x2b2 Feb 21 14:26:29 jup kernel: [69661.385773] [<c10f0668>] ? sysfs_get_dirent+0x15/0x4c Feb 21 14:26:29 jup kernel: [69661.385777] [<c137187f>] ? __mutex_unlock_slowpath+0xe9/0x105 Feb 21 14:26:29 jup kernel: [69661.385781] [<c10572e5>] ? trace_hardirqs_on_caller+0xff/0x120 Feb 21 14:26:29 jup kernel: [69661.385785] [<c10f0668>] sysfs_get_dirent+0x15/0x4c Feb 21 14:26:29 jup kernel: [69661.385789] [<c10f1b4a>] sysfs_remove_group+0x1e/0xa3 Feb 21 14:26:29 jup kernel: [69661.385793] [<c12359b8>] dpm_sysfs_remove+0x10/0x12 Feb 21 14:26:29 jup kernel: [69661.385797] [<c123114c>] device_del+0x33/0x154 Feb 21 14:26:29 jup kernel: [69661.385801] [<c1231278>] device_unregister+0xb/0x15 Feb 21 14:26:29 jup kernel: [69661.385805] [<c129a209>] usb_remove_ep_devs+0x15/0x1f Feb 21 14:26:29 jup kernel: [69661.385809] [<c12943ff>] remove_intf_ep_devs+0x21/0x32 Feb 21 14:26:29 jup kernel: [69661.385813] [<c12954ea>] usb_set_interface+0x18c/0x22c Feb 21 14:26:29 jup kernel: [69661.385822] [<fc703cd7>] snd_usb_playback_close+0x20/0x33 [snd_usb_audio] Feb 21 14:26:29 jup kernel: [69661.385830] [<fb68bc10>] snd_pcm_release_substream+0x3d/0x66 [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385839] [<fb68bc95>] snd_pcm_release+0x5c/0x9e [snd_pcm] Feb 21 14:26:29 jup kernel: [69661.385843] [<c10aabe9>] __fput+0xeb/0x196 Feb 21 14:26:29 jup kernel: [69661.385847] [<c10aacad>] fput+0x19/0x1b Feb 21 14:26:29 jup kernel: [69661.385851] [<c109ae3b>] remove_vma+0x39/0x58 Feb 21 14:26:29 jup kernel: [69661.385854] [<c109bab3>] do_munmap+0x23c/0x259 Feb 21 14:26:29 jup kernel: [69661.385858] [<c109bb00>] sys_munmap+0x30/0x3f Feb 21 14:26:29 jup kernel: [69661.385862] [<c10028d0>] sysenter_do_call+0x12/0x36