Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> Eric:
>
> This looks like it's up your alley.
I took a quick look at the code and this actually looks like a
legitimate warning.
I may be wrong but it looks like the write method
set_bConfigurationValue disable it's current usb device and attempts
to remove the bConfigurationValue sysfs file, and in doing so waits
for the write to complete. aka deadlock.
This might also be one of the false positives I reworked the code in
2.6.34 to fix, by putting different attributes in different sysfs
classes but it doesn't look like it.
Dave did you also any kind of kernel lockup?
> Alan Stern
>
>
> ---------- Forwarded message ----------
> Date: Thu, 22 Apr 2010 14:55:33 -0400
> From: Dave Jones <davej@xxxxxxxxxx>
> To: linux-usb@xxxxxxxxxxxxxxx
> Subject: lockdep warning (2.6.33.2)
>
> I plugged in my iphone, and got the spew below..
>
> Dave
>
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 2.6.33.2-57.fc13.x86_64 #1
> ---------------------------------------------
> udevd/1228 is trying to acquire lock:
> (s_active){++++.+}, at: [<ffffffff811785ba>] sysfs_addrm_finish+0x36/0x55
>
> but task is already holding lock:
> (s_active){++++.+}, at: [<ffffffff81178776>] sysfs_get_active_two+0x24/0x48
>
> other info that might help us debug this:
> 4 locks held by udevd/1228:
> #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff81177163>] sysfs_write_file+0x3c/0x144
> #1: (s_active){++++.+}, at: [<ffffffff81178776>] sysfs_get_active_two+0x24/0x48
> #2: (s_active){++++.+}, at: [<ffffffff81178783>] sysfs_get_active_two+0x31/0x48
> #3: (&hcd->bandwidth_mutex){+.+...}, at: [<ffffffff8134cd35>] usb_set_configuration+0x260/0x685
>
> stack backtrace:
> Pid: 1228, comm: udevd Not tainted 2.6.33.2-57.fc13.x86_64 #1
> Call Trace:
> [<ffffffff8107f94f>] __lock_acquire+0xcb5/0xd2c
> [<ffffffff8107df48>] ? mark_held_locks+0x52/0x70
> [<ffffffff8107e329>] ? debug_check_no_locks_freed+0x12e/0x145
> [<ffffffff8107e1c8>] ? trace_hardirqs_on_caller+0x111/0x135
> [<ffffffff8107faa2>] lock_acquire+0xdc/0x102
> [<ffffffff811785ba>] ? sysfs_addrm_finish+0x36/0x55
> [<ffffffff8107d300>] ? lockdep_init_map+0x9e/0x113
> [<ffffffff81177d8a>] sysfs_deactivate+0x9a/0x103
> [<ffffffff811785ba>] ? sysfs_addrm_finish+0x36/0x55
> [<ffffffff8107220a>] ? sched_clock_cpu+0xc3/0xce
> [<ffffffff81478d6c>] ? __mutex_unlock_slowpath+0x120/0x132
> [<ffffffff811785ba>] sysfs_addrm_finish+0x36/0x55
> [<ffffffff81176818>] sysfs_hash_and_remove+0x53/0x6a
> [<ffffffff811799b1>] sysfs_remove_group+0x91/0xca
> [<ffffffff812f2b45>] dpm_sysfs_remove+0x19/0x1b
> [<ffffffff812ebbdd>] device_del+0x4c/0x1ab
> [<ffffffff812ebd70>] device_unregister+0x34/0x5b
> [<ffffffff8135207f>] usb_remove_ep_devs+0x23/0x2f
> [<ffffffff8134adb9>] remove_intf_ep_devs+0x37/0x4d
> [<ffffffff8134b00b>] usb_disable_device+0xc4/0x1d8
> [<ffffffff8134cd62>] usb_set_configuration+0x28d/0x685
> [<ffffffff8107df48>] ? mark_held_locks+0x52/0x70
> [<ffffffff8147ace1>] ? _raw_spin_unlock_irqrestore+0x47/0x56
> [<ffffffff813519ef>] set_bConfigurationValue+0x5e/0x88
> [<ffffffff812eaafa>] dev_attr_store+0x20/0x22
> [<ffffffff8117722f>] sysfs_write_file+0x108/0x144
> [<ffffffff81120199>] vfs_write+0xae/0x10b
> [<ffffffff8107e1c8>] ? trace_hardirqs_on_caller+0x111/0x135
> [<ffffffff811202b6>] sys_write+0x4a/0x6e
> [<ffffffff81009c72>] system_call_fastpath+0x16/0x1b
>
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