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Date: Fri, 28 Mar 2008 10:34:30 -0400 (EDT)
From: Alan Stern <stern@rowland.harvard.edu>
X-X-Sender: stern@iolanthe.rowland.org
To: Mark Lord <lkml@rtr.ca>
cc: Greg KH <gregkh@suse.de>, <jkosina@suse.cz>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       <linux-usb@vger.kernel.org>, Pavel Machek <pavel@suse.cz>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: 2.6.25-rc7:  Ugh.
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On Thu, 27 Mar 2008, Mark Lord wrote:

> Same thing happens when I rmmod usbhid, and then rmmod ehci_hcd.
> The rmmod ehci_hcd hangs.
> 
> But since the rest of the system is still alive, including the non-USB touchpad(!),
> here is the alt-sysrq-t from syslog:
> 
> rmmod         D f74c2ddc     0  4538   4492
>        f6d3b200 00000086 f74c2c90 f74c2ddc c281e840 00000001 c01131be 00000000 
>        00000001 c0324a00 c0324a00 00000000 00000001 7fffffff 7fffffff f653cea8 
>        00000002 c02906f8 00000000 00000012 c038f6aa 00000086 c011aa05 00000000 
> Call Trace:
>  [__wake_up_common+46/88] __wake_up_common+0x2e/0x58
>  [schedule_timeout+19/134] schedule_timeout+0x13/0x86
>  [wake_up_klogd+43/45] wake_up_klogd+0x2b/0x2d
>  [wait_for_common+205/308] wait_for_common+0xcd/0x134
>  [default_wake_function+0/8] default_wake_function+0x0/0x8
>  [__cancel_work_timer+237/312] __cancel_work_timer+0xed/0x138
>  [wq_barrier_func+0/8] wq_barrier_func+0x0/0x8
>  [<f889f684>] usb_remove_hcd+0x63/0xd7 [usbcore]
>  [<f88a858e>] usb_hcd_pci_remove+0x15/0x68 [usbcore]
>  [pci_device_remove+22/53] pci_device_remove+0x16/0x35
>  [__device_release_driver+88/118] __device_release_driver+0x58/0x76
>  [driver_detach+122/182] driver_detach+0x7a/0xb6
>  [bus_remove_driver+96/126] bus_remove_driver+0x60/0x7e
>  [pci_unregister_driver+30/95] pci_unregister_driver+0x1e/0x5f
>  [sys_delete_module+388/445] sys_delete_module+0x184/0x1bd
>  [remove_vma+49/54] remove_vma+0x31/0x36
>  [do_page_fault+506/1232] do_page_fault+0x1fa/0x4d0
>  [sysenter_past_esp+95/133] sysenter_past_esp+0x5f/0x85
>  =======================
> 
> If nothing else, this should point to where USB is getting deadlocked.
> 
> ??

rmmod is hanging up in a call to cancel_work_sync(), which means the
real problem is in the workqueue.  It's quite understandable that you
wouldn't want to go any further into debugging this, but in case you
don't mind, the workqueue task is ksuspend_usbd.

On the other hand, I don't understand how problems with the RTC 
configuration could cause this sort of result.

Alan Stern

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