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List:       linux-usb
Subject:    Re: [PATCH] cdc-acm.c: fix recursive lock in acm_start_wb error path
From:       Oliver Neukum <oliver () neukum ! org>
Date:       2008-10-31 11:49:54
Message-ID: 200810311249.55313.oliver () neukum ! org
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Am Freitag, 31. Oktober 2008 12:16:18 schrieb Brandon Philips:
> This patch fixes an obvious bug in cdc-acm by avoiding a recursive lock on
> acm_start_wb()'s error path.
> 
> But after applying the fix I started hitting an infinite loop in uhci that
> prints this with usb debug on:
> 
>   usb 4-1: uhci_result_common: failed with status 440000
>   ...
>   usb 4-1: uhci_result_common: failed with status 440000
> 
> I can reproduce this UHCI bug by unplugging and replugging the device a
> few times while a program opens the device and starts writing data to
> it. Here are outputs from sysrq and modprobe uhci_hcd debug=3:
> 
> ("python" is the test process)
> http://ifup.org/~philips/cdc-acm-440000-trace.txt 
> http://ifup.org/~philips/cdc-acm-sysrq.txt
> http://ifup.org/~philips/cdc-acm-uhci-hcd-debug-3.txt
> 
> Any ideas?

It looks like the write path does not detect that the device is gone
and never stops submitting. Can you kill the programm that writes?

	Regards
		Oliver

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