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Date: Fri, 5 Aug 2011 08:17:47 -0700
From: Greg KH <gregkh@suse.de>
To: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: wfp5p@virginia.edu, linux-kernel@vger.kernel.org
Subject: Re: Staging: serqt_usb2: kmalloc(GFP_NOIO) with spinlock held in
 qt_break() and qt_tiocmset()
Message-ID: <20110805151747.GB18527@suse.de>
References: <4E3BFF9E.9060504@ispras.ru>
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On Fri, Aug 05, 2011 at 06:35:10PM +0400, Alexey Khoroshilov wrote:
> qt_break() calls usb_control_msg() with spinlock held,

Ick, not good, that will sleep.

> while usb_control_msg() calls kmalloc(GFP_NOIO) and indirectly usb_alloc_urb(GFP_NOIO).

You forgot the obvious call to wait_for_completion_timeout() in the
usb_control_msg() callchain that shows that a spinlock is not a good
thing to be using here :)

> The same is true for qt_tiocmget() and qt_tiocmset().
> 
> Is replacing spinlock with mutex an appropriate solution to fix the issue?

Yes, it sounds like it.

patches gladly accepted.

thanks,

greg k-h