linux-kernel - Re: Staging: serqt_usb2: kmalloc(GFP_NOIO) with spinlock held in qt_break() and qt

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Date:	Fri, 5 Aug 2011 08:17:47 -0700
From:	Greg KH <gregkh@...e.de>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>
Cc:	wfp5p@...ginia.edu, linux-kernel@...r.kernel.org
Subject: Re: Staging: serqt_usb2: kmalloc(GFP_NOIO) with spinlock held in
 qt_break() and qt_tiocmset()

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
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