Subject: Re: [PATCH 4/4] usb: libusual: locking cleanup
From: Daniel Walker <dwalker@mvista.com>
To: Pete Zaitcev <zaitcev@redhat.com>
Cc: akpm@linux-foundation.org, mingo@elte.hu, linux-kernel@vger.kernel.org,
       linux@bohmer.net, jonathan@jonmasters.org, matthias.kaehlcke@gmail.com,
       kjwinchester@gmail.com
In-Reply-To: <20071222233733.3a4e94b0.zaitcev@redhat.com>
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	 <20071222233733.3a4e94b0.zaitcev@redhat.com>
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Date: Sun, 23 Dec 2007 08:46:37 -0800
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On Sat, 2007-12-22 at 23:37 -0800, Pete Zaitcev wrote:
> On Sat, 22 Dec 2007 09:01:50 -0800, Daniel Walker <dwalker@mvista.com> wrote:
> 
> > Then in usu_probe_thread() your basically stopping it at the start of
> > the function with a down(), and the up() is just ancillary .. So you
> > could easily move the up() further down in the function and still have
> > the same level of exclusion.. 
> 
> The unfortunate complication here is request_module. I didn't want to
> keep a semaphore locked across it, in case child waits for something.
> I wonder if there may be some deadlock that we cannot foresee.
> But I guess it won't hurt to try.

I noticed you also have a spinlock held in usu_probe_thread(), the
usu_lock.. That spinlock would preclude anything inside request_module()
from sleeping..

One thing that has bothered me is that I don't see a reason why this
couldn't become a complete, yet you have a comment which says that it
can't be a complete.. I honestly didn't understand the comment.. I would
imagine that you tried a complete , and it didn't work?

> I tested the patch and it seems to work ok.

Great, thanks ..

Daniel

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