linux-kernel - Re: [PATCH] staging: usbip: stub_dev: Fixed oops during removal of usbip

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Message-ID: <20120918093619.GO13767@mwanda>
Date:	Tue, 18 Sep 2012 12:36:19 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	navin patidar <navinp@...c.in>
Cc:	gregkh@...uxfoundation.org, mfm@...eddisk.com,
	devel@...verdev.osuosl.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: usbip: stub_dev: Fixed oops during removal of
 usbip_host

On Tue, Sep 18, 2012 at 03:02:15PM +0530, navin patidar wrote:
> On Tue, Sep 18, 2012 at 1:10 PM, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > On Tue, Sep 18, 2012 at 09:30:06AM +0530, navin patidar wrote:
> >> stub_device_reset should set kernel thread pointers to NULL.
> >> so that at the time of usbip_host removal stub_shoutdown_connection
> >> doesn't try to kill kernel threads which are already killed.
> >>
> >
> > If you have the Oops output, that's always nice to put in the commit
> > message.
> 
> i'll surely keep this in mind  before submitting further patches.
> 
> > Why don't you set the pointers to NULL in stub_shutdown_connection()
> > since that's where you actually kill the threads.  Setting them to
> > NULL in stub_device_reset() will (sometimes) solve the problem but
> > it gives you a new problem of a resource leak.
> 
>  stub_device_reset() always gets executed after
> stub_shutdown_connection() , never before.
> 

No it isn't.  Read event_handler() more carefully.  They can be
executed independently.

In other words, stub_shutdown_connection() can be called without
calling stub_device_reset() and stub_device_reset() can be called
without stub_shutdown_connection().  If either of those happen then
it causes a problem with the patch you have just sent.

regards,
dan carpenter

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