linux-kernel - [PATCH] usb-serial regression fix

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Message-ID: <20070312225922.GA4064@blackbean.org>
Date:	Mon, 12 Mar 2007 15:59:22 -0700
From:	Jim Radford <radford@...ckbean.org>
To:	Greg KH <greg@...ah.com>
Cc:	Mark Lord <lkml@....ca>, linux-usb-devel@...ts.sourceforge.net,
	Oliver Neukum <oneukum@...e.de>, Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] usb-serial regression fix

On Mon, Mar 12, 2007 at 03:42:35PM -0700, Jim Radford wrote:
> On Mon, Mar 12, 2007 at 01:33:31PM -0700, Greg KH wrote:
> > On Mon, Mar 12, 2007 at 04:22:22PM -0400, Mark Lord wrote:
> > > Oliver Neukum wrote:
> > > >>Mark Lord wrote:
> > > >>>Okay, from that part (above), the problem is obvious:
> > > >>>in that the "MCT U232 converter now disconnected" appears,
> > > >>>and then we continue to try and call the driver's method.. Oops!
> 
> > > >IMHO shutdown() is using serial->port[] and bombs.
> > > >Could you reverse the order here?
> 
> > > Yup.  Fixed.  Tested.  Works.
> 
> > > This patch fixes the Oops that otherwise occurs whenever
> > > a USB serial adapter is unplugged from a system, as well
> > > the Oops seen when one is in use before resume (to RAM).
> 
> > Argh, no, this change was done to help the ftdi drivers out.
> 
> > Look at changeset d9a7ecacac5f8274d2afce09aadcf37bdb42b93a in Linus's
> > tree from Jim Radford:
> > 	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d9a7ecacac5f8274d2afce09aadcf37bdb42b93a
> > 
> > It makes this change because the usb-serial drivers need the port
> > devices when the port_remove() callbacks happen.  Otherwise you get an
> > oops that way.
> 
> > Jim, can you take a look at this and see if you can figure something
> > out?
> 
> The problem is really the
> 
>    serial->port[i] = NULL;
> 
> line after device_unregister() which is used to flag "fake" devices
> that don't need legacy cleanup later in the destrol_serial.  That
> flagging should be done using a *real* flag, and not by overloading
> the ->port[i] pointer since we require it to be non-NULL in
> ->shutdown() in all drivers that are not converted to new
> ->port_probe()/->port_remove() framework (currently all except ftdi).

> I'll work on a patch to do that, but for now, I think you should apply
> Mark's patch to revert the order change since the FTDI driver no
> longer requires the correct ordering of device_unregister() and
> ->shutdown().

Do not NULL serial->port[i] since it is used in ->shutdown().  This
wasn't an issue until the order or ->shutdown() and device_unregister
was corrected.

Signed-Off: Jim Radford <radford@...ckbean.org>

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 8511352..871c9a8 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -145,7 +145,6 @@ static void destroy_serial(struct kref *kref)
        for (i = 0; i < serial->num_ports; ++i)
                if (serial->port[i]->dev.parent != NULL) {
                        device_unregister(&serial->port[i]->dev);
-                       serial->port[i] = NULL;
                }

        if (serial->type->shutdown)

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