[USB] Fix connect/disconnect race

[USB] Fix connect/disconnect race

[Herbert Xu]

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Hi Greg:

This patch was integrated by you in 2.4 six months ago.  Unfortunately
it never got into 2.5.  Without it you can end up with crashes such
as http://bugs.debian.org/218670

Cheers,
-- 
Debian GNU/Linux 3.0 is out! ( http://www.debian.org/ )
Email:  Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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Index: kernel-source-2.5/drivers/usb/core/hub.c
===================================================================
RCS file: /home/gondolin/herbert/src/CVS/debian/kernel-source-2.5/drivers/usb/core/hub.c,v
retrieving revision 1.1.1.15
diff -u -r1.1.1.15 hub.c
--- kernel-source-2.5/drivers/usb/core/hub.c	28 Sep 2003 04:44:16 -0000	1.1.1.15
+++ kernel-source-2.5/drivers/usb/core/hub.c	30 Nov 2003 07:44:40 -0000
@@ -926,7 +926,6 @@
 			break;
 		}
 
-		hub->children[port] = dev;
 		dev->state = USB_STATE_POWERED;
 
 		/* Reset the device, and detect its speed */
@@ -979,8 +978,10 @@
 		dev->dev.parent = dev->parent->dev.parent->parent;
 
 		/* Run it through the hoops (find a driver, etc) */
-		if (!usb_new_device(dev, &hub->dev))
+		if (!usb_new_device(dev, &hub->dev)) {
+			hub->children[port] = dev;
 			goto done;
+		}
 
 		/* Free the configuration if there was an error */
 		usb_put_dev(dev);
@@ -989,7 +990,6 @@
 		delay = HUB_LONG_RESET_TIME;
 	}
 
-	hub->children[port] = NULL;
 	hub_port_disable(hub, port);
 done:
 	up(&usb_address0_sem);

Re: [USB] Fix connect/disconnect race

[Greg KH]

On Sun, Nov 30, 2003 at 06:48:14PM +1100, Herbert Xu wrote:
> Hi Greg:
> 
> This patch was integrated by you in 2.4 six months ago.  Unfortunately
> it never got into 2.5.  Without it you can end up with crashes such
> as http://bugs.debian.org/218670

Thanks, I've applied this and will send it on.

greg k-h

Re: [USB] Fix connect/disconnect race

[Herbert Xu]

On Sun, Nov 30, 2003 at 09:03:34PM -0500, Pete Zaitcev wrote:
> > This patch was integrated by you in 2.4 six months ago.  Unfortunately
> > it never got into 2.5.  Without it you can end up with crashes such
> > as http://bugs.debian.org/218670
> 
> > --- kernel-source-2.5/drivers/usb/core/hub.c	28 Sep 2003 04:44:16 -0000	1.1.1.15
> > +++ kernel-source-2.5/drivers/usb/core/hub.c	30 Nov 2003 07:44:40 -0000
> >  			break;
> >  		}
> >  
> > -		hub->children[port] = dev;
> >  		dev->state = USB_STATE_POWERED;
> >[...]
> >  		/* Run it through the hoops (find a driver, etc) */
> > -		if (!usb_new_device(dev, &hub->dev))
> > +		if (!usb_new_device(dev, &hub->dev)) {
> > +			hub->children[port] = dev;
> >  			goto done;
> > +		}
> 
> I'm surprised you need it. The updated usbfs is supposed
> to be immune. This is probably the reason it wasn't ported.

Well the race occurs between usb_disconnect() initiated by rmmod
uhci-hcd and this function.
-- 
Debian GNU/Linux 3.0 is out! ( http://www.debian.org/ )
Email:  Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [USB] Fix connect/disconnect race

[Pete Zaitcev]

> This patch was integrated by you in 2.4 six months ago.  Unfortunately
> it never got into 2.5.  Without it you can end up with crashes such
> as http://bugs.debian.org/218670

> --- kernel-source-2.5/drivers/usb/core/hub.c	28 Sep 2003 04:44:16 -0000	1.1.1.15
> +++ kernel-source-2.5/drivers/usb/core/hub.c	30 Nov 2003 07:44:40 -0000
>  			break;
>  		}
>  
> -		hub->children[port] = dev;
>  		dev->state = USB_STATE_POWERED;
>[...]
>  		/* Run it through the hoops (find a driver, etc) */
> -		if (!usb_new_device(dev, &hub->dev))
> +		if (!usb_new_device(dev, &hub->dev)) {
> +			hub->children[port] = dev;
>  			goto done;
> +		}

I'm surprised you need it. The updated usbfs is supposed
to be immune. This is probably the reason it wasn't ported.

-- Pete