linux-kernel - Re: [RFC PATCHv2] usb: USB Type-C Connector Class

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Date:	Thu, 19 May 2016 08:43:27 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Oliver Neukum <oneukum@...e.com>
Cc:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Rajaram R <rajaram.officemail@...il.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCHv2] usb: USB Type-C Connector Class

On Thu, May 19, 2016 at 04:48:46PM +0200, Oliver Neukum wrote:
> On Thu, 2016-05-19 at 15:44 +0300, Heikki Krogerus wrote:
> 
> > +	dev->class = &typec_class;
> > +	dev->parent = parent;
> > +	dev->type = &typec_partner_dev_type;
> > +	dev_set_name(dev, "%s-partner", dev_name(&port->dev));
> > +
> > +	ret = device_register(dev);
> > +	if (ret) {
> > +		put_device(dev);
> > +		return ret;
> > +	}
> 
> This looks like a race condition.

Really?  How?

> > +	ret = typec_register_altmodes(dev, partner->alt_modes);
> > +	if (ret) {
> > +		device_unregister(dev);
> > +		return ret;
> > +	}
> > +
> > +	/* REVISIT: Creating symlink for the port device for now. */
> > +	ret = sysfs_create_link(&port->dev.kobj, &dev->kobj, "partner");
> > +	if (ret)
> > +		dev_WARN(&port->dev, "failed to create link to %s (%d)\n",
> > +			 dev_name(dev), ret);
> 
> The attributes should be present as soon as the device is announced.

Yes, this is wrong and racy (hint, if you have to drop down to a sysfs
call within a driver, almost always something is wrong...)

thanks,

greg k-h