On Wed, 22 Feb 2006, Greg KH wrote:
> > Index: usb-2.6/drivers/base/dd.c
> > ===================================================================
> > --- usb-2.6.orig/drivers/base/dd.c
> > +++ usb-2.6/drivers/base/dd.c
> > @@ -72,6 +72,8 @@ int driver_probe_device(struct device_dr
> > {
> > int ret = 0;
> >
> > + if (!device_is_registered(dev))
> > + return -ENODEV;
> > if (drv->bus->match && !drv->bus->match(dev, drv))
> > goto Done;
> >
> > Index: usb-2.6/drivers/base/bus.c
> > ===================================================================
> > --- usb-2.6.orig/drivers/base/bus.c
> > +++ usb-2.6/drivers/base/bus.c
> > @@ -367,6 +367,7 @@ int bus_add_device(struct device * dev)
> >
> > if (bus) {
> > pr_debug("bus %s: add device %s\n", bus->name, dev->bus_id);
> > + dev->is_registered = 1;
> > device_attach(dev);
> > klist_add_tail(&dev->knode_bus, &bus->klist_devices);
> > error = device_add_attrs(bus, dev);
> > @@ -393,7 +394,8 @@ void bus_remove_device(struct device * d
> > sysfs_remove_link(&dev->kobj, "bus");
> > sysfs_remove_link(&dev->bus->devices.kobj, dev->bus_id);
> > device_remove_attrs(dev->bus, dev);
> > - klist_remove(&dev->knode_bus);
> > + klist_del(&dev->knode_bus);
> > + dev->is_registered = 0;
>
> Don't we have a race between these two lines? How is that protected?
Are you referring to the two lines that set dev->is_registered? There is
no direct protection. However, one line is in bus_add_device() and the
other is in bus_remove_device(); I've been assuming that any code
responsible for adding and removing devices is serialized. That is, it
won't ever try to remove a device before that device has been completely
added.
If that assumption isn't true, there are undoubtedly many other similar
problems throughout the driver core. Like the calls to sysfs_create_link
in bus_add_device and sysfs_remove_link in bus_remove_device.
Or maybe you're referring to the device_is_registered() test in
driver_probe_device(). That's synchronized with the call to
device_release_driver() in bus_remove_device(), just below the portion you
quoted, because both routines hold dev->sem. So even if the probe routine
fails to see that the device has been unregistered, we are guaranteed that
device_release_driver will unbind the device.
If you're referring to two other lines, which lines are they?
Alan Stern
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