Re: Driverfs updates

[Keith Owens <kaos@ocs.com.au>]

On Mon, 8 Jul 2002 11:41:52 -0700 (PDT), 
Patrick Mochel <mochel@osdl.org> wrote:
>- Add struct module * owner field to struct device_driver
>- Change {get,put}_driver to use it

struct device_driver * get_driver(struct device_driver * drv)
{
        if (drv && drv->owner)
                if (!try_inc_mod_count(drv->owner))
                        return NULL;
        return drv;
}

is racy.  The module can be unloaded after if (drv->owner) and before
try_inc_mod_count.  To prevent that race, drv itself must be locked
around calls to get_driver().

The "normal" method is to have a high level lock that controls the drv
list and to take that lock in the register and unregister routines and
around the call to try_inc_mod_count.  drv->bus->lock is no good,
anything that relies on reading drv without a lock or module reference
count is racy.  I suggest you add a global driverfs_lock.