> @@ -101,6 +96,28 @@
> drv->release(drv);
> }
>
> +void remove_driver(struct device_driver * drv)
> +{
> + spin_lock(&device_lock);
> + atomic_set(&drv->refcount,0);
> + spin_unlock(&device_lock);
> + __remove_driver(drv);
> +}
> @@ -124,7 +136,7 @@
> void
> pci_unregister_driver(struct pci_driver *drv)
> {
> - put_driver(&drv->driver);
> + remove_driver(&drv->driver);
> }
>
> static struct pci_driver pci_compat_driver = {
Now does that mean you have given up on getting the ref counting right?
Forcing the ref count to zero is obviously not a solution,
pci_unregister_driver is usually called at module unload time, which means
that struct pci_driver will go away immediately after the call returns. If
you know that there are no other users at this time (which I doubt), you
don't need to do the whole refcounting thing at all (since at all times
before the ref count is surely >= 1). If not, you're racy.
I think I brought up that issue before, though nobody seemed interested.
AFAICS there are two possible solutions:
o provide a destructor callback which is called from put_driver when we're
about to throw away the last reference which would let whoever registered
the thing in the beginning know that it's all his again now (If it was
kmalloced, that would be the time to kfree it). In this case it's
rather that the callback would tell us we can now finish
module_exit().
o Use a completion or something and do the above inside
pci_unregister_driver (or remove_driver). I.e. have it sleep until
all references are gone. That would fix the race for the typical
void my_module_exit(void) { pci_unregister_driver(&my_driver); }
case.
(The latter would be my preference, as I see no point in having driver
authors deal with the complication of waiting for completion of
pci_unregister_driver() themselves)
--Kai
-
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This archive was generated by hypermail 2b29 : Fri Jun 07 2002 - 22:00:26 EST