Re: 2.6.30-rc6: Reported regressions from 2.6.29

Linus Torvalds
2009-05-17T02:15:49Z

On Sun, 17 May 2009, Kay Sievers wrote:
>
> This makes the oops in the driver-core, caused by the rtc driver
> unregister, go away. The original issue is also fixed in the rtc driver
> itself.

I don't think this is sufficient.

> --- a/drivers/base/driver.c
> +++ b/drivers/base/driver.c
> @@ -257,6 +257,8 @@ EXPORT_SYMBOL_GPL(driver_register);
> */
> void driver_unregister(struct device_driver *drv)
> {
> + if (!drv || !drv->p)
> + return;
> driver_remove_groups(drv, drv->groups);
> bus_remove_driver(drv);
> }

Ok, fine so far, but look at "driver_register()".

It will set drv->p, but then not unset it if it fails! (For a certain
class of failures)

So for a certain failure pattern, drv->p will point to some stale value.
Should we not clear drv->p in the "out_unregister" patch?

To confuse the thing more, there are actually "half-way failures" that
_succeed_ in driver registration, but then return an error code. See that
whole

kobject_uevent(&priv->kobj, KOBJ_ADD);
return error;

case in the "success" path driver_register(). We may return an error
despite the fact that we actually attached the driver to bus, but
"add_bind_files()" failed. A caller would be understandable very unhappy.

So I suspect we should do something like the appended (in addition to your
patch). Comments?

Linus
---

drivers/base/bus.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index dc030f1..dcd499d 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -700,8 +700,9 @@ int bus_add_driver(struct device_driver *drv)
}

kobject_uevent(&priv->kobj, KOBJ_ADD);
- return error;
+ return 0;
out_unregister:
+ drv->p = NULL;
kobject_put(&priv->kobj);
out_put_bus:
bus_put(bus);