Messages in this thread Patch in this message | | | Date | Tue, 25 Jan 2005 02:32:51 -0500 | From | Mike Waychison <> | Subject | Re: [PATCH] fix bad locking in drivers/base/driver.c |
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Greg KH wrote: > On Mon, Jan 24, 2005 at 07:25:19PM +0100, Jirka Kosina wrote: > >>Hi, >> >>there has been (for quite some time) a bug in function driver_unregister() >>- the lock/unlock sequence is protecting nothing and the actual >>bus_remove_driver() is called outside critical section. >> >>Please apply. > > > No, please read the comment in the code about why this is the way it is. > The code is correct as is. >
Why don't we clean this up as in the proposed attached patch (against 2.6.10). Compile-tested only.
- -- Mike Waychison Sun Microsystems, Inc. 1 (650) 352-5299 voice 1 (416) 202-8336 voice
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NOTICE: The opinions expressed in this email are held by me, and may not represent the views of Sun Microsystems, Inc. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.5 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org
iD8DBQFB9fYjdQs4kOxk3/MRAgzrAJ96+aEawx/A0Sf0d5HqArsasgYrqQCZAVzp wuGctEJpxqtxezPD7LNGS+U= =77WW -----END PGP SIGNATURE----- Get rid of semaphore abuse by converting device_driver->unload_sem semaphore to device_driver->unloaded completion.
This should get rid of any confusion as well as save a few bytes in the process.
Signed-off-by: Mike Waychison <michael.waychison@sun.com> ---
drivers/base/bus.c | 2 +- drivers/base/driver.c | 13 ++++++------- include/linux/device.h | 2 +- 3 files changed, 8 insertions(+), 9 deletions(-)
Index: linux-2.6.10/drivers/base/bus.c =================================================================== --- linux-2.6.10.orig/drivers/base/bus.c 2004-12-24 16:34:26.000000000 -0500 +++ linux-2.6.10/drivers/base/bus.c 2005-01-25 02:14:10.000000000 -0500 @@ -65,7 +65,7 @@ static struct sysfs_ops driver_sysfs_ops static void driver_release(struct kobject * kobj) { struct device_driver * drv = to_driver(kobj); - up(&drv->unload_sem); + complete(&drv->unloaded); } static struct kobj_type ktype_driver = { Index: linux-2.6.10/drivers/base/driver.c =================================================================== --- linux-2.6.10.orig/drivers/base/driver.c 2004-12-24 16:35:25.000000000 -0500 +++ linux-2.6.10/drivers/base/driver.c 2005-01-25 02:16:31.000000000 -0500 @@ -79,14 +79,14 @@ void put_driver(struct device_driver * d * since most of the things we have to do deal with the bus * structures. * - * The one interesting aspect is that we initialize @drv->unload_sem - * to a locked state here. It will be unlocked when the driver - * reference count reaches 0. + * The one interesting aspect is that we setup @drv->unloaded + * as a completion that gets complete when the driver reference + * count reaches 0. */ int driver_register(struct device_driver * drv) { INIT_LIST_HEAD(&drv->devices); - init_MUTEX_LOCKED(&drv->unload_sem); + init_completion(&drv->unloaded); return bus_add_driver(drv); } @@ -97,7 +97,7 @@ int driver_register(struct device_driver * * Again, we pass off most of the work to the bus-level call. * - * Though, once that is done, we attempt to take @drv->unload_sem. + * Though, once that is done, we wait until @drv->unloaded is copmleted. * This will block until the driver refcount reaches 0, and it is * released. Only modular drivers will call this function, and we * have to guarantee that it won't complete, letting the driver @@ -107,8 +107,7 @@ int driver_register(struct device_driver void driver_unregister(struct device_driver * drv) { bus_remove_driver(drv); - down(&drv->unload_sem); - up(&drv->unload_sem); + wait_for_completion(&drv->unloaded); } /** Index: linux-2.6.10/include/linux/device.h =================================================================== --- linux-2.6.10.orig/include/linux/device.h 2004-12-24 16:35:28.000000000 -0500 +++ linux-2.6.10/include/linux/device.h 2005-01-25 02:13:13.716384240 -0500 @@ -102,7 +102,7 @@ struct device_driver { char * name; struct bus_type * bus; - struct semaphore unload_sem; + struct completion unloaded; struct kobject kobj; struct list_head devices; | |