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authorAlan Stern <stern@rowland.harvard.edu>2012-01-24 13:34:24 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2012-01-24 16:00:34 -0800
commitfde25a9b63b9a3dc91365c394a426ebe64cfc2da (patch)
treeecc24bd2702cb7cb32cd4d22729541d5c79cee39 /drivers/base/driver.c
parent2b31594a9523449b168946725689d039c80204de (diff)
downloadlinux-fde25a9b63b9a3dc91365c394a426ebe64cfc2da.tar.bz2
Driver core: driver_find() drops reference before returning
As part of the removal of get_driver()/put_driver(), this patch (as1510) changes driver_find(); it now drops the reference it acquires before returning. The patch also adjusts all the callers of driver_find() to remove the now unnecessary calls to put_driver(). In addition, the patch adds a warning to driver_find(): Callers must make sure the driver they are searching for does not get unloaded while they are using it. This has always been the case; driver_find() has never prevented a driver from being unregistered or unloaded. Hence the patch will not introduce any new bugs. The existing callers all seem to be okay in this respect, however I don't understand the video drivers well enough to be certain about them. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Dmitry Torokhov <dmitry.torokhov@gmail.com> CC: Kyungmin Park <kyungmin.park@samsung.com> CC: Andy Walls <awalls@md.metrocast.net> CC: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/base/driver.c')
-rw-r--r--drivers/base/driver.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index b631f7c59453..e979cad75c6e 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -234,7 +234,6 @@ int driver_register(struct device_driver *drv)
other = driver_find(drv->name, drv->bus);
if (other) {
- put_driver(other);
printk(KERN_ERR "Error: Driver '%s' is already registered, "
"aborting...\n", drv->name);
return -EBUSY;
@@ -275,7 +274,9 @@ EXPORT_SYMBOL_GPL(driver_unregister);
* Call kset_find_obj() to iterate over list of drivers on
* a bus to find driver by name. Return driver if found.
*
- * Note that kset_find_obj increments driver's reference count.
+ * This routine provides no locking to prevent the driver it returns
+ * from being unregistered or unloaded while the caller is using it.
+ * The caller is responsible for preventing this.
*/
struct device_driver *driver_find(const char *name, struct bus_type *bus)
{
@@ -283,6 +284,8 @@ struct device_driver *driver_find(const char *name, struct bus_type *bus)
struct driver_private *priv;
if (k) {
+ /* Drop reference added by kset_find_obj() */
+ kobject_put(k);
priv = to_driver(k);
return priv->driver;
}