From fde25a9b63b9a3dc91365c394a426ebe64cfc2da Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Tue, 24 Jan 2012 13:34:24 -0500 Subject: 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 CC: Dmitry Torokhov CC: Kyungmin Park CC: Andy Walls CC: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- drivers/base/driver.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'drivers/base') 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; } -- cgit v1.2.3