From: Alan Stern Date: Tue, 24 Jan 2012 18:34:24 +0000 (-0500) Subject: Driver core: driver_find() drops reference before returning X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=fde25a9b63b9a3dc91365c394a426ebe64cfc2da;p=linux-beck.git 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 --- 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; } diff --git a/drivers/input/gameport/gameport.c b/drivers/input/gameport/gameport.c index c351aa421f8f..da739d9d1905 100644 --- a/drivers/input/gameport/gameport.c +++ b/drivers/input/gameport/gameport.c @@ -449,7 +449,6 @@ static ssize_t gameport_rebind_driver(struct device *dev, struct device_attribut } else if ((drv = driver_find(buf, &gameport_bus)) != NULL) { gameport_disconnect_port(gameport); error = gameport_bind_driver(gameport, to_gameport_driver(drv)); - put_driver(drv); } else { error = -EINVAL; } diff --git a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c index ba70058e2be3..d0f7533dbf88 100644 --- a/drivers/input/serio/serio.c +++ b/drivers/input/serio/serio.c @@ -441,7 +441,6 @@ static ssize_t serio_rebind_driver(struct device *dev, struct device_attribute * } else if ((drv = driver_find(buf, &serio_bus)) != NULL) { serio_disconnect_port(serio); error = serio_bind_driver(serio, to_serio_driver(drv)); - put_driver(drv); serio_remove_duplicate_events(serio, SERIO_RESCAN_PORT); } else { error = -EINVAL; diff --git a/drivers/media/video/cx18/cx18-alsa-main.c b/drivers/media/video/cx18/cx18-alsa-main.c index a1e6c2a32478..e118361c2e7b 100644 --- a/drivers/media/video/cx18/cx18-alsa-main.c +++ b/drivers/media/video/cx18/cx18-alsa-main.c @@ -285,7 +285,6 @@ static void __exit cx18_alsa_exit(void) drv = driver_find("cx18", &pci_bus_type); ret = driver_for_each_device(drv, NULL, NULL, cx18_alsa_exit_callback); - put_driver(drv); cx18_ext_init = NULL; printk(KERN_INFO "cx18-alsa: module unload complete\n"); diff --git a/drivers/media/video/ivtv/ivtvfb.c b/drivers/media/video/ivtv/ivtvfb.c index d0fbfcf7133d..e5e7fa9e737b 100644 --- a/drivers/media/video/ivtv/ivtvfb.c +++ b/drivers/media/video/ivtv/ivtvfb.c @@ -1293,7 +1293,6 @@ static int __init ivtvfb_init(void) drv = driver_find("ivtv", &pci_bus_type); err = driver_for_each_device(drv, NULL, ®istered, ivtvfb_callback_init); - put_driver(drv); if (!registered) { printk(KERN_ERR "ivtvfb: no cards found\n"); return -ENODEV; @@ -1310,7 +1309,6 @@ static void ivtvfb_cleanup(void) drv = driver_find("ivtv", &pci_bus_type); err = driver_for_each_device(drv, NULL, NULL, ivtvfb_callback_cleanup); - put_driver(drv); } module_init(ivtvfb_init); diff --git a/drivers/media/video/s5p-fimc/fimc-mdevice.c b/drivers/media/video/s5p-fimc/fimc-mdevice.c index 8ea4ee116e46..63eccb55728f 100644 --- a/drivers/media/video/s5p-fimc/fimc-mdevice.c +++ b/drivers/media/video/s5p-fimc/fimc-mdevice.c @@ -344,16 +344,13 @@ static int fimc_md_register_platform_entities(struct fimc_md *fmd) return -ENODEV; ret = driver_for_each_device(driver, NULL, fmd, fimc_register_callback); - put_driver(driver); if (ret) return ret; driver = driver_find(CSIS_DRIVER_NAME, &platform_bus_type); - if (driver) { + if (driver) ret = driver_for_each_device(driver, NULL, fmd, csis_register_callback); - put_driver(driver); - } return ret; } diff --git a/drivers/media/video/s5p-tv/mixer_video.c b/drivers/media/video/s5p-tv/mixer_video.c index 7884baeff76a..f7ca5cc143c6 100644 --- a/drivers/media/video/s5p-tv/mixer_video.c +++ b/drivers/media/video/s5p-tv/mixer_video.c @@ -58,7 +58,6 @@ static struct v4l2_subdev *find_and_register_subdev( } done: - put_driver(drv); return sd; } diff --git a/drivers/s390/net/smsgiucv_app.c b/drivers/s390/net/smsgiucv_app.c index 4d2ea4000422..32515a201bbc 100644 --- a/drivers/s390/net/smsgiucv_app.c +++ b/drivers/s390/net/smsgiucv_app.c @@ -168,7 +168,7 @@ static int __init smsgiucv_app_init(void) rc = dev_set_name(smsg_app_dev, KMSG_COMPONENT); if (rc) { kfree(smsg_app_dev); - goto fail_put_driver; + goto fail; } smsg_app_dev->bus = &iucv_bus; smsg_app_dev->parent = iucv_root; @@ -177,7 +177,7 @@ static int __init smsgiucv_app_init(void) rc = device_register(smsg_app_dev); if (rc) { put_device(smsg_app_dev); - goto fail_put_driver; + goto fail; } /* convert sender to uppercase characters */ @@ -191,12 +191,11 @@ static int __init smsgiucv_app_init(void) rc = smsg_register_callback(SMSG_PREFIX, smsg_app_callback); if (rc) { device_unregister(smsg_app_dev); - goto fail_put_driver; + goto fail; } rc = 0; -fail_put_driver: - put_driver(smsgiucv_drv); +fail: return rc; } module_init(smsgiucv_app_init);