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Message-ID: <CAH9JG2WEQ4hzvd=Lunfi=Y7LYF19Gs0CNT3WACCxNT1EvzhoyA@mail.gmail.com>
Date: Wed, 25 Jan 2012 11:56:41 +0900
From: Kyungmin Park <kyungmin.park@...sung.com>
To: Alan Stern <stern@...land.harvard.edu>
Cc: Greg KH <greg@...ah.com>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Andy Walls <awalls@...metrocast.net>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
linux-input@...r.kernel.org, linux-media@...r.kernel.org,
linux-s390@...r.kernel.org,
Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] Driver core: driver_find() drops reference before returning
For s5p-{fimc,tv}
Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
On 1/25/12, Alan Stern <stern@...land.harvard.edu> wrote:
> 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@...land.harvard.edu>
> CC: Dmitry Torokhov <dmitry.torokhov@...il.com>
> CC: Kyungmin Park <kyungmin.park@...sung.com>
> CC: Andy Walls <awalls@...metrocast.net>
> CC: Martin Schwidefsky <schwidefsky@...ibm.com>
>
> ---
>
> drivers/base/driver.c | 7 +++++--
> drivers/input/gameport/gameport.c | 1 -
> drivers/input/serio/serio.c | 1 -
> drivers/media/video/cx18/cx18-alsa-main.c | 1 -
> drivers/media/video/ivtv/ivtvfb.c | 2 --
> drivers/media/video/s5p-fimc/fimc-mdevice.c | 5 +----
> drivers/media/video/s5p-tv/mixer_video.c | 1 -
> drivers/s390/net/smsgiucv_app.c | 9 ++++-----
> 8 files changed, 10 insertions(+), 17 deletions(-)
>
> Index: usb-3.3/drivers/base/driver.c
> ===================================================================
> --- usb-3.3.orig/drivers/base/driver.c
> +++ usb-3.3/drivers/base/driver.c
> @@ -234,7 +234,6 @@ int driver_register(struct device_driver
>
> 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
> struct driver_private *priv;
>
> if (k) {
> + /* Drop reference added by kset_find_obj() */
> + kobject_put(k);
> priv = to_driver(k);
> return priv->driver;
> }
> Index: usb-3.3/drivers/input/gameport/gameport.c
> ===================================================================
> --- usb-3.3.orig/drivers/input/gameport/gameport.c
> +++ usb-3.3/drivers/input/gameport/gameport.c
> @@ -449,7 +449,6 @@ static ssize_t gameport_rebind_driver(st
> } 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;
> }
> Index: usb-3.3/drivers/input/serio/serio.c
> ===================================================================
> --- usb-3.3.orig/drivers/input/serio/serio.c
> +++ usb-3.3/drivers/input/serio/serio.c
> @@ -441,7 +441,6 @@ static ssize_t serio_rebind_driver(struc
> } 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;
> Index: usb-3.3/drivers/media/video/cx18/cx18-alsa-main.c
> ===================================================================
> --- usb-3.3.orig/drivers/media/video/cx18/cx18-alsa-main.c
> +++ usb-3.3/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");
> Index: usb-3.3/drivers/media/video/ivtv/ivtvfb.c
> ===================================================================
> --- usb-3.3.orig/drivers/media/video/ivtv/ivtvfb.c
> +++ usb-3.3/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);
> Index: usb-3.3/drivers/media/video/s5p-fimc/fimc-mdevice.c
> ===================================================================
> --- usb-3.3.orig/drivers/media/video/s5p-fimc/fimc-mdevice.c
> +++ usb-3.3/drivers/media/video/s5p-fimc/fimc-mdevice.c
> @@ -344,16 +344,13 @@ static int fimc_md_register_platform_ent
> 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;
> }
>
> Index: usb-3.3/drivers/media/video/s5p-tv/mixer_video.c
> ===================================================================
> --- usb-3.3.orig/drivers/media/video/s5p-tv/mixer_video.c
> +++ usb-3.3/drivers/media/video/s5p-tv/mixer_video.c
> @@ -58,7 +58,6 @@ static struct v4l2_subdev *find_and_regi
> }
>
> done:
> - put_driver(drv);
> return sd;
> }
>
> Index: usb-3.3/drivers/s390/net/smsgiucv_app.c
> ===================================================================
> --- usb-3.3.orig/drivers/s390/net/smsgiucv_app.c
> +++ usb-3.3/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);
>
> --
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