[PATCH 1/2] char: add WARN_ON() in misc_deregister()

[PATCH 1/2] char: add WARN_ON() in misc_deregister()

[Akinobu Mita]

misc_deregister() returns an error only when it attempts to unregister
the device that is not registered. This is the driver's bug.

Most of the drivers don't check the return value of misc_deregister().
(It is not bad thing because most of kernel *_unregister() API always
succeed and do not return value)

So it is better to indicate the error by WARN_ON() in misc_deregister().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 drivers/char/misc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index cd650ca..abdafd4 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -242,7 +242,7 @@ int misc_deregister(struct miscdevice *misc)
 {
 	int i = DYNAMIC_MINORS - misc->minor - 1;
 
-	if (list_empty(&misc->list))
+	if (WARN_ON(list_empty(&misc->list)))
 		return -EINVAL;
 
 	mutex_lock(&misc_mtx);
-- 
1.6.0.6

[PATCH 2/2] s390: remove WARN_ON for misc_deregister() failures

[Akinobu Mita]

The previous change added WARN_ON() in misc_deregister().
So it is not necessary to WARN_ON() misc_deregister() failure by
callers.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
---
 drivers/s390/block/dasd_eer.c |    2 +-
 drivers/s390/char/monreader.c |    2 +-
 drivers/s390/char/monwriter.c |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/block/dasd_eer.c b/drivers/s390/block/dasd_eer.c
index dd88803..7158f95 100644
--- a/drivers/s390/block/dasd_eer.c
+++ b/drivers/s390/block/dasd_eer.c
@@ -701,7 +701,7 @@ int __init dasd_eer_init(void)
 void dasd_eer_exit(void)
 {
 	if (dasd_eer_dev) {
-		WARN_ON(misc_deregister(dasd_eer_dev) != 0);
+		misc_deregister(dasd_eer_dev);
 		kfree(dasd_eer_dev);
 		dasd_eer_dev = NULL;
 	}
diff --git a/drivers/s390/char/monreader.c b/drivers/s390/char/monreader.c
index 2ed3f82..e021ec6 100644
--- a/drivers/s390/char/monreader.c
+++ b/drivers/s390/char/monreader.c
@@ -627,7 +627,7 @@ out_iucv:
 static void __exit mon_exit(void)
 {
 	segment_unload(mon_dcss_name);
-	WARN_ON(misc_deregister(&mon_dev) != 0);
+	misc_deregister(&mon_dev);
 	device_unregister(monreader_device);
 	driver_unregister(&monreader_driver);
 	iucv_unregister(&monreader_iucv_handler, 1);
diff --git a/drivers/s390/char/monwriter.c b/drivers/s390/char/monwriter.c
index 98a49df..572a1e7 100644
--- a/drivers/s390/char/monwriter.c
+++ b/drivers/s390/char/monwriter.c
@@ -380,7 +380,7 @@ out_driver:
 
 static void __exit mon_exit(void)
 {
-	WARN_ON(misc_deregister(&mon_dev) != 0);
+	misc_deregister(&mon_dev);
 	platform_device_unregister(monwriter_pdev);
 	platform_driver_unregister(&monwriter_pdrv);
 }
-- 
1.6.0.6