[PATCH v3] watchdog: core: don't try to stop device if not running

[PATCH v3] watchdog: core: don't try to stop device if not running

[Hector Palacios]

A watchdog device may be stopped from userspace using WDIOC_SETOPTIONS
ioctl and flag WDIOS_DISABLECARD. If the device is closed after this
operation, watchdog_release() is called and status bits checked for
stopping it. Besides, if the device has not been unregistered a critical
message "watchdog did not stop!" is printed, although the ioctl may have
successfully stopped it already.

Without the patch a user application sample code like this will successfully
stop the watchdog, but the kernel will output the message
"watchdog did not stop!":

	wd_fd = open("/dev/watchdog", O_RDWR);

	flags = WDIOS_DISABLECARD;
	ioctl(wd_fd, WDIOC_SETOPTIONS, &flags);

	close(wd_fd);

Signed-off-by: Hector Palacios <hector.palacios@digi.com>
---

Changes from v1:
 - Make it less intrusive with 'if/else if' clauses.
 - Change the logic of 'err' variable for better readability of code.
 - Remove one-liner if brackets that broke coding sytle.
Changes from v2:
 - Revert "Change the logic of 'err'..." from v1 because otherwise the
   'else if' can't be reached if the watchdog is running.

 drivers/watchdog/watchdog_dev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index ef8edec..6117c48 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -470,8 +470,10 @@ static int watchdog_release(struct inode *inode, struct file *file)
 	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 	 * watchdog_stop will fail.
 	 */
-	if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
-	    !(wdd->info->options & WDIOF_MAGICCLOSE))
+	if (!test_bit(WDOG_ACTIVE, &wdd->status))
+		err = 0;
+	else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
+		 !(wdd->info->options & WDIOF_MAGICCLOSE))
 		err = watchdog_stop(wdd);
 
 	/* If the watchdog was not stopped, send a keepalive ping */
-- 
1.8.2

Re: [PATCH v3] watchdog: core: don't try to stop device if not running

[Guenter Roeck]

On Mon, Apr 08, 2013 at 05:06:32PM +0200, Hector Palacios wrote:
> A watchdog device may be stopped from userspace using WDIOC_SETOPTIONS
> ioctl and flag WDIOS_DISABLECARD. If the device is closed after this
> operation, watchdog_release() is called and status bits checked for
> stopping it. Besides, if the device has not been unregistered a critical
> message "watchdog did not stop!" is printed, although the ioctl may have
> successfully stopped it already.
> 
> Without the patch a user application sample code like this will successfully
> stop the watchdog, but the kernel will output the message
> "watchdog did not stop!":
> 
> 	wd_fd = open("/dev/watchdog", O_RDWR);
> 
> 	flags = WDIOS_DISABLECARD;
> 	ioctl(wd_fd, WDIOC_SETOPTIONS, &flags);
> 
> 	close(wd_fd);
> 
> Signed-off-by: Hector Palacios <hector.palacios@digi.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> 
> Changes from v1:
>  - Make it less intrusive with 'if/else if' clauses.
>  - Change the logic of 'err' variable for better readability of code.
>  - Remove one-liner if brackets that broke coding sytle.
> Changes from v2:
>  - Revert "Change the logic of 'err'..." from v1 because otherwise the
>    'else if' can't be reached if the watchdog is running.
> 
>  drivers/watchdog/watchdog_dev.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index ef8edec..6117c48 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -470,8 +470,10 @@ static int watchdog_release(struct inode *inode, struct file *file)
>  	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
>  	 * watchdog_stop will fail.
>  	 */
> -	if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
> -	    !(wdd->info->options & WDIOF_MAGICCLOSE))
> +	if (!test_bit(WDOG_ACTIVE, &wdd->status))
> +		err = 0;
> +	else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
> +		 !(wdd->info->options & WDIOF_MAGICCLOSE))
>  		err = watchdog_stop(wdd);
>  
>  	/* If the watchdog was not stopped, send a keepalive ping */
> -- 
> 1.8.2
> 
> 

Re: [PATCH v3] watchdog: core: don't try to stop device if not running

[Wim Van Sebroeck]

Hi Hector,

> A watchdog device may be stopped from userspace using WDIOC_SETOPTIONS
> ioctl and flag WDIOS_DISABLECARD. If the device is closed after this
> operation, watchdog_release() is called and status bits checked for
> stopping it. Besides, if the device has not been unregistered a critical
> message "watchdog did not stop!" is printed, although the ioctl may have
> successfully stopped it already.
> 
> Without the patch a user application sample code like this will successfully
> stop the watchdog, but the kernel will output the message
> "watchdog did not stop!":
> 
> 	wd_fd = open("/dev/watchdog", O_RDWR);
> 
> 	flags = WDIOS_DISABLECARD;
> 	ioctl(wd_fd, WDIOC_SETOPTIONS, &flags);
> 
> 	close(wd_fd);
> 
> Signed-off-by: Hector Palacios <hector.palacios@digi.com>
> ---
> 
> Changes from v1:
>  - Make it less intrusive with 'if/else if' clauses.
>  - Change the logic of 'err' variable for better readability of code.
>  - Remove one-liner if brackets that broke coding sytle.
> Changes from v2:
>  - Revert "Change the logic of 'err'..." from v1 because otherwise the
>    'else if' can't be reached if the watchdog is running.
> 
>  drivers/watchdog/watchdog_dev.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 

Patch added to linux-watchdog-next.

Kind regards,
Wim.