2013-04-08 15:06:55

by Hector Palacios

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

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 <[email protected]>
---

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

2013-04-08 15:16:51

by Guenter Roeck

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

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 <[email protected]>

Reviewed-by: Guenter Roeck <[email protected]>

> ---
>
> 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
>
>

2013-05-26 16:51:42

by Wim Van Sebroeck

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

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 <[email protected]>
> ---
>
> 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.