Re: [PATCH v2] watchdog: core: don't try to stop device if not running

[Hector Palacios]

On 04/08/2013 03:41 PM, Guenter Roeck wrote:
> On Mon, Apr 08, 2013 at 11:10:58AM +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@xxxxxxxx>
> > ---
> >
> > 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
> >
> >   drivers/watchdog/watchdog_dev.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> > index ef8edec..8e0f1b8 100644
> > --- a/drivers/watchdog/watchdog_dev.c
> > +++ b/drivers/watchdog/watchdog_dev.c
> > @@ -463,15 +463,17 @@ out:
> >   static int watchdog_release(struct inode *inode, struct file *file)
> >   {
> >   	struct watchdog_device *wdd = file->private_data;
> > -	int err = -EBUSY;
> > +	int err = 0;
> >
> >   	/*
> >   	 * We only stop the watchdog if we received the magic character
> >   	 * 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 = -EBUSY;
> > +	else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
> > +		 !(wdd->info->options & WDIOF_MAGICCLOSE))
> >   		err = watchdog_stop(wdd);
> Looking at it again, it is now broken and fails with EBUSY if WDOG_ACTIVE is
> set, and it tries to stop the watchdog if it is already stopped.

You are right, good catch! So your patch version wins.
Thank you
--
Héctor Palacios
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