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

[Hector Palacios]

On 04/08/2013 10:16 AM, Guenter Roeck wrote:
> On Mon, Apr 08, 2013 at 09:48:57AM +0200, Hector Palacios wrote:
> > On 04/05/2013 08:34 PM, Guenter Roeck wrote:
> > > On Fri, Apr 05, 2013 at 06:09:44PM +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>
> > >
> > > How about the following patch instead ?
> > >
> > > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> > > index 08b48bb..9775e8d 100644
> > > --- a/drivers/watchdog/watchdog_dev.c
> > > +++ b/drivers/watchdog/watchdog_dev.c
> > > @@ -469,7 +469,9 @@ 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) ||
> > > +	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);
> > >
> > > Much less invasive and the result is the same.
> >
> > I like the simplicity but it is kind of inverted logic to initially
> > define err = -EBUSY only to turn it to zero later, so I'm rebuilding
> > your approach like this:
> >
> > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> > index ef8edec..a4163cd 100644
> > --- a/drivers/watchdog/watchdog_dev.c
> > +++ b/drivers/watchdog/watchdog_dev.c
> > @@ -463,16 +463,19 @@ 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);
> > +       }
>
> Ok, but the added { } are unnecessary and violate coding style rules.

Oops. Remainders of a debug message. Thanks for pointing out.

--
Héctor Palacios
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/