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SubjectRe: [PATCH RFC] watchdog: core: don't try to stop device if not running
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@digi.com>
>>>
>>> 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
--
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