On 04/22/2015 01:11 PM, Timo Kokkonen wrote:
> There is a great deal of diversity in the watchdog hardware found on
> different devices. Differen hardware have different contstraints on
> them, many of the constraints that are excessively difficult for the
> user space to satisfy.
>
> One such constraint is the length of the timeout value, which in many
> cases can be just a few seconds. Drivers are creating ad hoc solutions
> with timers and workqueues to extend the timeout in order to give user
> space more time between updates. Looking at the drivers it is clear
> that this has resulted to a lot of duplicate code.
>
> Add an extension to the watchdog kernel API that allows the driver to
> describe tis HW constraints to the watchdog code. A kernel worker in
> the core is then used to extend the watchdog timeout on behalf of the
> user space. This allows the drivers to be simplified as core takes
> over the timer extending.
>
> Tested-by: Wenyou Yang <wenyou.yang@xxxxxxxxx>
> Signed-off-by: Timo Kokkonen <timo.kokkonen@xxxxxxxxxx>
> ---
> drivers/watchdog/watchdog_core.c | 101 +++++++++++++++++++++++++++++++++++++--
> drivers/watchdog/watchdog_dev.c | 75 ++++++++++++++++++++++++++---
> include/linux/watchdog.h | 23 +++++++++
> 3 files changed, 189 insertions(+), 10 deletions(-)
>
[...]
> static int watchdog_set_timeout(struct watchdog_device *wddev,
> unsigned int timeout)
> {
> - int err;
> + int err = 0;
> +
> + if (wddev->hw_max_timeout) {
> + int hw_timeout;
> + /*
> + * We can't support too short timeout values. There is
> + * really no maximu however, anything longer than HW
> + * maximum will be supported by the watchdog core on
> + * behalf of the actual HW.
> + */
> + if (timeout < wddev->min_timeout)
> + return -EINVAL;
> +
> + mutex_lock(&wddev->lock);
The locking in this function looks weird.
> + if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
> + err = -ENODEV;
> + goto out_timeout;
> + }
> +
> + if (timeout * HZ > wddev->hw_max_timeout)
> + schedule_delayed_work(&wddev->work,
> + wddev->hw_heartbeat);
> +
> + hw_timeout = min(timeout, wddev->hw_max_timeout / HZ);
> + if (wddev->info->options & WDIOF_SETTIMEOUT)
> + err = wddev->ops->set_timeout(wddev, hw_timeout);
> +
> + if (hw_timeout < timeout)
> + wddev->timeout = timeout;
> +
> + goto out_timeout;
> + }
>
> if ((wddev->ops->set_timeout == NULL) ||
> !(wddev->info->options & WDIOF_SETTIMEOUT))
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
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