From: Sebastian Reichel <sebastian.reichel@...>

commit 2501b015313fe2fa40ed11fa4dd1748e09b7c773 upstream.

On some systems its desirable to have watchdog reboot the system
when it does not come up fast enough. This adds a kernel parameter
to disable the auto-update of watchdog before userspace takes over
and a kernel option to set the default. The info messages were
added to shorten error searching on misconfigured systems.

Signed-off-by: Sebastian Reichel <sebastian.reichel@...>
Reviewed-by: Guenter Roeck <linux@...>
Signed-off-by: Guenter Roeck <linux@...>
Signed-off-by: Wim Van Sebroeck <wim@...>
[mosipov@... backported to 4.4.y]
Signed-off-by: Maxim Yu. Osipov <mosipov@...>
---
drivers/watchdog/Kconfig | 11 +++++++++++
drivers/watchdog/watchdog_dev.c | 21 +++++++++++++++++----
2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 1c427beffadd..88743cd0a7e6 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -46,6 +46,17 @@ config WATCHDOG_NOWAYOUT
get killed. If you say Y here, the watchdog cannot be stopped once
it has been started.

+config WATCHDOG_HANDLE_BOOT_ENABLED
+ bool "Update boot-enabled watchdog until userspace takes over"
+ default y
+ help
+ The default watchdog behaviour (which you get if you say Y here) is
+ to ping watchdog devices that were enabled before the driver has
+ been loaded until control is taken over from userspace using the
+ /dev/watchdog file. If you say N here, the kernel will not update
+ the watchdog on its own. Thus if your userspace does not start fast
+ enough your device will reboot.
+
#
# General Watchdog drivers
#
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 1edc3d78636b..8ca87ae467f2 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -53,6 +53,9 @@ static struct watchdog_device *old_wdd;

static struct workqueue_struct *watchdog_wq;

+static bool handle_boot_enabled =
+ IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
+
static inline bool watchdog_need_worker(struct watchdog_device *wdd)
{
/* All variables in milli-seconds */
@@ -683,10 +686,15 @@ int watchdog_dev_register(struct watchdog_device *wdd)
* and schedule an immediate ping.
*/
if (watchdog_hw_running(wdd)) {
- __module_get(wdd->ops->owner);
- if (wdd->ops->ref)
- wdd->ops->ref(wdd);
- queue_delayed_work(watchdog_wq, &wdd->work, 0);
+ if (handle_boot_enabled) {
+ __module_get(wdd->ops->owner);
+ if (wdd->ops->ref)
+ wdd->ops->ref(wdd);
+ queue_delayed_work(watchdog_wq, &wdd->work, 0);
+ } else {
+ pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
+ wdd->id);
+ }
}

return 0;
@@ -756,3 +764,8 @@ void __exit watchdog_dev_exit(void)
unregister_chrdev_region(watchdog_devt, MAX_DOGS);
destroy_workqueue(watchdog_wq);
}
+
+module_param(handle_boot_enabled, bool, 0444);
+MODULE_PARM_DESC(handle_boot_enabled,
+ "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
+ __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
--
2.11.0