watchdog: core: add option to avoid early handling of watchdog

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@collabora.co.uk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 2696493c808b6d691250ae11c6392bf64708ad57..e9da196279149bfc363ee2adac4150e5eb7d92a1 100644 (file)
--- 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.
+
 config WATCHDOG_SYSFS
        bool "Read different watchdog information through sysfs"
        help

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index d5d2bbd8f428565357bb6e2f44be6adc9fa84701..4bc7ab60b12c4e9b3ec78db03723f5d13cbc52a0 100644 (file)
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -80,6 +80,9 @@ static struct watchdog_core_data *old_wd_data;
 
 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 */
@@ -956,9 +959,14 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
         * and schedule an immediate ping.
         */
        if (watchdog_hw_running(wdd)) {
-               __module_get(wdd->ops->owner);
-               kref_get(&wd_data->kref);
-               queue_delayed_work(watchdog_wq, &wd_data->work, 0);
+               if (handle_boot_enabled) {
+                       __module_get(wdd->ops->owner);
+                       kref_get(&wd_data->kref);
+                       queue_delayed_work(watchdog_wq, &wd_data->work, 0);
+               } else {
+                       pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
+                                       wdd->id);
+               }
        }
 
        return 0;
@@ -1106,3 +1114,8 @@ void __exit watchdog_dev_exit(void)
        class_unregister(&watchdog_class);
        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)) ")");