On 05/11/2017 05:52 AM, Sebastian Reichel wrote:
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@xxxxxxxxxxxxxxx>
---
drivers/watchdog/Kconfig | 11 +++++++++++
drivers/watchdog/watchdog_dev.c | 16 ++++++++++++++++
2 files changed, 27 insertions(+)
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 52a70ee6014f..4e08b2b97941 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 "Disable watchdog shutdown on close"
Enable ?
+ 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 d5d2bbd8f428..5e6d6d4db82f 100644
--- 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 */
@@ -956,6 +959,14 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
* and schedule an immediate ping.
*/
if (watchdog_hw_running(wdd)) {
+ if (!handle_boot_enabled) {
+ pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
+ wdd->id);
+ return 0;
I don't like the immediate return here; if some other code is added further below,
it may miss this return. Something like
if (handle_boot_enabled) {
// do everything here
} else {
// print message
}
would be better.
+ }
+
+ pr_info("auto-update boot-enabled watchdog%d until userspace takes over\n",
+ wdd->id);
This message will add a lot of noise. If you really think it is useful please make it
a debug message.
__module_get(wdd->ops->owner);
kref_get(&wd_data->kref);
queue_delayed_work(watchdog_wq, &wd_data->work, 0);
@@ -1106,3 +1117,8 @@ 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)) ")");
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