On 11/18/2015 01:02 PM, Damien Riegel wrote:
Many watchdog drivers register a reboot notifier in order to stop the
watchdog on system reboot. Thus we can factorize this code in the
watchdog core.
For that purpose, a new notifier block is added in watchdog_device for
internal use only, as well as a new watchdog_stop_on_reboot helper
function.
If this helper is called, watchdog core registers the related notifier
block and will stop the watchdog when SYS_HALT or SYS_DOWN is received.
Since this operation can be critical on some platforms, abort the device
registration if the reboot notifier registration fails.
Hi Damien,
Good idea. Couple of comments below.
Thanks,
Guenter
Suggested-by: Vivien Didelot <vivien.didelot@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Damien Riegel <damien.riegel@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Vivien Didelot <vivien.didelot@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/watchdog/watchdog-kernel-api.txt | 8 ++++++
drivers/watchdog/watchdog_core.c | 35 ++++++++++++++++++++++++++
include/linux/watchdog.h | 9 +++++++
3 files changed, 52 insertions(+)
diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index dbc6a65..0a37da7 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -53,6 +53,7 @@ struct watchdog_device {
unsigned int timeout;
unsigned int min_timeout;
unsigned int max_timeout;
+ struct notifier_block reboot_nb;
struct notifier_block restart_nb;
void *driver_data;
struct mutex lock;
@@ -76,6 +77,9 @@ It contains following fields:
* timeout: the watchdog timer's timeout value (in seconds).
* min_timeout: the watchdog timer's minimum timeout value (in seconds).
* max_timeout: the watchdog timer's maximum timeout value (in seconds).
+* reboot_nb: notifier block that is registered for reboot notifications, for
+ internal use only. If the driver calls watchdog_stop_on_reboot, watchdog core
+ will stop the watchdog on such notifications.
* restart_nb: notifier block that is registered for machine restart, for
internal use only. If a watchdog is capable of restarting the machine, it
should define ops->restart. Priority can be changed through
@@ -240,6 +244,10 @@ to set the default timeout value as timeout value in the watchdog_device and
then use this function to set the user "preferred" timeout value.
This routine returns zero on success and a negative errno code for failure.
+To disable the watchdog on reboot, the user must call the following helper:
+
+static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd);
+
To change the priority of the restart handler the following helper should be
used:
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 28dc901..2d49f8d 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -138,6 +138,23 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
}
EXPORT_SYMBOL_GPL(watchdog_init_timeout);
+static int watchdog_reboot_notifier(struct notifier_block *nb,
+ unsigned long code, void *data)
+{
+ struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
+ reboot_nb);
+
+ if (code == SYS_DOWN || code == SYS_HALT) {
+ int ret;
+
+ ret = wdd->ops->stop(wdd);
Nitpick, maybe, but only stop if running ?
Maybe that isn't a problem, but I am a bit concerned about side
effects of trying to stop a watchdog which isn't running.
+ if (ret)
+ return NOTIFY_BAD;
+ }
+
+ return NOTIFY_DONE;
+}
+
static int watchdog_restart_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
@@ -238,6 +255,21 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
return ret;
}
+ if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
+ wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
+
+ ret = register_reboot_notifier(&wdd->reboot_nb);
+ if (ret) {
+ dev_err(wdd->dev, "Cannot register reboot notifier (%d)\n",
+ ret);
+ watchdog_dev_unregister(wdd);
+ device_destroy(watchdog_class, devno);
+ ida_simple_remove(&watchdog_ida, wdd->id);
+ wdd->dev = NULL;
+ return ret;
At some point this really asks for a proper error handler in this function.
Separate patch, though.
+ }
+ }
+
if (wdd->ops->restart) {
wdd->restart_nb.notifier_call = watchdog_restart_notifier;
@@ -286,6 +318,9 @@ static void __watchdog_unregister_device(struct watchdog_device *wdd)
if (wdd->ops->restart)
unregister_restart_handler(&wdd->restart_nb);
+ if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
+ unregister_reboot_notifier(&wdd->reboot_nb);
+
devno = wdd->cdev.dev;
ret = watchdog_dev_unregister(wdd);
if (ret)
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 5b52c83..a88f955 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -65,6 +65,7 @@ struct watchdog_ops {
* @timeout: The watchdog devices timeout value (in seconds).
* @min_timeout:The watchdog devices minimum timeout value (in seconds).
* @max_timeout:The watchdog devices maximum timeout value (in seconds).
+ * @reboot_nb: The notifier block to stop watchdog on reboot.
* @restart_nb: The notifier block to register a restart function.
* @driver-data:Pointer to the drivers private data.
* @lock: Lock for watchdog core internal use only.
@@ -92,6 +93,7 @@ struct watchdog_device {
unsigned int timeout;
unsigned int min_timeout;
unsigned int max_timeout;
+ struct notifier_block reboot_nb;
struct notifier_block restart_nb;
void *driver_data;
struct mutex lock;
@@ -102,6 +104,7 @@ struct watchdog_device {
#define WDOG_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
#define WDOG_NO_WAY_OUT 3 /* Is 'nowayout' feature set ? */
#define WDOG_UNREGISTERED 4 /* Has the device been unregistered */
+#define WDOG_STOP_ON_REBOOT 5 /* Should be stopped on reboot */
struct list_head deferred;
};
@@ -121,6 +124,12 @@ static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool noway
set_bit(WDOG_NO_WAY_OUT, &wdd->status);
}
+/* Use the following function to stop the watchdog on reboot */
+static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd)
+{
+ set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
+}
+
/* Use the following function to check if a timeout value is invalid */
static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigned int t)
{
--
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