Some applications require to start watchdog before userspace software.
This patch enables such feature. Only the flag is necessary
to enable it.
Moreover kernel's ping is re-enabled when userspace software closed
watchdog using the magic character. The features improves kernel's
reliability if hardware watchdog is available.
Signed-off-by: Janusz Uzycki <j.uzycki@xxxxxxxxxxxxxx>
---
drivers/watchdog/watchdog_dev.c | 65 ++++++++++++++++++++++++++-
include/linux/watchdog.h | 4 ++
2 files changed, 68 insertions(+), 1 deletion(-)
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 6aaefba..afc14f7 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -41,6 +41,7 @@
#include <linux/miscdevice.h> /* For handling misc devices */
#include <linux/init.h> /* For __init/__exit/... */
#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
+#include <linux/jiffies.h> /* for ping timer */
#include "watchdog_core.h"
@@ -277,6 +278,60 @@ out_ioctl:
return err;
}
+static void watchdog_ping_timer_cb(unsigned long data)
+{
+ struct watchdog_device *wdd = (struct watchdog_device *)data;
+ watchdog_ping(wdd);
+ /* call next ping half the timeout value */
+ mod_timer(&wdd->ping_timer,
+ jiffies + msecs_to_jiffies(wdd->timeout * 500));
+}
+
+static void watchdog_timer_start(struct watchdog_device *wdd)
+{
+ /* TODO: watchdog_start():
+ * it should probably be handled by the caller, to let us separate
+ * cases where the watchdog is already running (for example on close). */
+ watchdog_start(wdd);
+ watchdog_ping_timer_cb((unsigned long)wdd);
+}
+
+static void watchdog_timer_stop(struct watchdog_device *wdd)
+{
+ del_timer_sync(&wdd->ping_timer);
+}
+
+static int watchdog_timer_restart(struct watchdog_device *wdd)
+{
+ if (test_bit(WDOG_KEEP_ON, &wdd->status)) {
+ watchdog_timer_start(wdd);
+ return 0;
+ }
+ return watchdog_stop(wdd);
+}
+
+static int watchdog_timer_register(struct watchdog_device *wdd)
+{
+ if (test_bit(WDOG_KEEP_ON, &wdd->status)) {
+ if (!try_module_get(wdd->ops->owner))
+ return -ENODEV;
+ setup_timer(&wdd->ping_timer, watchdog_ping_timer_cb,
+ (unsigned long)wdd);
+ watchdog_timer_start(wdd);
+ }
+ return 0;
+}
+
+static int watchdog_timer_unregister(struct watchdog_device *wdd)
+{
+ if (test_bit(WDOG_KEEP_ON, &wdd->status)) {
+ watchdog_timer_stop(wdd);
+ watchdog_stop(wdd);
+ module_put(wdd->ops->owner);
+ }
+ return 0;
+}
+
/*
* watchdog_write: writes to the watchdog.
* @file: file from VFS
@@ -430,6 +485,9 @@ static int watchdog_open(struct inode *inode, struct file *file)
if (!try_module_get(wdd->ops->owner))
goto out;
+ if (test_bit(WDOG_KEEP_ON, &wdd->status))
+ watchdog_timer_stop(wdd);
+
err = watchdog_start(wdd);
if (err < 0)
goto out_mod;
@@ -473,7 +531,7 @@ static int watchdog_release(struct inode *inode, struct file *file)
err = 0;
else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
!(wdd->info->options & WDIOF_MAGICCLOSE))
- err = watchdog_stop(wdd);
+ err = watchdog_timer_restart(wdd);
/* If the watchdog was not stopped, send a keepalive ping */
if (err < 0) {
@@ -553,7 +611,10 @@ int watchdog_dev_register(struct watchdog_device *watchdog)
misc_deregister(&watchdog_miscdev);
old_wdd = NULL;
}
+ return err;
}
+
+ err = watchdog_timer_register(watchdog);
return err;
}
@@ -575,6 +636,8 @@ int watchdog_dev_unregister(struct watchdog_device *watchdog)
misc_deregister(&watchdog_miscdev);
old_wdd = NULL;
}
+
+ watchdog_timer_unregister(watchdog);
return 0;
}
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 2a3038e..0afeabd 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -12,6 +12,7 @@
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/cdev.h>
+#include <linux/timer.h> /* for ping timer */
#include <uapi/linux/watchdog.h>
struct watchdog_ops;
@@ -95,6 +96,8 @@ 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_KEEP_ON 5 /* Is 'keep on' feature set? */
+ struct timer_list ping_timer; /* timer to keep on hardware ping */
};
#ifdef CONFIG_WATCHDOG_NOWAYOUT
@@ -104,6 +107,7 @@ struct watchdog_device {
#define WATCHDOG_NOWAYOUT 0
#define WATCHDOG_NOWAYOUT_INIT_STATUS 0
#endif
+#define WATCHDOG_KEEP_ON (1 << WDOG_KEEP_ON)
/* Use the following function to check whether or not the watchdog is active */
static inline bool watchdog_active(struct watchdog_device *wdd)
--
1.7.11.3
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