Hi,
Some applications require to start watchdog before userspace software.
This patch enables such feature. Only WATCHDOG_KERNEL_PING flag is
necessary to enable it (attached example for stmp3xxx_rtc_wdt.c).
Moreover kernel's ping is re-enabled when userspace software closed
watchdog using the magic character. The features improves kernel's
reliable if hardware watchdog is available.
* Can you comment the proposed patch?
* Shoud dynamic or static timer_list be used (small structure...)?
* I also added wdd->ops->ref/unref calls but I'm afraid that even
original code is buggy in watchdog_dev.c. Is any driver that uses the
pointers? In my opinion watchdog_open() should call wdd->ops->ref()
before watchdog_start() and watchdog_release() should call
wdd->ops->unref() before module_put(). Otherwise fault is possible if
watchdog module is unloaded.
* I noticed that current watchdog core does not support suspend/resume
case. If you want to use suspend without the patch you need to close a
watchdog in userspace using the magic character before suspend command.
With the patch you must to use WDIOC_SETOPTIONS ioctl and
WDIOS_DISABLECARD/WDIOS_ENABLECARD. Is there any other method to suspend
with watchdog?
best regards
Janusz Uzycki
Signed-off-by: Janusz Uzycki <j.uzycki@xxxxxxxxxxxxxx>
diff --git a/linux-3.14.17/drivers/watchdog/stmp3xxx_rtc_wdt.c b/linux-3.14.17/drivers/watchdog/stmp3xxx_rtc_wdt.c
index b4d6b34..52c5f1c 100644
--- a/linux-3.14.17/drivers/watchdog/stmp3xxx_rtc_wdt.c
+++ b/linux-3.14.17/drivers/watchdog/stmp3xxx_rtc_wdt.c
@@ -78,6 +78,7 @@ static int stmp3xxx_wdt_probe(struct platform_device *pdev)
stmp3xxx_wdd.timeout = clamp_t(unsigned, heartbeat, 1, STMP3XXX_MAX_TIMEOUT);
+ stmp3xxx_wdd.status |= WATCHDOG_KERNEL_PING;
ret = watchdog_register_device(&stmp3xxx_wdd);
if (ret < 0) {
dev_err(&pdev->dev, "cannot register watchdog device\n");
diff --git a/linux-3.14.17/drivers/watchdog/watchdog_dev.c b/linux-3.14.17/drivers/watchdog/watchdog_dev.c
index 6aaefba..d4fae2c 100644
--- a/linux-3.14.17/drivers/watchdog/watchdog_dev.c
+++ b/linux-3.14.17/drivers/watchdog/watchdog_dev.c
@@ -41,6 +41,8 @@
#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/slab.h> /* for kernel ping timer (dynamic) */
+#include <linux/jiffies.h> /* for kernel ping timer */
#include "watchdog_core.h"
@@ -277,6 +279,34 @@ out_ioctl:
return err;
}
+/* kernel ping feature */
+static void watchdog_kping_timer_cb(unsigned long data)
+{
+ struct watchdog_device *wdd = (struct watchdog_device *)data;
+ if (test_bit(WDOG_KERNEL_PING, &wdd->status) && !test_bit(WDOG_DEV_OPEN, &wdd->status)) {
+ watchdog_ping(wdd);
+ /* call next ping a second or 0.5s before hardware timeout */
+ mod_timer(wdd->kping_timer, wdd->timeout > 1 ?
+ jiffies + (wdd->timeout - 1) * HZ : jiffies + HZ/2);
+ }
+}
+
+static void watchdog_kping_start(struct watchdog_device *wdd)
+{
+ if (wdd->ops->ref)
+ wdd->ops->ref(wdd);
+ watchdog_start(wdd);
+ watchdog_ping(wdd);
+ mod_timer(wdd->kping_timer, jiffies + HZ/2);
+}
+
+static void watchdog_kping_stop(struct watchdog_device *wdd)
+{
+ del_timer_sync(wdd->kping_timer);
+ if (wdd->ops->unref)
+ wdd->ops->unref(wdd);
+}
+
/*
* watchdog_write: writes to the watchdog.
* @file: file from VFS
@@ -430,6 +460,9 @@ static int watchdog_open(struct inode *inode, struct file *file)
if (!try_module_get(wdd->ops->owner))
goto out;
+ if (test_bit(WDOG_KERNEL_PING, &wdd->status))
+ watchdog_kping_stop(wdd);
+
err = watchdog_start(wdd);
if (err < 0)
goto out_mod;
@@ -472,8 +505,13 @@ static int watchdog_release(struct inode *inode, struct file *file)
if (!test_bit(WDOG_ACTIVE, &wdd->status))
err = 0;
else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
- !(wdd->info->options & WDIOF_MAGICCLOSE))
- err = watchdog_stop(wdd);
+ !(wdd->info->options & WDIOF_MAGICCLOSE)) {
+ if (test_bit(WDOG_KERNEL_PING, &wdd->status)) {
+ watchdog_kping_start(wdd);
+ err = 0;
+ } else
+ err = watchdog_stop(wdd);
+ }
/* If the watchdog was not stopped, send a keepalive ping */
if (err < 0) {
@@ -524,6 +562,16 @@ int watchdog_dev_register(struct watchdog_device *watchdog)
{
int err, devno;
+ if (test_bit(WDOG_KERNEL_PING, &watchdog->status)) {
+ if (!try_module_get(watchdog->ops->owner))
+ return -ENODEV;
+ watchdog->kping_timer = kzalloc(sizeof(*watchdog->kping_timer), GFP_KERNEL);
+ if (!watchdog->kping_timer)
+ return -ENOMEM;
+ setup_timer(watchdog->kping_timer, watchdog_kping_timer_cb, (unsigned long)watchdog);
+ watchdog_kping_start(watchdog);
+ }
+
if (watchdog->id == 0) {
old_wdd = watchdog;
watchdog_miscdev.parent = watchdog->parent;
@@ -575,6 +623,15 @@ int watchdog_dev_unregister(struct watchdog_device *watchdog)
misc_deregister(&watchdog_miscdev);
old_wdd = NULL;
}
+
+ if (test_bit(WDOG_KERNEL_PING, &watchdog->status) || watchdog->kping_timer) {
+ watchdog_kping_stop(watchdog);
+ watchdog_stop(watchdog);
+ kfree(watchdog->kping_timer);
+ watchdog->kping_timer = NULL;
+ watchdog_stop(watchdog);
+ module_put(watchdog->ops->owner);
+ }
return 0;
}
diff --git a/linux-3.14.17/include/linux/watchdog.h b/linux-3.14.17/include/linux/watchdog.h
index 2a3038e..8cf9148 100644
--- a/linux-3.14.17/include/linux/watchdog.h
+++ b/linux-3.14.17/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 kernel ping timer */
#include <uapi/linux/watchdog.h>
struct watchdog_ops;
@@ -95,6 +96,9 @@ 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_KERNEL_PING 5 /* Ping is done by kernel if device not opened by userland */
+ struct timer_list *kping_timer; /* kernel ping timer */
+#define WATCHDOG_KERNEL_PING (1 << WDOG_KERNEL_PING)
};
#ifdef CONFIG_WATCHDOG_NOWAYOUT
