#include <linux/errno.h> /* For the -ENODEV/... values */
#include <linux/fs.h> /* For file operations */
#include <linux/init.h> /* For __init/__exit/... */
+#include <linux/jiffies.h> /* For timeout functions */
#include <linux/kernel.h> /* For printk/panic/... */
#include <linux/kref.h> /* For data references */
#include <linux/miscdevice.h> /* For handling misc devices */
#include <linux/slab.h> /* For memory functions */
#include <linux/types.h> /* For standard types (like size_t) */
#include <linux/watchdog.h> /* For watchdog specific items */
+#include <linux/workqueue.h> /* For workqueue */
#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
#include "watchdog_core.h"
struct cdev cdev;
struct watchdog_device *wdd;
struct mutex lock;
+ unsigned long last_keepalive;
+ unsigned long last_hw_keepalive;
+ struct delayed_work work;
unsigned long status; /* Internal status bits */
#define _WDOG_DEV_OPEN 0 /* Opened ? */
#define _WDOG_ALLOW_RELEASE 1 /* Did we receive the magic char ? */
/* Reference to watchdog device behind /dev/watchdog */
static struct watchdog_core_data *old_wd_data;
+static struct workqueue_struct *watchdog_wq;
+
+static inline bool watchdog_need_worker(struct watchdog_device *wdd)
+{
+ /* All variables in milli-seconds */
+ unsigned int hm = wdd->max_hw_heartbeat_ms;
+ unsigned int t = wdd->timeout * 1000;
+
+ /*
+ * A worker to generate heartbeat requests is needed if all of the
+ * following conditions are true.
+ * - Userspace activated the watchdog.
+ * - The driver provided a value for the maximum hardware timeout, and
+ * thus is aware that the framework supports generating heartbeat
+ * requests.
+ * - Userspace requests a longer timeout than the hardware can handle.
+ */
+ return hm && ((watchdog_active(wdd) && t > hm) ||
+ (t && !watchdog_active(wdd) && watchdog_hw_running(wdd)));
+}
+
+static long watchdog_next_keepalive(struct watchdog_device *wdd)
+{
+ struct watchdog_core_data *wd_data = wdd->wd_data;
+ unsigned int timeout_ms = wdd->timeout * 1000;
+ unsigned long keepalive_interval;
+ unsigned long last_heartbeat;
+ unsigned long virt_timeout;
+ unsigned int hw_heartbeat_ms;
+
+ virt_timeout = wd_data->last_keepalive + msecs_to_jiffies(timeout_ms);
+ hw_heartbeat_ms = min(timeout_ms, wdd->max_hw_heartbeat_ms);
+ keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2);
+
+ if (!watchdog_active(wdd))
+ return keepalive_interval;
+
+ /*
+ * To ensure that the watchdog times out wdd->timeout seconds
+ * after the most recent ping from userspace, the last
+ * worker ping has to come in hw_heartbeat_ms before this timeout.
+ */
+ last_heartbeat = virt_timeout - msecs_to_jiffies(hw_heartbeat_ms);
+ return min_t(long, last_heartbeat - jiffies, keepalive_interval);
+}
+
+static inline void watchdog_update_worker(struct watchdog_device *wdd)
+{
+ struct watchdog_core_data *wd_data = wdd->wd_data;
+
+ if (watchdog_need_worker(wdd)) {
+ long t = watchdog_next_keepalive(wdd);
+
+ if (t > 0)
+ mod_delayed_work(watchdog_wq, &wd_data->work, t);
+ } else {
+ cancel_delayed_work(&wd_data->work);
+ }
+}
+
+static int __watchdog_ping(struct watchdog_device *wdd)
+{
+ struct watchdog_core_data *wd_data = wdd->wd_data;
+ unsigned long earliest_keepalive = wd_data->last_hw_keepalive +
+ msecs_to_jiffies(wdd->min_hw_heartbeat_ms);
+ int err;
+
+ if (time_is_after_jiffies(earliest_keepalive)) {
+ mod_delayed_work(watchdog_wq, &wd_data->work,
+ earliest_keepalive - jiffies);
+ return 0;
+ }
+
+ wd_data->last_hw_keepalive = jiffies;
+
+ if (wdd->ops->ping)
+ err = wdd->ops->ping(wdd); /* ping the watchdog */
+ else
+ err = wdd->ops->start(wdd); /* restart watchdog */
+
+ watchdog_update_worker(wdd);
+
+ return err;
+}
+
/*
* watchdog_ping: ping the watchdog.
* @wdd: the watchdog device to ping
static int watchdog_ping(struct watchdog_device *wdd)
{
- int err;
+ struct watchdog_core_data *wd_data = wdd->wd_data;
- if (!watchdog_active(wdd))
+ if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
return 0;
- if (wdd->ops->ping)
- err = wdd->ops->ping(wdd); /* ping the watchdog */
- else
- err = wdd->ops->start(wdd); /* restart watchdog */
+ wd_data->last_keepalive = jiffies;
+ return __watchdog_ping(wdd);
+}
- return err;
+static void watchdog_ping_work(struct work_struct *work)
+{
+ struct watchdog_core_data *wd_data;
+ struct watchdog_device *wdd;
+
+ wd_data = container_of(to_delayed_work(work), struct watchdog_core_data,
+ work);
+
+ mutex_lock(&wd_data->lock);
+ wdd = wd_data->wdd;
+ if (wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd)))
+ __watchdog_ping(wdd);
+ mutex_unlock(&wd_data->lock);
}
/*
static int watchdog_start(struct watchdog_device *wdd)
{
+ struct watchdog_core_data *wd_data = wdd->wd_data;
+ unsigned long started_at;
int err;
if (watchdog_active(wdd))
return 0;
- err = wdd->ops->start(wdd);
- if (err == 0)
+ started_at = jiffies;
+ if (watchdog_hw_running(wdd) && wdd->ops->ping)
+ err = wdd->ops->ping(wdd);
+ else
+ err = wdd->ops->start(wdd);
+ if (err == 0) {
set_bit(WDOG_ACTIVE, &wdd->status);
+ wd_data->last_keepalive = started_at;
+ watchdog_update_worker(wdd);
+ }
return err;
}
static int watchdog_stop(struct watchdog_device *wdd)
{
- int err;
+ int err = 0;
if (!watchdog_active(wdd))
return 0;
return -EBUSY;
}
- err = wdd->ops->stop(wdd);
- if (err == 0)
+ if (wdd->ops->stop)
+ err = wdd->ops->stop(wdd);
+ else
+ set_bit(WDOG_HW_RUNNING, &wdd->status);
+
+ if (err == 0) {
clear_bit(WDOG_ACTIVE, &wdd->status);
+ watchdog_update_worker(wdd);
+ }
return err;
}
static int watchdog_set_timeout(struct watchdog_device *wdd,
unsigned int timeout)
{
- if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT))
+ int err = 0;
+
+ if (!(wdd->info->options & WDIOF_SETTIMEOUT))
return -EOPNOTSUPP;
if (watchdog_timeout_invalid(wdd, timeout))
return -EINVAL;
- return wdd->ops->set_timeout(wdd, timeout);
+ if (wdd->ops->set_timeout)
+ err = wdd->ops->set_timeout(wdd, timeout);
+ else
+ wdd->timeout = timeout;
+
+ watchdog_update_worker(wdd);
+
+ return err;
}
/*
* If the /dev/watchdog device is open, we don't want the module
* to be unloaded.
*/
- if (!try_module_get(wdd->ops->owner)) {
+ if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) {
err = -EBUSY;
goto out_clear;
}
file->private_data = wd_data;
- kref_get(&wd_data->kref);
+ if (!watchdog_hw_running(wdd))
+ kref_get(&wd_data->kref);
/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
return nonseekable_open(inode, file);
struct watchdog_core_data *wd_data = file->private_data;
struct watchdog_device *wdd;
int err = -EBUSY;
+ bool running;
mutex_lock(&wd_data->lock);
watchdog_ping(wdd);
}
+ cancel_delayed_work_sync(&wd_data->work);
+ watchdog_update_worker(wdd);
+
/* make sure that /dev/watchdog can be re-opened */
clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
done:
+ running = wdd && watchdog_hw_running(wdd);
mutex_unlock(&wd_data->lock);
- /* Allow the owner module to be unloaded again */
- module_put(wd_data->cdev.owner);
- kref_put(&wd_data->kref, watchdog_core_data_release);
+ /*
+ * Allow the owner module to be unloaded again unless the watchdog
+ * is still running. If the watchdog is still running, it can not
+ * be stopped, and its driver must not be unloaded.
+ */
+ if (!running) {
+ module_put(wd_data->cdev.owner);
+ kref_put(&wd_data->kref, watchdog_core_data_release);
+ }
return 0;
}
wd_data->wdd = wdd;
wdd->wd_data = wd_data;
+ if (!watchdog_wq)
+ return -ENODEV;
+
+ INIT_DELAYED_WORK(&wd_data->work, watchdog_ping_work);
+
if (wdd->id == 0) {
old_wd_data = wd_data;
watchdog_miscdev.parent = wdd->parent;
old_wd_data = NULL;
kref_put(&wd_data->kref, watchdog_core_data_release);
}
+ return err;
}
- return err;
+
+ /* Record time of most recent heartbeat as 'just before now'. */
+ wd_data->last_hw_keepalive = jiffies - 1;
+
+ /*
+ * If the watchdog is running, prevent its driver from being unloaded,
+ * 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);
+ }
+
+ return 0;
}
/*
wdd->wd_data = NULL;
mutex_unlock(&wd_data->lock);
+ cancel_delayed_work_sync(&wd_data->work);
+
kref_put(&wd_data->kref, watchdog_core_data_release);
}
{
int err;
+ watchdog_wq = alloc_workqueue("watchdogd",
+ WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
+ if (!watchdog_wq) {
+ pr_err("Failed to create watchdog workqueue\n");
+ return -ENOMEM;
+ }
+
err = class_register(&watchdog_class);
if (err < 0) {
pr_err("couldn't register class\n");
{
unregister_chrdev_region(watchdog_devt, MAX_DOGS);
class_unregister(&watchdog_class);
+ destroy_workqueue(watchdog_wq);
}
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