The change converts watchdog device attribute "pretimeout_governor" from
read-only to read-write type to allow users to select a desirable
watchdog pretimeout governor in runtime, e.g.
% echo -n panic > /sys/..../watchdog/watchdog0/pretimeout
To get this working a list of registered pretimeout governors is created
and a new helper function watchdog_pretimeout_governor_set() is exported
to watchdog_dev.c.
If a selected governor is gone, a watchdog device pretimeout notification
is delegated to a default built-in pretimeout governor.
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx>
---
Changes from v3 to v4:
* new change, this functional change was removed in v3
Changes from v2 1/4 to v4:
* introduced watchdog_pretimeout_governor_set() and moved device
attribute registration to watchdog_dev.c
* fixed a list element deregistration bug
drivers/watchdog/watchdog_dev.c | 15 ++++++-
drivers/watchdog/watchdog_pretimeout.c | 76 ++++++++++++++++++++++++++++++++++
drivers/watchdog/watchdog_pretimeout.h | 8 ++++
3 files changed, 98 insertions(+), 1 deletion(-)
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 3837269562a2..af5791d49b73 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -497,7 +497,20 @@ static ssize_t pretimeout_governor_show(struct device *dev,
return watchdog_pretimeout_governor_get(wdd, buf);
}
-static DEVICE_ATTR_RO(pretimeout_governor);
+
+static ssize_t pretimeout_governor_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct watchdog_device *wdd = dev_get_drvdata(dev);
+ int ret = watchdog_pretimeout_governor_set(wdd, buf);
+
+ if (!ret)
+ ret = count;
+
+ return ret;
+}
+static DEVICE_ATTR_RW(pretimeout_governor);
static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
int n)
diff --git a/drivers/watchdog/watchdog_pretimeout.c b/drivers/watchdog/watchdog_pretimeout.c
index 098c965f6c78..d60a5d5b3cd1 100644
--- a/drivers/watchdog/watchdog_pretimeout.c
+++ b/drivers/watchdog/watchdog_pretimeout.c
@@ -29,6 +29,29 @@ struct watchdog_pretimeout {
struct list_head entry;
};
+/* The mutex protects governor list and serializes external interfaces */
+static DEFINE_MUTEX(governor_lock);
+
+/* List of the registered watchdog pretimeout governors */
+static LIST_HEAD(governor_list);
+
+struct governor_priv {
+ struct watchdog_governor *gov;
+ struct list_head entry;
+};
+
+static struct governor_priv *find_governor_by_name(const char *gov_name)
+{
+ struct governor_priv *priv;
+
+ list_for_each_entry(priv, &governor_list, entry)
+ if (!strncmp(gov_name, priv->gov->name,
+ WATCHDOG_GOV_NAME_MAXLEN))
+ return priv;
+
+ return NULL;
+}
+
int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf)
{
int count = 0;
@@ -41,6 +64,28 @@ int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf)
return count;
}
+int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,
+ const char *buf)
+{
+ struct governor_priv *priv;
+
+ mutex_lock(&governor_lock);
+
+ priv = find_governor_by_name(buf);
+ if (!priv) {
+ mutex_unlock(&governor_lock);
+ return -EINVAL;
+ }
+
+ spin_lock_irq(&pretimeout_lock);
+ wdd->gov = priv->gov;
+ spin_unlock_irq(&pretimeout_lock);
+
+ mutex_unlock(&governor_lock);
+
+ return 0;
+}
+
void watchdog_notify_pretimeout(struct watchdog_device *wdd)
{
unsigned long flags;
@@ -59,6 +104,22 @@ EXPORT_SYMBOL_GPL(watchdog_notify_pretimeout);
int watchdog_register_governor(struct watchdog_governor *gov)
{
struct watchdog_pretimeout *p;
+ struct governor_priv *priv;
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ mutex_lock(&governor_lock);
+
+ if (find_governor_by_name(gov->name)) {
+ mutex_unlock(&governor_lock);
+ kfree(priv);
+ return -EBUSY;
+ }
+
+ priv->gov = gov;
+ list_add(&priv->entry, &governor_list);
if (!strncmp(gov->name, WATCHDOG_PRETIMEOUT_DEFAULT_GOV,
WATCHDOG_GOV_NAME_MAXLEN)) {
@@ -71,6 +132,8 @@ int watchdog_register_governor(struct watchdog_governor *gov)
spin_unlock_irq(&pretimeout_lock);
}
+ mutex_unlock(&governor_lock);
+
return 0;
}
EXPORT_SYMBOL(watchdog_register_governor);
@@ -78,12 +141,25 @@ EXPORT_SYMBOL(watchdog_register_governor);
void watchdog_unregister_governor(struct watchdog_governor *gov)
{
struct watchdog_pretimeout *p;
+ struct governor_priv *priv, *t;
+
+ mutex_lock(&governor_lock);
+
+ list_for_each_entry_safe(priv, t, &governor_list, entry) {
+ if (priv->gov == gov) {
+ list_del(&priv->entry);
+ kfree(priv);
+ break;
+ }
+ }
spin_lock_irq(&pretimeout_lock);
list_for_each_entry(p, &pretimeout_list, entry)
if (p->wdd->gov == gov)
p->wdd->gov = default_gov;
spin_unlock_irq(&pretimeout_lock);
+
+ mutex_unlock(&governor_lock);
}
EXPORT_SYMBOL(watchdog_unregister_governor);
diff --git a/drivers/watchdog/watchdog_pretimeout.h b/drivers/watchdog/watchdog_pretimeout.h
index 8f9804c2dd88..afb868eedc65 100644
--- a/drivers/watchdog/watchdog_pretimeout.h
+++ b/drivers/watchdog/watchdog_pretimeout.h
@@ -19,6 +19,8 @@ void watchdog_unregister_governor(struct watchdog_governor *gov);
int watchdog_register_pretimeout(struct watchdog_device *wdd);
void watchdog_unregister_pretimeout(struct watchdog_device *wdd);
int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf);
+int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,
+ const char *buf);
#if IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC)
#define WATCHDOG_PRETIMEOUT_DEFAULT_GOV "panic"
@@ -41,6 +43,12 @@ static inline int watchdog_pretimeout_governor_get(struct watchdog_device *wdd,
{
return -EINVAL;
}
+
+static inline int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,
+ const char *buf)
+{
+ return -EINVAL;
+}
#endif
#endif
--
2.8.1
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