From 53f96cee1aff74c8ee3c5f7a25df0c01d7117eeb Mon Sep 17 00:00:00 2001 From: Vladimir Zapolskiy Date: Fri, 7 Oct 2016 15:37:00 +0300 Subject: watchdog: pretimeout: add option to select a pretimeout governor in runtime 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 Reviewed-by: Guenter Roeck Reviewed-by: Wolfram Sang Tested-by: Wolfram Sang Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck --- drivers/watchdog/watchdog_pretimeout.c | 76 ++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) (limited to 'drivers/watchdog/watchdog_pretimeout.c') diff --git a/drivers/watchdog/watchdog_pretimeout.c b/drivers/watchdog/watchdog_pretimeout.c index 098c965f6c78..c9e4a0326938 100644 --- a/drivers/watchdog/watchdog_pretimeout.c +++ b/drivers/watchdog/watchdog_pretimeout.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include "watchdog_pretimeout.h" @@ -29,6 +30,28 @@ 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 (sysfs_streq(gov_name, priv->gov->name)) + 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); -- cgit v1.2.3-59-g8ed1b