diff options
| -rw-r--r-- | Documentation/watchdog/watchdog-kernel-api.txt | 7 | ||||
| -rw-r--r-- | drivers/watchdog/watchdog_core.c | 118 | ||||
| -rw-r--r-- | include/linux/watchdog.h | 3 |
3 files changed, 110 insertions, 18 deletions
diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt index a0438f3957ca..d8b0d3367706 100644 --- a/Documentation/watchdog/watchdog-kernel-api.txt +++ b/Documentation/watchdog/watchdog-kernel-api.txt @@ -36,6 +36,10 @@ The watchdog_unregister_device routine deregisters a registered watchdog timer device. The parameter of this routine is the pointer to the registered watchdog_device structure. +The watchdog subsystem includes an registration deferral mechanism, +which allows you to register an watchdog as early as you wish during +the boot process. + The watchdog device structure looks like this: struct watchdog_device { @@ -52,6 +56,7 @@ struct watchdog_device { void *driver_data; struct mutex lock; unsigned long status; + struct list_head deferred; }; It contains following fields: @@ -80,6 +85,8 @@ It contains following fields: information about the status of the device (Like: is the watchdog timer running/active, is the nowayout bit set, is the device opened via the /dev/watchdog interface or not, ...). +* deferred: entry in wtd_deferred_reg_list which is used to + register early initialized watchdogs. The list of watchdog operations is defined as: diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c index cec9b559647d..1a8059455413 100644 --- a/drivers/watchdog/watchdog_core.c +++ b/drivers/watchdog/watchdog_core.c @@ -43,6 +43,45 @@ static DEFINE_IDA(watchdog_ida); static struct class *watchdog_class; +/* + * Deferred Registration infrastructure. + * + * Sometimes watchdog drivers needs to be loaded as soon as possible, + * for example when it's impossible to disable it. To do so, + * raising the initcall level of the watchdog driver is a solution. + * But in such case, the miscdev is maybe not ready (subsys_initcall), and + * watchdog_core need miscdev to register the watchdog as a char device. + * + * The deferred registration infrastructure offer a way for the watchdog + * subsystem to register a watchdog properly, even before miscdev is ready. + */ + +static DEFINE_MUTEX(wtd_deferred_reg_mutex); +static LIST_HEAD(wtd_deferred_reg_list); +static bool wtd_deferred_reg_done; + +static int watchdog_deferred_registration_add(struct watchdog_device *wdd) +{ + list_add_tail(&wdd->deferred, + &wtd_deferred_reg_list); + return 0; +} + +static void watchdog_deferred_registration_del(struct watchdog_device *wdd) +{ + struct list_head *p, *n; + struct watchdog_device *wdd_tmp; + + list_for_each_safe(p, n, &wtd_deferred_reg_list) { + wdd_tmp = list_entry(p, struct watchdog_device, + deferred); + if (wdd_tmp == wdd) { + list_del(&wdd_tmp->deferred); + break; + } + } +} + static void watchdog_check_min_max_timeout(struct watchdog_device *wdd) { /* @@ -98,17 +137,7 @@ int watchdog_init_timeout(struct watchdog_device *wdd, } EXPORT_SYMBOL_GPL(watchdog_init_timeout); -/** - * watchdog_register_device() - register a watchdog device - * @wdd: watchdog device - * - * Register a watchdog device with the kernel so that the - * watchdog timer can be accessed from userspace. - * - * A zero is returned on success and a negative errno code for - * failure. - */ -int watchdog_register_device(struct watchdog_device *wdd) +static int __watchdog_register_device(struct watchdog_device *wdd) { int ret, id, devno; @@ -164,16 +193,33 @@ int watchdog_register_device(struct watchdog_device *wdd) return 0; } -EXPORT_SYMBOL_GPL(watchdog_register_device); /** - * watchdog_unregister_device() - unregister a watchdog device - * @wdd: watchdog device to unregister + * watchdog_register_device() - register a watchdog device + * @wdd: watchdog device * - * Unregister a watchdog device that was previously successfully - * registered with watchdog_register_device(). + * Register a watchdog device with the kernel so that the + * watchdog timer can be accessed from userspace. + * + * A zero is returned on success and a negative errno code for + * failure. */ -void watchdog_unregister_device(struct watchdog_device *wdd) + +int watchdog_register_device(struct watchdog_device *wdd) +{ + int ret; + + mutex_lock(&wtd_deferred_reg_mutex); + if (wtd_deferred_reg_done) + ret = __watchdog_register_device(wdd); + else + ret = watchdog_deferred_registration_add(wdd); + mutex_unlock(&wtd_deferred_reg_mutex); + return ret; +} +EXPORT_SYMBOL_GPL(watchdog_register_device); + +static void __watchdog_unregister_device(struct watchdog_device *wdd) { int ret; int devno; @@ -189,8 +235,43 @@ void watchdog_unregister_device(struct watchdog_device *wdd) ida_simple_remove(&watchdog_ida, wdd->id); wdd->dev = NULL; } + +/** + * watchdog_unregister_device() - unregister a watchdog device + * @wdd: watchdog device to unregister + * + * Unregister a watchdog device that was previously successfully + * registered with watchdog_register_device(). + */ + +void watchdog_unregister_device(struct watchdog_device *wdd) +{ + mutex_lock(&wtd_deferred_reg_mutex); + if (wtd_deferred_reg_done) + __watchdog_unregister_device(wdd); + else + watchdog_deferred_registration_del(wdd); + mutex_unlock(&wtd_deferred_reg_mutex); +} + EXPORT_SYMBOL_GPL(watchdog_unregister_device); +static int __init watchdog_deferred_registration(void) +{ + mutex_lock(&wtd_deferred_reg_mutex); + wtd_deferred_reg_done = true; + while (!list_empty(&wtd_deferred_reg_list)) { + struct watchdog_device *wdd; + + wdd = list_first_entry(&wtd_deferred_reg_list, + struct watchdog_device, deferred); + list_del(&wdd->deferred); + __watchdog_register_device(wdd); + } + mutex_unlock(&wtd_deferred_reg_mutex); + return 0; +} + static int __init watchdog_init(void) { int err; @@ -207,6 +288,7 @@ static int __init watchdog_init(void) return err; } + watchdog_deferred_registration(); return 0; } @@ -217,7 +299,7 @@ static void __exit watchdog_exit(void) ida_destroy(&watchdog_ida); } -subsys_initcall(watchdog_init); +subsys_initcall_sync(watchdog_init); module_exit(watchdog_exit); MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h index a746bf5216f8..f47feada5b42 100644 --- a/include/linux/watchdog.h +++ b/include/linux/watchdog.h @@ -65,6 +65,8 @@ struct watchdog_ops { * @driver-data:Pointer to the drivers private data. * @lock: Lock for watchdog core internal use only. * @status: Field that contains the devices internal status bits. + * @deferred: entry in wtd_deferred_reg_list which is used to + * register early initialized watchdogs. * * The watchdog_device structure contains all information about a * watchdog timer device. @@ -95,6 +97,7 @@ 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 */ + struct list_head deferred; }; #define WATCHDOG_NOWAYOUT IS_BUILTIN(CONFIG_WATCHDOG_NOWAYOUT) |