From ef90174f821041313d42d99c1c8b35a3af64a910 Mon Sep 17 00:00:00 2001 From: Jean-Baptiste Theou Date: Tue, 9 Jun 2015 09:55:02 -0700 Subject: watchdog: watchdog_core: Add watchdog registration deferral mechanism Currently, watchdog subsystem require the misc subsystem to register a watchdog. This may not be the case in case of an early registration of a watchdog, which can be required when the watchdog cannot be disabled. This patch introduces a deferral mechanism to remove this requirement. Signed-off-by: Jean-Baptiste Theou Reviewed-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck --- drivers/watchdog/watchdog_core.c | 118 +++++++++++++++++++++++++++++++++------ 1 file changed, 100 insertions(+), 18 deletions(-) (limited to 'drivers/watchdog/watchdog_core.c') 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 "); -- cgit v1.2.3