From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3ytSxJ2P3dzDsPC for ; Fri, 8 Dec 2017 21:18:42 +1100 (AEDT) From: Christophe Leroy Subject: [PATCH v2] watchdog: core: make sure the watchdog worker always works To: Wim Van Sebroeck , Guenter Roeck Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-watchdog@vger.kernel.org Message-Id: <20171208101835.EEB866BA61@localhost.localdomain> Date: Fri, 8 Dec 2017 11:18:35 +0100 (CET) List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , When running a command like 'chrt -f 50 dd if=/dev/zero of=/dev/null', the watchdog_worker fails to service the HW watchdog and the HW watchdog fires long before the watchdog soft timeout. At the moment, the watchdog_worker is invoked as a delayed work. Delayed works are handled by non realtime kernel threads. The WQ_HIGHPRI flag only increases the niceness of that threads. This patch replaces the delayed work logic by kthread delayed work, and sets the associated kernel task to SCHED_FIFO with the highest priority, in order to ensure that the watchdog worker will run as soon as possible. Signed-off-by: Christophe Leroy --- v2: Use kthread_delayed_work instead of hrtimer drivers/watchdog/watchdog_dev.c | 48 +++++++++++++++++++++++------------------ 1 file changed, 27 insertions(+), 21 deletions(-) diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index 1e971a50d7fb..3dcb86f18055 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -39,6 +39,7 @@ #include /* For timeout functions */ #include /* For printk/panic/... */ #include /* For data references */ +#include /* For kthread_delayed_work */ #include /* For handling misc devices */ #include /* For module stuff/... */ #include /* For mutexes */ @@ -46,9 +47,10 @@ #include /* For memory functions */ #include /* For standard types (like size_t) */ #include /* For watchdog specific items */ -#include /* For workqueue */ #include /* For copy_to_user/put_user/... */ +#include /* For struct sched_param */ + #include "watchdog_core.h" #include "watchdog_pretimeout.h" @@ -67,7 +69,7 @@ struct watchdog_core_data { struct mutex lock; unsigned long last_keepalive; unsigned long last_hw_keepalive; - struct delayed_work work; + struct kthread_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 ? */ @@ -79,7 +81,7 @@ static dev_t watchdog_devt; /* Reference to watchdog device behind /dev/watchdog */ static struct watchdog_core_data *old_wd_data; -static struct workqueue_struct *watchdog_wq; +static struct kthread_worker *watchdog_kworker; static bool handle_boot_enabled = IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED); @@ -140,9 +142,10 @@ static inline void watchdog_update_worker(struct watchdog_device *wdd) long t = watchdog_next_keepalive(wdd); if (t > 0) - mod_delayed_work(watchdog_wq, &wd_data->work, t); + kthread_mod_delayed_work(watchdog_kworker, + &wd_data->work, t); } else { - cancel_delayed_work(&wd_data->work); + kthread_cancel_delayed_work_sync(&wd_data->work); } } @@ -154,8 +157,8 @@ static int __watchdog_ping(struct watchdog_device *wdd) int err; if (time_is_after_jiffies(earliest_keepalive)) { - mod_delayed_work(watchdog_wq, &wd_data->work, - earliest_keepalive - jiffies); + kthread_mod_delayed_work(watchdog_kworker, &wd_data->work, + earliest_keepalive - jiffies); return 0; } @@ -203,12 +206,13 @@ static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data) return wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd)); } -static void watchdog_ping_work(struct work_struct *work) +static void watchdog_ping_work(struct kthread_work *work) { struct watchdog_core_data *wd_data; - wd_data = container_of(to_delayed_work(work), struct watchdog_core_data, - work); + wd_data = container_of(container_of(work, struct kthread_delayed_work, + work), + struct watchdog_core_data, work); mutex_lock(&wd_data->lock); if (watchdog_worker_should_ping(wd_data)) @@ -919,10 +923,10 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) wd_data->wdd = wdd; wdd->wd_data = wd_data; - if (!watchdog_wq) + if (IS_ERR_OR_NULL(watchdog_kworker)) return -ENODEV; - INIT_DELAYED_WORK(&wd_data->work, watchdog_ping_work); + kthread_init_delayed_work(&wd_data->work, watchdog_ping_work); if (wdd->id == 0) { old_wd_data = wd_data; @@ -968,7 +972,8 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) if (handle_boot_enabled) { __module_get(wdd->ops->owner); kref_get(&wd_data->kref); - queue_delayed_work(watchdog_wq, &wd_data->work, 0); + kthread_queue_delayed_work(watchdog_kworker, + &wd_data->work, 0); } else { pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n", wdd->id); @@ -1006,7 +1011,7 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) watchdog_stop(wdd); } - cancel_delayed_work_sync(&wd_data->work); + kthread_cancel_delayed_work_sync(&wd_data->work); kref_put(&wd_data->kref, watchdog_core_data_release); } @@ -1110,13 +1115,14 @@ void watchdog_dev_unregister(struct watchdog_device *wdd) int __init watchdog_dev_init(void) { int err; + struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,}; - watchdog_wq = alloc_workqueue("watchdogd", - WQ_HIGHPRI | WQ_MEM_RECLAIM, 0); - if (!watchdog_wq) { - pr_err("Failed to create watchdog workqueue\n"); - return -ENOMEM; + watchdog_kworker = kthread_create_worker(0, "watchdogd"); + if (IS_ERR(watchdog_kworker)) { + pr_err("Failed to create watchdog kworker\n"); + return PTR_ERR(watchdog_kworker); } + sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, ¶m); err = class_register(&watchdog_class); if (err < 0) { @@ -1135,7 +1141,7 @@ int __init watchdog_dev_init(void) err_alloc: class_unregister(&watchdog_class); err_register: - destroy_workqueue(watchdog_wq); + kthread_destroy_worker(watchdog_kworker); return err; } @@ -1149,7 +1155,7 @@ void __exit watchdog_dev_exit(void) { unregister_chrdev_region(watchdog_devt, MAX_DOGS); class_unregister(&watchdog_class); - destroy_workqueue(watchdog_wq); + kthread_destroy_worker(watchdog_kworker); } module_param(handle_boot_enabled, bool, 0444); -- 2.13.3