[PATCH v2 1/2] watchdog: introduce watchdog_dev_suspend/resume
From: Grzegorz Jaszczyk
Date: Fri Jun 18 2021 - 15:51:10 EST
The watchdog drivers often disable wdog clock during suspend and then
enable it again during resume. Nevertheless the ping worker is still
running and can issue low-level ping while the wdog clock is disabled
causing the system hang. To prevent such condition register pm notifier
in the watchdog core which will call watchdog_dev_suspend/resume and
actually cancel ping worker during suspend and restore it back, if
needed, during resume.
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx>
---
v1->v2:
- Instead of using watchdog_dev_suspend/resume directly in wdog drivers
suspend/resume callbacks, register pm notifier in the watchdog core when
new WDOG_NO_PING_ON_SUSPEND status flag is set by the driver. Suggested
by Guenter Roeck <linux@xxxxxxxxxxxx>.
- Initialize ret variable in watchdog_dev_suspend/resume.
- Drop EXPORT_SYMBOL_GPL for watchdog_dev_suspend/resume since from now
one they are used only by the watchdog core and not by the drivers.
- Commit log was updated accordingly.
---
drivers/watchdog/watchdog_core.c | 37 +++++++++++++++++++++++++
drivers/watchdog/watchdog_dev.c | 47 ++++++++++++++++++++++++++++++++
include/linux/watchdog.h | 10 +++++++
3 files changed, 94 insertions(+)
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 5df0a22e2cb4..3fe8a7edc252 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -34,6 +34,7 @@
#include <linux/idr.h> /* For ida_* macros */
#include <linux/err.h> /* For IS_ERR macros */
#include <linux/of.h> /* For of_get_timeout_sec */
+#include <linux/suspend.h>
#include "watchdog_core.h" /* For watchdog_dev_register/... */
@@ -185,6 +186,33 @@ static int watchdog_restart_notifier(struct notifier_block *nb,
return NOTIFY_DONE;
}
+static int watchdog_pm_notifier(struct notifier_block *nb, unsigned long mode,
+ void *data)
+{
+ struct watchdog_device *wdd;
+ int ret = 0;
+
+ wdd = container_of(nb, struct watchdog_device, pm_nb);
+
+ switch (mode) {
+ case PM_HIBERNATION_PREPARE:
+ case PM_RESTORE_PREPARE:
+ case PM_SUSPEND_PREPARE:
+ ret = watchdog_dev_suspend(wdd);
+ break;
+ case PM_POST_HIBERNATION:
+ case PM_POST_RESTORE:
+ case PM_POST_SUSPEND:
+ ret = watchdog_dev_resume(wdd);
+ break;
+ }
+
+ if (ret)
+ return NOTIFY_BAD;
+
+ return NOTIFY_DONE;
+}
+
/**
* watchdog_set_restart_priority - Change priority of restart handler
* @wdd: watchdog device
@@ -292,6 +320,15 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
wdd->id, ret);
}
+ if (test_bit(WDOG_NO_PING_ON_SUSPEND, &wdd->status)) {
+ wdd->pm_nb.notifier_call = watchdog_pm_notifier;
+
+ ret = register_pm_notifier(&wdd->pm_nb);
+ if (ret)
+ pr_warn("watchdog%d: Cannot register pm handler (%d)\n",
+ wdd->id, ret);
+ }
+
return 0;
}
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 2946f3a63110..9d1c340a3024 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -1219,6 +1219,53 @@ void __exit watchdog_dev_exit(void)
kthread_destroy_worker(watchdog_kworker);
}
+int watchdog_dev_suspend(struct watchdog_device *wdd)
+{
+ struct watchdog_core_data *wd_data = wdd->wd_data;
+ int ret = 0;
+
+ if (!wdd->wd_data)
+ return -ENODEV;
+
+ /* ping for the last time before suspend */
+ mutex_lock(&wd_data->lock);
+ if (watchdog_worker_should_ping(wd_data))
+ ret = __watchdog_ping(wd_data->wdd);
+ mutex_unlock(&wd_data->lock);
+
+ if (ret)
+ return ret;
+
+ /*
+ * make sure that watchdog worker will not kick in when the wdog is
+ * suspended
+ */
+ hrtimer_cancel(&wd_data->timer);
+ kthread_cancel_work_sync(&wd_data->work);
+
+ return 0;
+}
+
+int watchdog_dev_resume(struct watchdog_device *wdd)
+{
+ struct watchdog_core_data *wd_data = wdd->wd_data;
+ int ret = 0;
+
+ if (!wdd->wd_data)
+ return -ENODEV;
+
+ /*
+ * __watchdog_ping will also retrigger hrtimer and therefore restore the
+ * ping worker if needed.
+ */
+ mutex_lock(&wd_data->lock);
+ if (watchdog_worker_should_ping(wd_data))
+ ret = __watchdog_ping(wd_data->wdd);
+ mutex_unlock(&wd_data->lock);
+
+ return ret;
+}
+
module_param(handle_boot_enabled, bool, 0444);
MODULE_PARM_DESC(handle_boot_enabled,
"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 9b19e6bb68b5..99660197a36c 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -107,6 +107,7 @@ struct watchdog_device {
unsigned int max_hw_heartbeat_ms;
struct notifier_block reboot_nb;
struct notifier_block restart_nb;
+ struct notifier_block pm_nb;
void *driver_data;
struct watchdog_core_data *wd_data;
unsigned long status;
@@ -116,6 +117,7 @@ struct watchdog_device {
#define WDOG_STOP_ON_REBOOT 2 /* Should be stopped on reboot */
#define WDOG_HW_RUNNING 3 /* True if HW watchdog running */
#define WDOG_STOP_ON_UNREGISTER 4 /* Should be stopped on unregister */
+#define WDOG_NO_PING_ON_SUSPEND 5 /* Ping worker should be stopped on suspend */
struct list_head deferred;
};
@@ -156,6 +158,12 @@ static inline void watchdog_stop_on_unregister(struct watchdog_device *wdd)
set_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status);
}
+/* Use the following function to stop the wdog ping worker when suspending */
+static inline void watchdog_stop_ping_on_suspend(struct watchdog_device *wdd)
+{
+ set_bit(WDOG_NO_PING_ON_SUSPEND, &wdd->status);
+}
+
/* Use the following function to check if a timeout value is invalid */
static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigned int t)
{
@@ -209,6 +217,8 @@ extern int watchdog_init_timeout(struct watchdog_device *wdd,
unsigned int timeout_parm, struct device *dev);
extern int watchdog_register_device(struct watchdog_device *);
extern void watchdog_unregister_device(struct watchdog_device *);
+int watchdog_dev_suspend(struct watchdog_device *wdd);
+int watchdog_dev_resume(struct watchdog_device *wdd);
int watchdog_set_last_hw_keepalive(struct watchdog_device *, unsigned int);
--
2.29.0