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-rw-r--r--Documentation/watchdog/watchdog-parameters.txt8
-rw-r--r--drivers/watchdog/watchdog_dev.c36
2 files changed, 43 insertions, 1 deletions
diff --git a/Documentation/watchdog/watchdog-parameters.txt b/Documentation/watchdog/watchdog-parameters.txt
index 0b88e333f9e1..32d3606caa65 100644
--- a/Documentation/watchdog/watchdog-parameters.txt
+++ b/Documentation/watchdog/watchdog-parameters.txt
@@ -8,6 +8,14 @@ See Documentation/admin-guide/kernel-parameters.rst for information on
providing kernel parameters for builtin drivers versus loadable
modules.
+The watchdog core parameter watchdog.open_timeout is the maximum time,
+in seconds, for which the watchdog framework will take care of pinging
+a running hardware watchdog until userspace opens the corresponding
+/dev/watchdogN device. A value of 0 (the default) means an infinite
+timeout. Setting this to a non-zero value can be useful to ensure that
+either userspace comes up properly, or the board gets reset and allows
+fallback logic in the bootloader to try something else.
+
-------------------------------------------------
acquirewdt:
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 252a7c7b6592..e4b51db48f0e 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -69,6 +69,7 @@ struct watchdog_core_data {
struct mutex lock;
ktime_t last_keepalive;
ktime_t last_hw_keepalive;
+ ktime_t open_deadline;
struct hrtimer timer;
struct kthread_work work;
unsigned long status; /* Internal status bits */
@@ -87,6 +88,19 @@ static struct kthread_worker *watchdog_kworker;
static bool handle_boot_enabled =
IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
+static unsigned open_timeout;
+
+static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
+{
+ return ktime_after(ktime_get(), data->open_deadline);
+}
+
+static void watchdog_set_open_deadline(struct watchdog_core_data *data)
+{
+ data->open_deadline = open_timeout ?
+ ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
+}
+
static inline bool watchdog_need_worker(struct watchdog_device *wdd)
{
/* All variables in milli-seconds */
@@ -211,7 +225,13 @@ static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
{
struct watchdog_device *wdd = wd_data->wdd;
- return wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd));
+ if (!wdd)
+ return false;
+
+ if (watchdog_active(wdd))
+ return true;
+
+ return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
}
static void watchdog_ping_work(struct kthread_work *work)
@@ -824,6 +844,15 @@ static int watchdog_open(struct inode *inode, struct file *file)
if (!hw_running)
kref_get(&wd_data->kref);
+ /*
+ * open_timeout only applies for the first open from
+ * userspace. Set open_deadline to infinity so that the kernel
+ * will take care of an always-running hardware watchdog in
+ * case the device gets magic-closed or WDIOS_DISABLECARD is
+ * applied.
+ */
+ wd_data->open_deadline = KTIME_MAX;
+
/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
return stream_open(inode, file);
@@ -983,6 +1012,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
/* Record time of most recent heartbeat as 'just before now'. */
wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
+ watchdog_set_open_deadline(wd_data);
/*
* If the watchdog is running, prevent its driver from being unloaded,
@@ -1181,3 +1211,7 @@ 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="
__MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
+
+module_param(open_timeout, uint, 0644);
+MODULE_PARM_DESC(open_timeout,
+ "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default=0)");