[PATCH] watchdog: Inform about watchdog timeout.

[Mathieu Othacehe <othacehe@gnu.org>]

When the kernel stops feeding the watchdog, inform the user that it is
about to timeout in X seconds.

The message looks like: watchdog: watchdog0: timeout in 15 seconds

This is helpful to warn the user that, most likely,
CONFIG_WATCHDOG_OPEN_TIMEOUT seconds have elapsed and the userspace hasn't
start feeding the watchdog.

Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>
---
 drivers/watchdog/watchdog_dev.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index e2bd266b1b5b3..0d95c91365993 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -104,6 +104,7 @@ static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
 	ktime_t last_heartbeat, latest_heartbeat;
 	ktime_t virt_timeout;
 	unsigned int hw_heartbeat_ms;
+	int delta_to_timeout;
 
 	if (watchdog_active(wdd))
 		virt_timeout = ktime_add(wd_data->last_keepalive,
@@ -121,6 +122,17 @@ static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
 	 */
 	last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
 	latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
+
+	/*
+	 * If we are past the last heartbeat, inform the user that we are
+	 * about to timeout.
+	 */
+	delta_to_timeout =
+		(int)ktime_ms_delta(virt_timeout, ktime_get()) / MSEC_PER_SEC;
+	if (latest_heartbeat <= 0 && delta_to_timeout > 0)
+		pr_info("watchdog%d: timeout in %d seconds\n", wdd->id,
+			delta_to_timeout);
+
 	if (ktime_before(latest_heartbeat, keepalive_interval))
 		return latest_heartbeat;
 	return keepalive_interval;
-- 
2.45.2