[PATCH v2] watchdog: Start watchdog in watchdog_set_last_hw_keepalive only if appropriate

From: Jan Kiszka <jan.kiszka@web.de>
To: Guenter Roeck <linux@roeck-us.net>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	linux-watchdog@vger.kernel.org
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH v2] watchdog: Start watchdog in watchdog_set_last_hw_keepalive only if appropriate
Date: Sun, 1 Aug 2021 09:56:25 +0200	[thread overview]
Message-ID: <93d56386-6e37-060b-55ce-84de8cde535f@web.de> (raw)

From: Jan Kiszka <jan.kiszka@siemens.com>

We must not pet a running watchdog when handle_boot_enabled is off
because this will kick off automatic triggering before userland is
running, defeating the purpose of the handle_boot_enabled control.
Furthermore, don't ping in case watchdog_set_last_hw_keepalive was
called incorrectly when the hardware watchdog is actually not running.

Fixed: cef9572e9af3 ("watchdog: add support for adjusting last known HW keepalive time")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

Changes to v1 ("watchdog: Respect handle_boot_enabled when setting last last_hw_keepalive"):
 - add watchdog_hw_running test
 - improve commit log

 drivers/watchdog/watchdog_dev.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 3bab32485273..6c73160386b9 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -1172,7 +1172,10 @@ int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,

 	wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));

-	return __watchdog_ping(wdd);
+	if (watchdog_hw_running(wdd) && handle_boot_enabled)
+		return __watchdog_ping(wdd);
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);

--
2.31.1
