Re: [PATCHv3] watchdog: Add stop_on_reboot parameter to control reboot policy

From: Guenter Roeck
Date: Sun Feb 23 2020 - 09:09:35 EST

On 2/23/20 3:49 AM, Dmitry Safonov wrote:
Many watchdog drivers use watchdog_stop_on_reboot() helper in order
to stop the watchdog on system reboot. Unfortunately, this logic is
coded in driver's probe function and doesn't allows user to decide what
to do during shutdown/reboot.

On the other side, Xen and Qemu watchdog drivers (xen_wdt and i6300esb)
may be configured to either send NMI or turn off/reboot VM as
the watchdog action. As the kernel may stuck at any state, sending NMIs
can't reliably reboot the VM.

At Arista, we benefited from the following set-up: the emulated watchdogs
trigger VM reset and softdog is set to catch less severe conditions to
generate vmcore. Just before reboot watchdog's timeout is increased
to some good-enough value (3 mins). That keeps watchdog always running
and guarantees that VM doesn't stuck.

Provide new stop_on_reboot module parameter to let user control
watchdog's reboot policy.

Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
Cc: linux-watchdog@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

v3: Make module parameter read-only in runtime (Thanks Guenter for
spotting the typo!)
v2: Add module parameter instead of ioctl()

drivers/watchdog/watchdog_core.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 861daf4f37b2..423844757812 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -39,6 +39,10 @@
static DEFINE_IDA(watchdog_ida);
+static int stop_on_reboot = -1;
+module_param(stop_on_reboot, int, 0444);
+MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)");
* Deferred Registration infrastructure.
@@ -254,6 +258,14 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
+ /* Module parameter to force watchdog policy on reboot. */
+ if (stop_on_reboot != -1) {
+ if (stop_on_reboot)
+ set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
+ else
+ clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
+ }
if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;