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.
As a preparation to move the watchdog's decision to stop on reboot or
not in userspace, allow WDOG_STOP_ON_REBOOT to be set during runtime,
not only on driver's probing. Always register reboot notifier and check
WDOG_STOP_ON_REBOOT inside it (on actual reboot).
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
---
drivers/watchdog/watchdog_dev.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 4b2a85438478..8766dd93028f 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -1103,6 +1103,10 @@ static int watchdog_reboot_notifier(struct notifier_block *nb,
struct watchdog_device *wdd;
wdd = container_of(nb, struct watchdog_device, reboot_nb);
+
+ if (!test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
+ return NOTIFY_DONE;
+
if (code == SYS_DOWN || code == SYS_HALT) {
if (watchdog_active(wdd)) {
int ret;
@@ -1139,16 +1143,13 @@ int watchdog_dev_register(struct watchdog_device *wdd)
return ret;
}
- if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
- wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
+ wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
- ret = devm_register_reboot_notifier(&wdd->wd_data->dev,
- &wdd->reboot_nb);
- if (ret) {
- pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
- wdd->id, ret);
- watchdog_dev_unregister(wdd);
- }
+ ret = devm_register_reboot_notifier(&wdd->wd_data->dev, &wdd->reboot_nb);
+ if (ret) {
+ pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
+ wdd->id, ret);
+ watchdog_dev_unregister(wdd);
}
return ret;
--
2.25.0
