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Subject[PATCH 2/2] watchdog/uapi: Add WDIOS_{RUN,STOP}_ON_REBOOT
Date
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 WDIOS_RUN_ON_REBOOT and WDIOS_STOP_ON_REBOOT ioctl options
to set up strategy on reboot.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
drivers/watchdog/watchdog_dev.c | 12 ++++++++++++
include/linux/watchdog.h | 6 ++++++
include/uapi/linux/watchdog.h | 3 ++-
3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 8b5c742f24e8..c854cd0245db 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -753,6 +753,18 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
}
if (val & WDIOS_ENABLECARD)
err = watchdog_start(wdd);
+
+ if (val & WDIOS_RUN_ON_REBOOT) {
+ if (val & WDIOS_STOP_ON_REBOOT) {
+ err = -EINVAL;
+ break;
+ }
+ watchdog_run_on_reboot(wdd);
+ err = 0;
+ } else if (val & WDIOS_STOP_ON_REBOOT) {
+ watchdog_stop_on_reboot(wdd);
+ err = 0;
+ }
break;
case WDIOC_KEEPALIVE:
if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 417d9f37077a..9e2ca7754631 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -150,6 +150,12 @@ static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd)
set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
}

+/* Use the following function to keep the watchdog running on reboot */
+static inline void watchdog_run_on_reboot(struct watchdog_device *wdd)
+{
+ clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
+}
+
/* Use the following function to stop the watchdog when unregistering it */
static inline void watchdog_stop_on_unregister(struct watchdog_device *wdd)
{
diff --git a/include/uapi/linux/watchdog.h b/include/uapi/linux/watchdog.h
index b15cde5c9054..bf19a5d3c987 100644
--- a/include/uapi/linux/watchdog.h
+++ b/include/uapi/linux/watchdog.h
@@ -53,6 +53,7 @@ struct watchdog_info {
#define WDIOS_DISABLECARD 0x0001 /* Turn off the watchdog timer */
#define WDIOS_ENABLECARD 0x0002 /* Turn on the watchdog timer */
#define WDIOS_TEMPPANIC 0x0004 /* Kernel panic on temperature trip */
-
+#define WDIOS_RUN_ON_REBOOT 0x0008 /* Keep watchdog enabled on reboot */
+#define WDIOS_STOP_ON_REBOOT 0x0010 /* Turn off the watchdog on reboot */

#endif /* _UAPI_LINUX_WATCHDOG_H */
--
2.25.0
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