If the watchdog timeout is set such that the crash kernel does not
have time to collect a coredump and the crash kernel is not equipped to
ping the watchdog timer itself, then a kernel coredump will not be collected
before the watchdog fires. This change registers a panic notifier and
callback so the watchdog timeout can be extended if a kernel panic occurs.
This timeout extension would give the crash kernel enough time to collect
a coredump before the CPU resets. The watchdog timeout is extended if and only
if a crash kernel image is loaded in memory, the watchdog is active at the
time of the panic, and the kconfig setting is set.
A Kconfig option has been added to configure the timeout duration at
compile-time. Default is zero seconds.
Signed-off-by: JP Ertola <jp.ertola@xxxxxxx>
---
v4: Remove optional callback mechanism alltogether. I agree with Guenter,
not widely used.
v3: Fix logic so timeout extension is not longer than wdd->max_timeout
v2: Remove dead code and comments.
drivers/watchdog/Kconfig | 13 ++++++
drivers/watchdog/watchdog_dev.c | 80 ++++++++++++++++++++++++++++++++-
include/linux/watchdog.h | 1 +
3 files changed, 93 insertions(+), 1 deletion(-)
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index fd7968635e6d..f1055985e100 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -141,6 +141,19 @@ comment "Watchdog Device Drivers"
# Architecture Independent
+config DEFAULT_WATCHDOG_CRASH_KERNEL_TIMEOUT
+ int "Default timeout for watchdog timer before crash kernel starts (seconds)"
+ default 0
+ help
+ This option allows an extended timeout to be used for the watchdog when
+ the kernel panics and a crash kernel is about to start. This is helpful
+ when the existing WDT timeout value is less than the time required for
+ crash kernel to run and the crash kernel is unable to handle the
+ the watchdog itself. The timeout extension happens last in chain of
+ kernel panic handler callbacks just in case another panic handler
+ hangs unexpectedly. When this value is set to 0, the watchdog timeout
+ will not be changed.
+
config SOFT_WATCHDOG
tristate "Software watchdog"
select WATCHDOG_CORE
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 2946f3a63110..cf91c08b0606 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -34,6 +34,7 @@
#include <linux/init.h> /* For __init/__exit/... */
#include <linux/hrtimer.h> /* For hrtimers */
#include <linux/kernel.h> /* For printk/panic/... */
+#include <linux/kexec.h> /* For checking if crash kernel is loaded */
#include <linux/kthread.h> /* For kthread_work */
#include <linux/miscdevice.h> /* For handling misc devices */
#include <linux/module.h> /* For module stuff/... */
@@ -82,6 +83,8 @@ static bool handle_boot_enabled =
static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
+static unsigned int wdt_panic_timeout = CONFIG_DEFAULT_WATCHDOG_CRASH_KERNEL_TIMEOUT;
+
static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
{
return ktime_after(ktime_get(), data->open_deadline);
@@ -658,6 +661,59 @@ static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
* off the watchdog (if 'nowayout' is not set).
*/
+static int watchdog_panic_notifier(struct notifier_block *nb,
+ unsigned long code, void *data)
+{
+ struct watchdog_device *wdd;
+ int ret = 0;
+ unsigned int time_out = wdt_panic_timeout;
+
+ if (wdt_panic_timeout == 0)
+ return NOTIFY_DONE;
+
+ wdd = container_of(nb, struct watchdog_device, panic_nb);
+
+ if (watchdog_timeout_invalid(wdd, wdt_panic_timeout)) {
+ time_out = min(wdt_panic_timeout, wdd->max_timeout);
+ pr_err("watchdog%d: timeout extension value "
+ " invalid. Falling back to %d seconds\n", wdd->id,
+ time_out);
+ }
+
+ if (kexec_crash_image && watchdog_active(wdd)) {
+ int ping_ret = 0;
+
+ pr_info("watchdog%d: Extending watchdog timeout to "
+ "%d seconds\n", wdd->id, time_out);
+
+ ret = watchdog_set_timeout(wdd, time_out);
+
+ if (ret) {
+ pr_err("watchdog%d: Unable to extend watchdog timeout "
+ "before starting crash kernel (%d)",
+ wdd->id, ret);
+ }
+
+ /* Many watchdog implementations will reset the timer
+ * when the timeout is changed, but ping again to be
+ * safe.
+ */
+ if (wdd->ops->ping) {
+ ping_ret = wdd->ops->ping(wdd);
+ if (ping_ret) {
+ pr_warn("watchdog%d: Unable to ping "
+ "watchdog before starting "
+ "crash kernel (%d)\n",
+ wdd->id, ping_ret);
+ }
+ }
+
+
+ }
+
+ return notifier_from_errno(ret);
+}
+
static ssize_t watchdog_write(struct file *file, const char __user *data,
size_t len, loff_t *ppos)
{
@@ -1118,8 +1174,25 @@ int watchdog_dev_register(struct watchdog_device *wdd)
return ret;
ret = watchdog_register_pretimeout(wdd);
- if (ret)
+ if (ret) {
watchdog_cdev_unregister(wdd);
+ return ret;
+ }
+
+ /*
+ * Setting panic_nb priority to minimum ensures the watchdog device
+ * panic callback runs last in the chain of kernel panic callbacks.
+ * This way, the watchdog device will still fire in the event another
+ * panic callback hangs.
+ */
+ wdd->panic_nb.priority = INT_MIN;
+ wdd->panic_nb.notifier_call = watchdog_panic_notifier;
+
+ ret = atomic_notifier_chain_register(&panic_notifier_list,
+ &wdd->panic_nb);
+ if (ret)
+ pr_err("watchdog%d: Cannot register panic notifier (%d)\n",
+ wdd->id, ret);
return ret;
}
@@ -1228,3 +1301,8 @@ module_param(open_timeout, uint, 0644);
MODULE_PARM_DESC(open_timeout,
"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");
+
+module_param(wdt_panic_timeout, uint, 0444);
+MODULE_PARM_DESC(wdt_panic_timeout,
+ "Watchdog timeout extension duration upon kernel panic. (default="
+ __MODULE_STRING(CONFIG_DEFAULT_WATCHDOG_CRASH_KERNEL_TIMEOUT) " seconds)");
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 9b19e6bb68b5..bc7e6e8aa7ab 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -107,6 +107,7 @@ struct watchdog_device {
unsigned int max_hw_heartbeat_ms;
struct notifier_block reboot_nb;
struct notifier_block restart_nb;
+ struct notifier_block panic_nb;
void *driver_data;
struct watchdog_core_data *wd_data;
unsigned long status;
--
2.29.0
