Add a governor which calls a notifier call chain. This allows the
registration of custom functions to the watchdog pretimeout. This is
useful when writing out-of-tree kernel modules and it is more similar to
the register_reboot_notifier or register_oom_notifier API.
Signed-off-by: Stefan Eichenberger <eichest@xxxxxxxxx>
---
drivers/watchdog/Kconfig | 16 ++++++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/pretimeout_notifier.c | 73 ++++++++++++++++++++++++++
drivers/watchdog/watchdog_pretimeout.h | 2 +
include/linux/watchdog.h | 5 ++
5 files changed, 97 insertions(+)
create mode 100644 drivers/watchdog/pretimeout_notifier.c
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 355100dad60a..ec019120effc 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -105,6 +105,14 @@ config WATCHDOG_PRETIMEOUT_GOV_PANIC
Panic watchdog pretimeout governor, on watchdog pretimeout
event put the kernel into panic.
+config WATCHDOG_PRETIMEOUT_GOV_NOTIFIER
+ tristate "Notifier watchdog pretimeout governor"
+ depends on WATCHDOG_CORE
+ default WATCHDOG_CORE
+ help
+ Notifier watchdog pretimeout governor, on watchdog pretimeout
+ event call a notifier call chain.
+
choice
prompt "Default Watchdog Pretimeout Governor"
default WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC
@@ -129,6 +137,14 @@ config WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC
a watchdog pretimeout event happens, consider that
a watchdog feeder is dead and reboot is unavoidable.
+config WATCHDOG_PRETIMEOUT_DEFAULT_GOV_NOTIFIER
+ bool "notifier"
+ depends on WATCHDOG_PRETIMEOUT_GOV_NOTIFIER
+ help
+ Use notifier watchdog pretimeout governor by default,
+ if a watchdog pretiemout event happens, a notifier
+ call chain is called.
+
endchoice
endif # WATCHDOG_PRETIMEOUT_GOV
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index a7eade8b4d45..cb63f4eb89bf 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -12,6 +12,7 @@ watchdog-$(CONFIG_WATCHDOG_PRETIMEOUT_GOV) += watchdog_pretimeout.o
obj-$(CONFIG_WATCHDOG_PRETIMEOUT_GOV_NOOP) += pretimeout_noop.o
obj-$(CONFIG_WATCHDOG_PRETIMEOUT_GOV_PANIC) += pretimeout_panic.o
+obj-$(CONFIG_WATCHDOG_PRETIMEOUT_GOV_NOTIFIER) += pretimeout_notifier.o
# Only one watchdog can succeed. We probe the ISA/PCI/USB based
# watchdog-cards first, then the architecture specific watchdog
diff --git a/drivers/watchdog/pretimeout_notifier.c b/drivers/watchdog/pretimeout_notifier.c
new file mode 100644
index 000000000000..3f845c77ec44
--- /dev/null
+++ b/drivers/watchdog/pretimeout_notifier.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2021 Stefan Eichenberger <eichest@xxxxxxxxx>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/watchdog.h>
+
+#include "watchdog_pretimeout.h"
+
+BLOCKING_NOTIFIER_HEAD(watchdog_pretimeout_notifier_list);
+
+/**
+ * register_watchdog_pretimeout_notifier - Register function to be called on pretimeout
+ * @nb: Info about notifier function to be called
+ *
+ * Registers a function with the list of functions to be called when a watchdog pretimeout occurs.
+ *
+ * Currently always returns zero, as blocking_notifier_chain_register()
+ * always returns zero.
+ */
+int register_watchdog_pretimeout_notifier(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_register(&watchdog_pretimeout_notifier_list, nb);
+}
+EXPORT_SYMBOL(register_watchdog_pretimeout_notifier);
+
+/**
+ * unregister_watchdog_pretimeout_notifier - Unregister previously registered pretimeout notifier
+ * @nb: Hook to be unregistered
+ *
+ * Unregisters a previously registered watchdog pretimeout notifier function.
+ *
+ * Returns zero on success, or %-ENOENT on failure.
+ */
+int unregister_watchdog_pretimeout_notifier(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_unregister(&watchdog_pretimeout_notifier_list, nb);
+}
+EXPORT_SYMBOL(unregister_watchdog_pretimeout_notifier);
+
+/**
+ * pretimeout_notifier - Notify registred methods on pretimeout
+ * @wdd - watchdog_device
+ *
+ * Notify, watchdog has not been fed till pretimeout event.
+ */
+static void pretimeout_notifier(struct watchdog_device *wdd)
+{
+ blocking_notifier_call_chain(&watchdog_pretimeout_notifier_list, 0, wdd);
+}
+
+static struct watchdog_governor watchdog_gov_notifier = {
+ .name = "notifier",
+ .pretimeout = pretimeout_notifier,
+};
+
+static int __init watchdog_gov_notifier_register(void)
+{
+ return watchdog_register_governor(&watchdog_gov_notifier);
+}
+
+static void __exit watchdog_gov_notifier_unregister(void)
+{
+ watchdog_unregister_governor(&watchdog_gov_notifier);
+}
+module_init(watchdog_gov_notifier_register);
+module_exit(watchdog_gov_notifier_unregister);
+
+MODULE_AUTHOR("Stefan Eichenberger <eichest@xxxxxxxxx>");
+MODULE_DESCRIPTION("Notifier watchdog pretimeout governor");
+MODULE_LICENSE("GPL");
diff --git a/drivers/watchdog/watchdog_pretimeout.h b/drivers/watchdog/watchdog_pretimeout.h
index a3f1abc68839..bb00ca1fcadd 100644
--- a/drivers/watchdog/watchdog_pretimeout.h
+++ b/drivers/watchdog/watchdog_pretimeout.h
@@ -28,6 +28,8 @@ int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,
#define WATCHDOG_PRETIMEOUT_DEFAULT_GOV "noop"
#elif IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC)
#define WATCHDOG_PRETIMEOUT_DEFAULT_GOV "panic"
+#elif IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_NOTIFIER)
+#define WATCHDOG_PRETIMEOUT_DEFAULT_GOV "notifier"
#endif
#else
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 9b19e6bb68b5..760beab1007f 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -215,4 +215,9 @@ int watchdog_set_last_hw_keepalive(struct watchdog_device *, unsigned int);
/* devres register variant */
int devm_watchdog_register_device(struct device *dev, struct watchdog_device *);
+#if IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV_NOTIFIER)
+int register_watchdog_pretimeout_notifier(struct notifier_block *nb);
+int unregister_watchdog_pretimeout_notifier(struct notifier_block *nb);
+#endif
+
#endif /* ifndef _LINUX_WATCHDOG_H */
--
2.27.0
