diff options
| -rw-r--r-- | include/linux/reboot.h | 3 | ||||
| -rw-r--r-- | kernel/reboot.c | 81 |
2 files changed, 84 insertions, 0 deletions
diff --git a/include/linux/reboot.h b/include/linux/reboot.h index 48bf152761c7..67fc8fcdc4b0 100644 --- a/include/linux/reboot.h +++ b/include/linux/reboot.h @@ -38,6 +38,9 @@ extern int reboot_force; extern int register_reboot_notifier(struct notifier_block *); extern int unregister_reboot_notifier(struct notifier_block *); +extern int register_restart_handler(struct notifier_block *); +extern int unregister_restart_handler(struct notifier_block *); +extern void do_kernel_restart(char *cmd); /* * Architecture-specific implementations of sys_reboot commands. diff --git a/kernel/reboot.c b/kernel/reboot.c index a3a9e240fcdb..5925f5ae8dff 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -104,6 +104,87 @@ int unregister_reboot_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(unregister_reboot_notifier); +/* + * Notifier list for kernel code which wants to be called + * to restart the system. + */ +static ATOMIC_NOTIFIER_HEAD(restart_handler_list); + +/** + * register_restart_handler - Register function to be called to reset + * the system + * @nb: Info about handler function to be called + * @nb->priority: Handler priority. Handlers should follow the + * following guidelines for setting priorities. + * 0: Restart handler of last resort, + * with limited restart capabilities + * 128: Default restart handler; use if no other + * restart handler is expected to be available, + * and/or if restart functionality is + * sufficient to restart the entire system + * 255: Highest priority restart handler, will + * preempt all other restart handlers + * + * Registers a function with code to be called to restart the + * system. + * + * Registered functions will be called from machine_restart as last + * step of the restart sequence (if the architecture specific + * machine_restart function calls do_kernel_restart - see below + * for details). + * Registered functions are expected to restart the system immediately. + * If more than one function is registered, the restart handler priority + * selects which function will be called first. + * + * Restart handlers are expected to be registered from non-architecture + * code, typically from drivers. A typical use case would be a system + * where restart functionality is provided through a watchdog. Multiple + * restart handlers may exist; for example, one restart handler might + * restart the entire system, while another only restarts the CPU. + * In such cases, the restart handler which only restarts part of the + * hardware is expected to register with low priority to ensure that + * it only runs if no other means to restart the system is available. + * + * Currently always returns zero, as atomic_notifier_chain_register() + * always returns zero. + */ +int register_restart_handler(struct notifier_block *nb) +{ + return atomic_notifier_chain_register(&restart_handler_list, nb); +} +EXPORT_SYMBOL(register_restart_handler); + +/** + * unregister_restart_handler - Unregister previously registered + * restart handler + * @nb: Hook to be unregistered + * + * Unregisters a previously registered restart handler function. + * + * Returns zero on success, or %-ENOENT on failure. + */ +int unregister_restart_handler(struct notifier_block *nb) +{ + return atomic_notifier_chain_unregister(&restart_handler_list, nb); +} +EXPORT_SYMBOL(unregister_restart_handler); + +/** + * do_kernel_restart - Execute kernel restart handler call chain + * + * Calls functions registered with register_restart_handler. + * + * Expected to be called from machine_restart as last step of the restart + * sequence. + * + * Restarts the system immediately if a restart handler function has been + * registered. Otherwise does nothing. + */ +void do_kernel_restart(char *cmd) +{ + atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd); +} + void migrate_to_reboot_cpu(void) { /* The boot cpu is always logical cpu 0 */ |