@@ -50,6 +50,10 @@ extern int register_restart_handler(struct notifier_block *);
extern int unregister_restart_handler(struct notifier_block *);
extern void do_kernel_restart(char *cmd);
+extern int register_pre_restart_handler(struct notifier_block *);
+extern int unregister_pre_restart_handler(struct notifier_block *);
+extern void do_kernel_pre_restart(char *cmd);
+
/*
* Architecture-specific implementations of sys_reboot commands.
*/
@@ -235,6 +235,57 @@ void do_kernel_restart(char *cmd)
atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
}
+/*
+ * Notifier list for kernel code which wants to be called immediately
+ * before restarting the system.
+ */
+static ATOMIC_NOTIFIER_HEAD(pre_restart_handler_list);
+
+/**
+ * register_pre_restart_handler - Register function to be called in preparation
+ * to reset the system
+ * @nb: Info about handler function to be called
+ *
+ * Registers a function with code to be called in preparation to restart
+ * the system.
+ *
+ * Currently always returns zero, as atomic_notifier_chain_register()
+ * always returns zero.
+ */
+int register_pre_restart_handler(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_register(&pre_restart_handler_list, nb);
+}
+EXPORT_SYMBOL(register_pre_restart_handler);
+
+/**
+ * unregister_pre_restart_handler - Unregister previously registered
+ * pre-restart handler
+ * @nb: Hook to be unregistered
+ *
+ * Unregisters a previously registered pre-restart handler function.
+ *
+ * Returns zero on success, or %-ENOENT on failure.
+ */
+int unregister_pre_restart_handler(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_unregister(&pre_restart_handler_list, nb);
+}
+EXPORT_SYMBOL(unregister_pre_restart_handler);
+
+/**
+ * do_kernel_pre_restart - Execute kernel pre-restart handler call chain
+ *
+ * Calls functions registered with register_pre_restart_handler.
+ *
+ * Expected to be called from machine_restart and
+ * machine_emergency_restart before invoking the restart handlers.
+ */
+void do_kernel_pre_restart(char *cmd)
+{
+ atomic_notifier_call_chain(&pre_restart_handler_list, reboot_mode, cmd);
+}
+
void migrate_to_reboot_cpu(void)
{
/* The boot cpu is always logical cpu 0 */
Introduce a new pre_restart notifier chain for callbacks that need to be executed after the system has been made quiescent with syscore_shutdown(), before machine restart. This pre_restart notifier chain should be invoked on machine restart and on emergency machine restart. The use-case for this new notifier chain is to preserve tracing data within pmem areas on systems where the BIOS does not clear memory across warm reboots. Why do we need a new notifier chain ? 1) The reboot and restart_prepare notifiers are called too early in the reboot sequence: they are invoked before syscore_shutdown(), which leaves other CPUs actively running threads while those notifiers are invoked. 2) The "restart" notifier is meant to trigger the actual machine restart, and is not meant to be invoked as a last step immediately before restart. It is also not always used: some architecture code choose to bypass this restart notifier and reboot directly from the architecture code. Wiring up the architecture code to call this notifier chain is left to follow-up arch-specific patches. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: nvdimm@lists.linux.dev Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: x86@kernel.org Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: linux-arm-kernel@lists.infradead.org --- include/linux/reboot.h | 4 ++++ kernel/reboot.c | 51 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 55 insertions(+)