From 1e464d1d1431d9d715bda598402295a4892ec72a Mon Sep 17 00:00:00 2001
From: "K. Lange" <klange@toaruos.org>
Date: Thu, 27 May 2021 19:41:25 +0900
Subject: [PATCH] Let other APs sleep until there's something to schedule

---
 base/usr/include/kernel/process.h | 1 +
 kernel/arch/x86_64/acpi.c         | 9 +++++++++
 kernel/sys/process.c              | 4 ++++
 3 files changed, 14 insertions(+)

diff --git a/base/usr/include/kernel/process.h b/base/usr/include/kernel/process.h
index 9502622..a7823b2 100644
--- a/base/usr/include/kernel/process.h
+++ b/base/usr/include/kernel/process.h
@@ -216,4 +216,5 @@ extern void arch_set_kernel_stack(uintptr_t);
 extern void arch_enter_user(uintptr_t entrypoint, int argc, char * argv[], char * envp[], uintptr_t stack);
 __attribute__((noreturn))
 extern void arch_enter_signal_handler(uintptr_t,int);
+extern void arch_wakeup_others(void);
 
diff --git a/kernel/arch/x86_64/acpi.c b/kernel/arch/x86_64/acpi.c
index 223d795..fc3643f 100644
--- a/kernel/arch/x86_64/acpi.c
+++ b/kernel/arch/x86_64/acpi.c
@@ -282,3 +282,12 @@ void acpi_initialize(void) {
 	}
 }
 
+void arch_wakeup_others(void) {
+	/* Never wake up BSP, don't hit ourselves, easy. */
+	for (int i = 1; i < processor_count; ++i) {
+		if (i == this_core->cpu_id) continue;
+		if (processor_local_data[i].current_process == processor_local_data[i].kernel_idle_task) {
+			lapic_send_ipi(processor_local_data[i].lapic_id, 0x407E);
+		}
+	}
+}
diff --git a/kernel/sys/process.c b/kernel/sys/process.c
index eec3ce2..cdf4e44 100644
--- a/kernel/sys/process.c
+++ b/kernel/sys/process.c
@@ -293,6 +293,7 @@ static void _kidle(void) {
 
 static void _kburn(void) {
 	while (1) {
+		arch_pause();
 		if (((volatile list_t *)process_queue)->head) switch_next();
 	}
 }
@@ -558,6 +559,8 @@ void make_process_ready(volatile process_t * proc) {
 	spin_lock(process_queue_lock);
 	list_append(process_queue, (node_t*)&proc->sched_node);
 	spin_unlock(process_queue_lock);
+
+	arch_wakeup_others();
 }
 
 /**
@@ -866,6 +869,7 @@ int waitpid(int pid, int * status, int options) {
 			}
 			int pid = candidate->id;
 			if (candidate->flags & PROC_FLAG_FINISHED) {
+				while (*((volatile int *)&candidate->flags) & PROC_FLAG_RUNNING);
 				process_delete((process_t*)candidate);
 			}
 			return pid;