From 4c9f9a68e074395e21fdfe339c1756a0d28dc57c Mon Sep 17 00:00:00 2001
From: "K. Lange" <klange@toaruos.org>
Date: Mon, 22 Jan 2024 07:29:34 +0900
Subject: [PATCH] kernel: Use a common kidle thread that always calls
 switch_next

---
 kernel/arch/x86_64/pit.c |  6 ++----
 kernel/sys/process.c     | 14 ++------------
 2 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/kernel/arch/x86_64/pit.c b/kernel/arch/x86_64/pit.c
index d39bca97..3dcb9d49 100644
--- a/kernel/arch/x86_64/pit.c
+++ b/kernel/arch/x86_64/pit.c
@@ -66,11 +66,9 @@ int pit_interrupt(struct regs *r) {
 
 	irq_ack(0);
 
+	if (r->cs == 0x08) return 1;
+
 	switch_task(1);
-	asm volatile (
-		".global _ret_from_preempt_source\n"
-		"_ret_from_preempt_source:"
-	);
 	return 1;
 }
 
diff --git a/kernel/sys/process.c b/kernel/sys/process.c
index c3e1c442..3e1296b1 100644
--- a/kernel/sys/process.c
+++ b/kernel/sys/process.c
@@ -156,8 +156,6 @@ void switch_next(void) {
 	__builtin_unreachable();
 }
 
-extern void * _ret_from_preempt_source;
-
 /**
  * @brief Yield the processor to the next available task.
  *
@@ -173,7 +171,7 @@ void switch_task(uint8_t reschedule) {
 	/* switch_task() called but the scheduler isn't enabled? Resume... this is probably a bug. */
 	if (!this_core->current_process) return;
 
-	if (this_core->current_process == this_core->kernel_idle_task && __builtin_return_address(0) != &_ret_from_preempt_source) {
+	if (this_core->current_process == this_core->kernel_idle_task) {
 		arch_fatal_prepare();
 		printf("Context switch from kernel_idle_task triggered from somewhere other than pre-emption source. Halting.\n");
 		printf("This generally means that a driver responding to interrupts has attempted to yield in its interrupt context.\n");
@@ -316,15 +314,7 @@ pid_t get_next_pid(void) {
 static void _kidle(void) {
 	while (1) {
 		arch_pause();
-	}
-}
-
-static void _kburn(void) {
-	while (1) {
-		arch_pause();
-#ifndef __aarch64__
 		switch_next();
-#endif
 	}
 }
 
@@ -361,7 +351,7 @@ process_t * spawn_kidle(int bsp) {
 		MMU_FLAG_KERNEL);
 
 	/* TODO arch_initialize_context(uintptr_t) ? */
-	idle->thread.context.ip = bsp ? (uintptr_t)&_kidle : (uintptr_t)&_kburn;
+	idle->thread.context.ip = (uintptr_t)&_kidle;
 	idle->thread.context.sp = idle->image.stack;
 	idle->thread.context.bp = idle->image.stack;