From 4a90de95215e57f13bd0631f7d60e66dce2afc09 Mon Sep 17 00:00:00 2001
From: xamidev <xamidev@riseup.net>
Date: Sun, 1 Feb 2026 11:25:43 +0100
Subject: [PATCH] 10ms Round Robin scheduler (blank processes)

---
 src/idt/idt.c         |  7 ++++++-
 src/kernel.h          |  3 +++
 src/kmain.c           | 27 +++++++++++++++------------
 src/sched/process.c   |  2 +-
 src/sched/scheduler.c | 28 +++++++++++++++++++++++++++-
 src/sched/scheduler.h |  1 +
 src/string/string.c   | 13 +++++++++++++
 src/string/string.h   |  1 +
 8 files changed, 67 insertions(+), 15 deletions(-)

diff --git a/src/idt/idt.c b/src/idt/idt.c
index 434fb63..f6665bf 100644
--- a/src/idt/idt.c
+++ b/src/idt/idt.c
@@ -188,7 +188,12 @@ struct cpu_status_t* interrupt_dispatch(struct cpu_status_t* context)
         case 32:
             //DEBUG("Timer Interrupt");
             ticks++;
-            scheduler_schedule();
+            if (ticks % SCHEDULER_QUANTUM == 0)
+            {
+                CLEAR_INTERRUPTS;
+                scheduler_schedule();
+                SET_INTERRUPTS;
+            }
             // Send an EOI so that we can continue having interrupts
             outb(0x20, 0x20);
             break;
diff --git a/src/kernel.h b/src/kernel.h
index a4a2736..1ce75d6 100644
--- a/src/kernel.h
+++ b/src/kernel.h
@@ -36,4 +36,7 @@ struct boot_context
 	struct limine_kernel_address_response* kaddr;
 };
 
+// 1 tick = 1 ms => quantum = 10ms
+#define SCHEDULER_QUANTUM 10
+
 #endif
diff --git a/src/kmain.c b/src/kmain.c
index a30cbfe..4874f7f 100644
--- a/src/kmain.c
+++ b/src/kmain.c
@@ -15,6 +15,7 @@
 #include "mem/paging/vmm.h"
 #include "mem/heap/kheap.h"
 #include "sched/process.h"
+#include "sched/scheduler.h"
 
 // Limine version used
 __attribute__((used, section(".limine_requests")))
@@ -57,6 +58,7 @@ static volatile LIMINE_REQUESTS_END_MARKER;
 // Panic (should dump registers etc. in the future)
 void hcf()
 {
+	//CLEAR_INTERRUPTS;
 	for (;;)
 	{
 		asm("hlt");
@@ -101,7 +103,6 @@ void kmain()
 	gdt_init();
 	idt_init();
 	timer_init();
-	SET_INTERRUPTS;
 
 	pmm_init(boot_ctx.mmap, boot_ctx.hhdm);
 
@@ -116,21 +117,23 @@ void kmain()
 	void* ptr3 = kmalloc(5); DEBUG("(KMALLOC TEST) Allocated 5 bytes at 0x%p", ptr3);
 
 	vmm_init();
+	
+	struct process_t* pedicel = process_create();
+	struct process_t* two = process_create();
+	struct process_t* three = process_create();
+
+	process_add(&processes_list, pedicel);
+	process_add(&processes_list, two);
+	process_add(&processes_list, three);
+	process_display_list(processes_list);
+
+	scheduler_init();
+
+	SET_INTERRUPTS;
 
 	keyboard_init(FR);
-
 	term_init();
 	kputs(splash);
 
-	for (int i=0; i<10; i++)
-	{
-		printf("testing, attention please %d\n", i);
-	}
-	
-	struct process_t* pedicel = process_create();
-
-	process_add(&processes_list, pedicel);
-	process_display_list(processes_list);
-
 	hcf();
 }
diff --git a/src/sched/process.c b/src/sched/process.c
index 3ce3654..574de44 100644
--- a/src/sched/process.c
+++ b/src/sched/process.c
@@ -19,7 +19,7 @@ void process_display_list(struct process_t* processes_list)
     struct process_t* tmp = processes_list;
     while (tmp != NULL)
     {
-        DEBUG("{%d: } -> ", process_view_id);
+        DEBUG("{%d: %p} -> ", process_view_id, tmp);
         tmp = tmp->next;
         process_view_id++;
     }
diff --git a/src/sched/scheduler.c b/src/sched/scheduler.c
index 1ac1ed5..6bf3a39 100644
--- a/src/sched/scheduler.c
+++ b/src/sched/scheduler.c
@@ -1,9 +1,35 @@
 #include "kernel.h"
+#include "process.h"
 
 extern struct process_t* processes_list;
 extern struct process_t* current_process;
 
+// DEBUG: how many times we did schedule
+int scheduled = 0;
+
+void scheduler_init()
+{
+    // Choose first process?
+    current_process = processes_list;
+}
+
 void scheduler_schedule()
 {
-    DEBUG("Scheduler called!");
+    //DEBUG("Scheduler called!");
+    if (current_process->next != NULL)
+    {
+        current_process = current_process->next;
+    } else
+    {
+        current_process = processes_list;
+    }
+    scheduled++;
+    DEBUG("SCHEDULER CALLED: current_process=%p", current_process);
+
+    // debug
+    /* if (scheduled == 5)
+    {
+        DEBUG("enough, halting");
+        hcf();
+    } */
 }
\ No newline at end of file
diff --git a/src/sched/scheduler.h b/src/sched/scheduler.h
index daf425e..6da8442 100644
--- a/src/sched/scheduler.h
+++ b/src/sched/scheduler.h
@@ -2,5 +2,6 @@
 #define SCHEDULER_H
 
 void scheduler_schedule();
+void scheduler_init();
 
 #endif
\ No newline at end of file
diff --git a/src/string/string.c b/src/string/string.c
index 1992eee..0d63d14 100644
--- a/src/string/string.c
+++ b/src/string/string.c
@@ -1,6 +1,19 @@
+#include <stddef.h>
+
 char* strcpy(char *dest, const char *src)
 {
     char *temp = dest;
     while((*dest++ = *src++));
     return temp;
+}
+
+// https://stackoverflow.com/questions/2488563/strcat-implementation
+char *strcat(char *dest, const char *src){
+    size_t i,j;
+    for (i = 0; dest[i] != '\0'; i++)
+        ;
+    for (j = 0; src[j] != '\0'; j++)
+        dest[i+j] = src[j];
+    dest[i+j] = '\0';
+    return dest;
 }
\ No newline at end of file
diff --git a/src/string/string.h b/src/string/string.h
index 49a8ea0..1c0306e 100644
--- a/src/string/string.h
+++ b/src/string/string.h
@@ -2,5 +2,6 @@
 #define STRING_H
 
 char *strcpy(char *dest, const char *src);
+char *strcat(char *dest, const char *src);
 
 #endif
\ No newline at end of file