Simple scheduler

src/kernel/boot/kmain.c

@@ -6,6 +6,7 @@
 #include <cpu.h>
 #include <interrupts.h>
 #include <thread.h>
+#include <scheduler.h>
 
 void thread_function()
 {
@@ -36,9 +37,9 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
 
   debug_ok("Boot \"Complete\"\n");
 
-  new_thread(thread_function);
-  new_thread(thread_function);
-  new_thread(thread_function);
+  ready(new_thread(thread_function));
+  ready(new_thread(thread_function));
+  ready(new_thread(thread_function));
   yield();
 
   PANIC("Reached end of kernel main function\n");

src/kernel/include/scheduler.h

@@ -0,0 +1,4 @@
+#pragma once
+
+void ready(struct thread *th);
+struct thread *scheduler_next();

src/kernel/include/thread.h

@@ -7,6 +7,7 @@ struct tcb
   uintptr_t stack_ptr;
   uint64_t tid;
   uint64_t state;
+  struct thread *next;
 };
 
 #define TCB_OFFSET (PAGE_SIZE - sizeof(struct tcb))
@@ -31,12 +32,10 @@ struct thread
   struct tcb tcb;
 };
 
-extern struct thread *threads[];
-int current_tid;
+struct thread *current_thread;
+#define CURRENT_THREAD() (current_thread)
 
-#define CURRENT_THREAD() (threads[current_tid])
-
-struct thread *new_thread(void (*function)());
+struct thread *new_thread(void (*function)(void));
 void yield();
 int get_tid();
 

src/kernel/proc/scheduler.c

@@ -0,0 +1,26 @@
+#include <thread.h>
+
+struct {
+  struct thread *first;
+  struct thread *last;
+} readyQ = {0,0};
+
+void ready(struct thread *th)
+{
+  if(!readyQ.last)
+  {
+    th->tcb.next = 0;
+    readyQ.first = readyQ.last = th;
+  } else {
+    readyQ.last->tcb.next = th;
+    readyQ.last = th;
+  }
+}
+
+struct thread *scheduler_next()
+{
+  struct thread *th = readyQ.first;
+  if(!(readyQ.first = th->tcb.next))
+    readyQ.last = 0;
+  return th;
+}

src/kernel/proc/thread.c

@@ -1,14 +1,13 @@
 #include <thread.h>
-
-struct thread *threads[8];
-int current_tid = -1;
-int tid = 0;
+#include <scheduler.h>
 
 struct thread dummy;
+struct thread *current_thread = 0;
 
-struct thread *new_thread(void (*function)())
+uint64_t tid = 1;
+struct thread *new_thread(void (*function)(void))
 {
-  struct thread *th = threads[tid] = P2V(pmm_alloc());
+  struct thread *th = P2V(pmm_alloc());
 
   th->tcb.tid = tid++;
   th->RBP = (uint64_t)&th->RBP2;
@@ -20,22 +19,20 @@ struct thread *new_thread(void (*function)())
 
 void switch_thread(struct thread *old, struct thread *new)
 {
+  current_thread = new;
   swtch(&old->tcb.stack_ptr, &new->tcb.stack_ptr);
 }
 
 void yield()
 {
   struct thread *old, *new;
-  if(current_tid == -1)
-    old = &dummy;
+
+  old = current_thread;
+  if(old)
+    ready(old);
   else
-    old = threads[current_tid];
-
-  current_tid++;
-  if(current_tid == tid)
-    current_tid = 0;
-
-  new = threads[current_tid];
+    old = &dummy;
+  while(!(new = scheduler_next()));
 
   switch_thread(old, new);
 }