Task Scheduler

git-svn-id: https://spexeah.com:8443/svn/Asuro@109 6dbc8c32-bb84-406f-8558-d1cf31a0ab0c

src/kernel.pas

@@ -13,7 +13,8 @@ uses
      console,
      bios_data_area,
      keyboard,
-     memorymanager;
+     memorymanager,
+     scheduler;
  
 procedure kmain(mbinfo: Pmultiboot_info_t; mbmagic: uint32); stdcall;
  
@@ -49,8 +50,9 @@ begin
      idt.init();
      isr.init();
      irq.init();
-
      memorymanager.init();
+     scheduler.init();
+
      pint2:= kalloc(18);
      pint:= kalloc(sizeof(uint32));
      if pint = nil then console.writestringln('!');
@@ -59,13 +61,14 @@ begin
      console.writeintln(pint^);
      kfree(pint);
      pint2:= kalloc(128);
-     util.halt_and_catch_fire;
 
      STI;
      isr32.hook(uint32(@bios_data_area.tick_update));
 
      //drivers
      keyboard.init(keyboard_layout);
+     scheduler.add_task(5);
+     scheduler.add_task(15);
 
      asm
         MOV dds, CS

src/scheduler.pas

@@ -0,0 +1,80 @@
+unit scheduler;
+
+interface
+
+uses
+    console,
+    isr32,
+    memorymanager;
+
+const
+    Quantum = 64;
+
+type
+    TScheduler_Entry = packed record
+        ThreadID : uint32;
+        Priority : uint8;
+        Delta    : uint32;
+        Next     : void;
+    end;
+    PScheduler_Entry = ^TScheduler_Entry;
+
+procedure init;
+procedure add_task(priority : uint8);
+
+implementation
+
+var
+   Tick         : uint32;
+   Root_Task    : PScheduler_Entry = nil;
+   Current_Task : PScheduler_Entry = nil;
+
+procedure context_switch();
+begin
+    // This will switch contexts eventually,
+    // For now just print upon context switch.
+    Current_Task:= PScheduler_Entry(Current_Task^.Next);
+    console.writestring('Task: ');
+    console.writeintln(Current_Task^.ThreadID);
+end;
+
+procedure add_task(priority : uint8);
+var
+    new_task : PScheduler_Entry;
+    task     : PScheduler_Entry;
+    i        : uint32;
+
+begin
+    new_task:= PScheduler_Entry(kalloc(sizeof(TScheduler_Entry)));
+    new_task^.Priority:= priority;
+    new_task^.Delta:= Tick;
+    new_task^.Next:= void(Root_Task);
+    task:= Root_Task;
+    i:= 1;
+    while PScheduler_Entry(task^.next) <> Root_Task do begin
+        i:= i+1;
+        task:= PScheduler_Entry(task^.next);
+    end;
+    task^.next:= void(new_task);
+    new_task^.ThreadID:= i;
+end;
+
+procedure delta(data : void);
+begin
+    Tick:= Tick + 1;
+    If (Current_Task^.Delta + (Current_Task^.Priority * Quantum)) <= Tick then context_switch();
+end;
+
+procedure init;
+begin
+    Root_Task:= PScheduler_Entry(kalloc(sizeof(TScheduler_Entry)));
+    Root_Task^.ThreadID:= 0;
+    Root_Task^.Priority:= 1;
+    Root_Task^.Delta:= 0;
+    Root_Task^.Next:= void(Root_Task);
+    Current_Task:= Root_Task;
+    Tick:= 0;
+    isr32.hook(uint32(@delta));
+end;
+
+end.