From ad532cdbaa71419cb800e42a862287784d80ed75 Mon Sep 17 00:00:00 2001
From: Ivan Poddubny <ivan.poddubny@gmail.com>
Date: Thu, 20 Jul 2006 17:55:40 +0000
Subject: [PATCH] Updated scheduler - now change_task and irq0 handler don't
 intersect so ugly. The code became more straightforward. By the way, it is
 also faster.

git-svn-id: svn://kolibrios.org@101 a494cfbc-eb01-0410-851d-a64ba20cac60
---
 kernel/trunk/core/sched.inc | 159 ++++++++++++++++++++----------------
 1 file changed, 90 insertions(+), 69 deletions(-)

diff --git a/kernel/trunk/core/sched.inc b/kernel/trunk/core/sched.inc
index 048918cd11..4ff0046830 100644
--- a/kernel/trunk/core/sched.inc
+++ b/kernel/trunk/core/sched.inc
@@ -2,6 +2,7 @@
 ;; IRQ0 HANDLER (TIMER INTERRUPT) ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+
 align 32
 irq0:
         save_ring3_context
@@ -9,11 +10,6 @@ irq0:
 	mov   ds, ax
 	mov   es, ax
 
-        mov   edi,[0x3000]
-        shl   edi, 3
-                         ; fields of TSS descriptor:
-;        mov   [edi+gdts+ tss0 +5], word 01010000b *256 +11101001b
-
         inc   dword [timer_ticks]
 
         mov   eax, [timer_ticks]
@@ -26,21 +22,90 @@ irq0:
         call  updatecputimes
      .nocounter:
 
-        mov   edi, [0x3010]
+        cmp   [0xffff], byte 1
+        jne   .change_task
 
+        mov   al,0x20   ; send End Of Interrupt signal
+        mov   dx,0x20
+        out   dx,al
+
+        mov   [0xffff], byte 0
+
+        restore_ring3_context
+        iret
+
+     .change_task:
+        call  update_counters
+
+        call  find_next_task
+        mov   ecx, eax
+
+        mov   al,0x20   ; send End Of Interrupt signal
+        mov   dx,0x20
+        out   dx,al
+
+	test  ecx, ecx  ; if there is only one running process
+        jnz   .return
+
+        call  do_change_task
+        
+     .return:
+        restore_ring3_context
+        iret
+
+
+align 4
+change_task:
+
+        pushfd
+        cli
+        pushad
+
+        call  update_counters
+        call  find_next_task
+        test  eax, eax    ; the same task -> skip switch
+        jnz    .return
+
+        mov   [0xffff],byte 1
+        call  do_change_task
+
+     .return:
+        popad
+        popfd
+
+        ret
+
+
+uglobal
+   align 4
+   far_jump:
+    .offs dd ?
+    .sel  dw ?
+   context_counter     dd ? ;noname & halyavin
+   next_usage_update   dd ?
+   timer_ticks         dd ?
+   prev_slot           dd ?
+   event_sched         dd ?
+endg
+
+
+update_counters:
+        mov   edi, [0x3010]
         mov   ebx, [edi+0x18] ; time stamp counter add
         call  _rdtsc
         sub   eax, ebx
         add   eax, [edi+0x14] ; counter sum
         mov   [edi+0x14], eax
+ret
 
+
+; Find next task to execute
+; result: ebx = number of the selected task
+;         [0xffff] = 1  if the task is the same
+find_next_task:
         mov   ebx,[0x3000]
         mov   [prev_slot], ebx
 
-        cmp   [0xffff], byte 1
-        je    .do_not_change_task
-
-
       .waiting_for_termination:
       .waiting_for_reuse:
       .waiting_for_event:
@@ -55,6 +120,8 @@ irq0:
         inc   ebx
 
         mov   al, byte [edi+0xA]
+        test  al, al
+        jz    .found
 	cmp   al, 1
 	jz    .suspended
 	cmp   al, 2
@@ -77,73 +144,27 @@ irq0:
         mov   [event_sched], eax
         mov   [edi+0xA], byte 0
       .noevents:
-        cmp   ebx, [prev_slot]
-        sete  [0xffff]
-
-
-     .do_not_change_task:
-
+      .found:
+        mov   [0x3000],ebx
+        mov   [0x3010],edi
         call  _rdtsc
         mov   [edi+0x18],eax
 
+	xor   eax, eax
+        cmp   ebx, [prev_slot]
+        sete  al
+ret
+
+; in: ebx = TSS selector index
+do_change_task:
         shl   ebx, 3
         xor   eax, eax
         add   ebx, tss0
-        mov   word  [far_jump.sel],  bx   ; selector
-        mov   dword [far_jump.offs], eax  ; offset
-        
-        cmp   [irq0needeoi],byte 0
-        mov   [irq0needeoi],byte 1          
-        jz    .noeoi
-
-        mov   al,0x20   ; send End Of Interrupt signal
-        mov   dx,0x20
-        out   dx,al
-.noeoi:   
-
-        cmp   [0xffff],byte 0
-        je    .switch
-        dec   byte [0xffff]
-        jz    @f
-     .switch:
+        mov   [far_jump.sel],  bx   ; selector
+        mov   [far_jump.offs], eax  ; offset
         jmp   pword [far_jump]
         inc   [context_counter] ;noname & halyavin
-       @@:
-        
-        restore_ring3_context
-        iret
-
-
-uglobal
-   align 4
-   far_jump:
-    .offs dd ?
-    .sel  dw ?
-   context_counter     dd ? ;noname & halyavin
-   next_usage_update   dd ?
-   timer_ticks         dd ?
-   prev_slot dd ?
-   event_sched dd ?
-endg
-iglobal
-   irq0needeoi         db 1   
-endg
-
-
-align 4
-change_task:
-
-        pushfd
-        cli
-        mov   [0xffff],byte 2
-
-        mov   [irq0needeoi],byte 0
-        dec   dword [timer_ticks]  ; because irq0 will increase it
-
-        int   0x20   ; irq0 handler
-        popfd
-
-        ret
+ret