i86/mtx-16-bit/mtx/samples/LAB2/t.c

   1 /************ t.c file **********************************/
   2 #define NPROC     9
   3 #define SSIZE  1024                /* kstack int size */
   4
   5 #define DEAD      0                /* proc status     */
   6 #define READY     1
   7
   8 typedef struct proc{
   9     struct proc *next;
  10            int  ksp;               /* saved sp; offset = 2 */
  11            int  pid;
  12            int  status;            /* READY|DEAD, etc */
  13            int  kstack[SSIZE];     // kmode stack of task
  14 }PROC;
  15
  16 #include "io.c"  /* <===== use YOUR OWN io.c with printf() ****/
  17
  18 PROC proc[NPROC], *running;
  19
  20 int  procSize = sizeof(PROC);
  21
  22 /****************************************************************
  23  Initialize the proc's as shown:
  24         running ---> proc[0] -> proc[1];
  25
  26         proc[1] to proc[N-1] form a circular list:
  27
  28         proc[1] --> proc[2] ... --> proc[NPROC-1] -->
  29           ^                                         |
  30           |<---------------------------------------<-
  31
  32         Each proc's kstack contains:
  33         retPC, ax, bx, cx, dx, bp, si, di, flag;  all 2 bytes
  34 *****************************************************************/
  35
  36 int body();
  37
  38 int initialize()
  39 {
  40   int i, j;
  41   PROC *p;
  42
  43   for (i=0; i < NPROC; i++){
  44     p = &proc[i];
  45     p->next = &proc[i+1];
  46     p->pid = i;
  47     p->status = READY;
  48
  49     if (i){     // initialize kstack[ ] of proc[1] to proc[N-1]
  50       for (j=1; j<10; j++)
  51           p->kstack[SSIZE - j] = 0;          // all saved registers = 0
  52       p->kstack[SSIZE-1]=(int)body;          // called tswitch() from body
  53       p->ksp = &(p->kstack[SSIZE-9]);        // ksp -> kstack top
  54     }
  55   }
  56   running = &proc[0];
  57   proc[NPROC-1].next = &proc[1];
  58   printf("initialization complete\n");
  59 }
  60
  61 char *gasp[NPROC]={
  62      "Oh! You are killing me .......",
  63      "Oh! I am dying ...............",
  64      "Oh! I am a goner .............",
  65      "Bye! Bye! World...............",
  66 };
  67
  68 int grave(){
  69   printf("\n*****************************************\n");
  70   printf("Task %d %s\n", running->pid,gasp[(running->pid) % 4]);
  71   printf("*****************************************\n");
  72   running->status = DEAD;
  73
  74   tswitch();   /* journey of no return */
  75 }
  76
  77 int ps()
  78 {
  79   PROC *p;
  80
  81   printf("running = %d\n", running->pid);
  82
  83   p = running;
  84   p = p->next;
  85   printf("readyProcs = ");
  86   while(p != running && p->status==READY){
  87     printf("%d -> ", p->pid);
  88     p = p->next;
  89   }
  90   printf("\n");
  91 }
  92
  93 int body()
  94 {  char c;
  95    while(1){
  96       ps();
  97       printf("I am Proc %d in body()\n", running->pid);
  98       printf("Input a char : [s|q] ");
  99        c=getc();
 100        switch(c){
 101             case 's': tswitch(); break;
 102             case 'q': grave();   break;
 103             default :            break;
 104        }
 105    }
 106 }
 107
 108
 109 main()
 110 {
 111  printf("\nWelcome to the 460 Multitasking System\n");
 112    initialize();
 113    printf("P0 switch to P1\n");
 114    tswitch();
 115  printf("P0 resumes: all dead, happy ending\n");
 116 }
 117
 118
 119 int scheduler()
 120 {
 121     PROC *p;
 122     p = running->next;
 123
 124     while (p->status != READY && p != running)
 125       p = p->next;
 126
 127     if (p == running)
 128        running = &proc[0];
 129     else
 130        running = p;
 131
 132     printf("\n-----------------------------\n");
 133     printf("next running proc = %d\n", running->pid);
 134     printf("-----------------------------\n");
 135 }