text: #include "types.h"
  #include "defs.h"
  #include "param.h"
  #include "mmu.h"
  #include "x86.h"
  #include "proc.h"
  #include "spinlock.h"
  #include "pstat.h"
  #include "rand.h"
  
  struct {
    struct spinlock lock;
    struct proc proc[NPROC];
  } ptable;
  
  static struct proc *initproc;
  
  int nextpid = 1;
  int numberOfTickets = 0;
  
  extern void forkret(void);
  extern void trapret(void);
  
  static void wakeup1(void *chan);
  
  void
  pinit(void)
  {
    initlock(&ptable.lock, "ptable");
  }
  
  // Look in the process table for an UNUSED proc.
  // If found, change state to EMBRYO and initialize
  // state required to run in the kernel.
  // Otherwise return 0.
  static struct proc*
  allocproc(void)
  {
    struct proc *p;
    char *sp;
  
    acquire(&ptable.lock);
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
      if(p->state == UNUSED)
        goto found;
    release(&ptable.lock);
    return 0;
  
  found:
    p->state = EMBRYO;
    p->pid = nextpid++;
    p->numTickets = 1; // assign tickets
    p->numTicks = 0;
    release(&ptable.lock);
  
    // Allocate kernel stack if possible.
    if((p->kstack = kalloc()) == 0){
      p->state = UNUSED;
      return 0;
    }
    sp = p->kstack + KSTACKSIZE;
    
    // Leave room for trap frame.
    sp -= sizeof *p->tf;
    p->tf = (struct trapframe*)sp;
    
    // Set up new context to start executing at forkret,
    // which returns to trapret.
    sp -= 4;
    *(uint*)sp = (uint)trapret;
  
    sp -= sizeof *p->context;
    p->context = (struct context*)sp;
    memset(p->context, 0, sizeof *p->context);
    p->context->eip = (uint)forkret;
  
    return p;
  }
  
  void test(struct pstat *table, struct proc *p){
    table->inuse[0] = 1;
    table->tickets[0] = p->numTickets;
    table->pid[0] = p->pid;
    table->ticks[0] = 0;
  }
  
  // Set up first user process.
  void
  userinit(void)
  {
    struct proc *p;
    extern char _binary_initcode_start[], _binary_initcode_size[];
    
    p = allocproc();
    acquire(&ptable.lock);
    initproc = p;
  
    // Loop through pstat
    // if insue = 0,
    // fill pstat with then fill that slot, break loop
    if((p->pgdir = setupkvm()) == 0)
      panic("userinit: out of memory?");
    inituvm(p->pgdir, _binary_initcode_start, (int)_binary_initcode_size);
    p->sz = PGSIZE;
    memset(p->tf, 0, sizeof(*p->tf));
    p->tf->cs = (SEG_UCODE << 3) | DPL_USER;
    p->tf->ds = (SEG_UDATA << 3) | DPL_USER;
    p->tf->es = p->tf->ds;
    p->tf->ss = p->tf->ds;
    p->tf->eflags = FL_IF;
    p->tf->esp = PGSIZE;
    p->tf->eip = 0;  // beginning of initcode.S
  
    safestrcpy(p->name, "initcode", sizeof(p->name));
    p->cwd = namei("/");
  
    p->state = RUNNABLE;
    release(&ptable.lock);
  }
  
  // Grow current process's memory by n bytes.
  // Return 0 on success, -1 on failure.
  int
  growproc(int n)
  {
    uint sz;
    
    sz = proc->sz;
    if(n > 0){
      if((sz = allocuvm(proc->pgdir, sz, sz + n)) == 0)
        return -1;
    } else if(n < 0){
      if((sz = deallocuvm(proc->pgdir, sz, sz + n)) == 0)
        return -1;
    }
    proc->sz = sz;
    switchuvm(proc);
    return 0;
  }
  
  // Create a new process copying p as the parent.
  // Sets up stack to return as if from system call.
  // Caller must set state of returned proc to RUNNABLE.
  int
  fork(void)
  {
    int i, pid;
    struct proc *np;
    // struct pstat *pstat;
    // Allocate process.
    if((np = allocproc()) == 0)
      return -1;
  
    // Copy process state from p.
    if((np->pgdir = copyuvm(proc->pgdir, proc->sz)) == 0){
      kfree(np->kstack);
      np->kstack = 0;
      np->state = UNUSED;
      return -1;
    }
    np->sz = proc->sz;
    np->parent = proc;
    *np->tf = *proc->tf;
    np->numTickets = proc->numTickets;
  
    // Clear %eax so that fork returns 0 in the child.
    np->tf->eax = 0;
  
    for(i = 0; i < NOFILE; i++)
      if(proc->ofile[i])
        np->ofile[i] = filedup(proc->ofile[i]);
    np->cwd = idup(proc->cwd);
   
    pid = np->pid;
    np->state = RUNNABLE;
    safestrcpy(np->name, proc->name, sizeof(proc->name));
    return pid;
  }
  
  // Exit the current process.  Does not return.
  // An exited process remains in the zombie state
  // until its parent calls wait() to find out it exited.
  void
  exit(void)
  {
    struct proc *p;
    int fd;
  
    if(proc == initproc)
      panic("init exiting");
  
    // Close all open files.
    for(fd = 0; fd < NOFILE; fd++){
      if(proc->ofile[fd]){
        fileclose(proc->ofile[fd]);
        proc->ofile[fd] = 0;
      }
    }
  
    iput(proc->cwd);
    proc->cwd = 0;
  
    acquire(&ptable.lock);
  
    // Parent might be sleeping in wait().
    wakeup1(proc->parent);
  
    // Pass abandoned children to init.
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
      if(p->parent == proc){
        p->parent = initproc;
        if(p->state == ZOMBIE)
          wakeup1(initproc);
      }
    }
  
    // Jump into the scheduler, never to return.
    proc->state = ZOMBIE;
    sched();
    panic("zombie exit");
  }
  
  // Wait for a child process to exit and return its pid.
  // Return -1 if this process has no children.
  int
  wait(void)
  {
    struct proc *p;
    int havekids, pid;
  
    acquire(&ptable.lock);
    for(;;){
      // Scan through table looking for zombie children.
      havekids = 0;
      for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
        if(p->parent != proc)
          continue;
        havekids = 1;
        if(p->state == ZOMBIE){
          // Found one.
          pid = p->pid;
          kfree(p->kstack);
          p->kstack = 0;
          freevm(p->pgdir);
          p->state = UNUSED;
          p->pid = 0;
          p->parent = 0;
          p->name[0] = 0;
          p->killed = 0;
          release(&ptable.lock);
          return pid;
        }
      }
  
      // No point waiting if we don't have any children.
      if(!havekids || proc->killed){
        release(&ptable.lock);
        return -1;
      }
  
      // Wait for children to exit.  (See wakeup1 call in proc_exit.)
      sleep(proc, &ptable.lock);  //DOC: wait-sleep
    }
  }
  
  // Per-CPU process scheduler.
  // Each CPU calls scheduler() after setting itself up.
  // Scheduler never returns.  It loops, doing:
  //  - choose a process to run
  //  - swtch to start running that process
  //  - eventually that process transfers control
  //      via swtch back to the scheduler.
  void
  scheduler(void)
  {
    struct proc *p;
  
    for(;;){
      int winner = 0;
      int counter = 0;
      int totalTickets = 0;
      // Enable interrupts on this processor.
      sti();
      acquire(&ptable.lock);
      for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
      {
        if(p->state == RUNNABLE)
          totalTickets += p->numTickets;
      }
          
      if(totalTickets > 0)
      {
        winner = rand() % totalTickets + 1;
      }
  
      // Loop over process table looking for process to run.
      for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
        if(p->state != RUNNABLE)
          continue;
        if(p->state == RUNNABLE && counter < winner) 
        { 		
          counter += p->numTickets;
          if (counter >= winner)
            goto run;
          continue;
        }
  
        // Switch to chosen process.  It is the process's job
        // to release ptable.lock and then reacquire it
        // before jumping back to us.
        run:
        proc = p;
        switchuvm(p);
        p->state = RUNNING;
        p->numTicks += 1;
        swtch(&cpu->scheduler, proc->context);
        switchkvm();
  
        // Process is done running for now.
        // It should have changed its p->state before coming back.
        proc = 0;
      }
      release(&ptable.lock);
  
    }
  }
  
  // Enter scheduler.  Must hold only ptable.lock
  // and have changed proc->state.
  void
  sched(void)
  {
    int intena;
  
    if(!holding(&ptable.lock))
      panic("sched ptable.lock");
    if(cpu->ncli != 1)
      panic("sched locks");
    if(proc->state == RUNNING)
      panic("sched running");
    if(readeflags()&FL_IF)
      panic("sched interruptible");
    intena = cpu->intena;
    swtch(&proc->context, cpu->scheduler);
    cpu->intena = intena;
  }
  
  // Give up the CPU for one scheduling round.
  void
  yield(void)
  {
    acquire(&ptable.lock);  //DOC: yieldlock
    proc->state = RUNNABLE;
    sched();
    release(&ptable.lock);
  }
  
  // A fork child's very first scheduling by scheduler()
  // will swtch here.  "Return" to user space.
  void
  forkret(void)
  {
    // Still holding ptable.lock from scheduler.
    release(&ptable.lock);
    
    // Return to "caller", actually trapret (see allocproc).
  }
  
  // Atomically release lock and sleep on chan.
  // Reacquires lock when awakened.
  void
  sleep(void *chan, struct spinlock *lk)
  {
    if(proc == 0)
      panic("sleep");
  
    if(lk == 0)
      panic("sleep without lk");
  
    // Must acquire ptable.lock in order to
    // change p->state and then call sched.
    // Once we hold ptable.lock, we can be
    // guaranteed that we won't miss any wakeup
    // (wakeup runs with ptable.lock locked),
    // so it's okay to release lk.
    if(lk != &ptable.lock){  //DOC: sleeplock0
      acquire(&ptable.lock);  //DOC: sleeplock1
      release(lk);
    }
  
    // Go to sleep.
    proc->chan = chan;
    proc->state = SLEEPING;
    sched();
  
    // Tidy up.
    proc->chan = 0;
  
    // Reacquire original lock.
    if(lk != &ptable.lock){  //DOC: sleeplock2
      release(&ptable.lock);
      acquire(lk);
    }
  }
  
  // Wake up all processes sleeping on chan.
  // The ptable lock must be held.
  static void
  wakeup1(void *chan)
  {
    struct proc *p;
  
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
      if(p->state == SLEEPING && p->chan == chan)
        p->state = RUNNABLE;
  }
  
  // Wake up all processes sleeping on chan.
  void
  wakeup(void *chan)
  {
    acquire(&ptable.lock);
    wakeup1(chan);
    release(&ptable.lock);
  }
  
  // Kill the process with the given pid.
  // Process won't exit until it returns
  // to user space (see trap in trap.c).
  int
  kill(int pid)
  {
    struct proc *p;
  
    acquire(&ptable.lock);
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
      if(p->pid == pid){
        p->killed = 1;
        // Wake process from sleep if necessary.
        if(p->state == SLEEPING)
          p->state = RUNNABLE;
        release(&ptable.lock);
        return 0;
      }
    }
    release(&ptable.lock);
    return -1;
  }
  
  // Print a process listing to console.  For debugging.
  // Runs when user types ^P on console.
  // No lock to avoid wedging a stuck machine further.
  void
  procdump(void)
  {
    static char *states[] = {
    [UNUSED]    "unused",
    [EMBRYO]    "embryo",
    [SLEEPING]  "sleep ",
    [RUNNABLE]  "runble",
    [RUNNING]   "run   ",
    [ZOMBIE]    "zombie"
    };
    int i;
    struct proc *p;
    char *state;
    uint pc[10];
    
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
      if(p->state == UNUSED)
        continue;
      if(p->state >= 0 && p->state < NELEM(states) && states[p->state])
        state = states[p->state];
      else
        state = "???";
      cprintf("%d %s %s", p->pid, state, p->name);
      if(p->state == SLEEPING){
        getcallerpcs((uint*)p->context->ebp+2, pc);
        for(i=0; i<10 && pc[i] != 0; i++)
          cprintf(" %p", pc[i]);
      }
      cprintf("\n");
    }
  }
  
  int settickets(int tickets)
  {
    // Set the tickets
    proc->numTickets = tickets;
    return proc->numTickets;
  }
  
  int getpinfo(struct pstat *table){
    struct proc *p;
  	int i = 0;
  	acquire(&ptable.lock);
  	for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
  	{
  		if(p->state == ZOMBIE || p->state == EMBRYO)
  		{
  			continue;
  		}
  		if(p->state == UNUSED)
  		{
  			table->inuse[i] = 0;
  		}
  		else
  		{
  			table->inuse[i] = 1;
  		}
  		table->pid[i] = p->pid;
  		table->tickets[i] = p->numTickets;
  		table->ticks[i] = p->numTicks;
  		i++;
  	}
  	release(&ptable.lock);
    return 1;
  }
  
  
  