proc.c

#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "x86.h"
#include "proc.h"
#include "spinlock.h"
#include <stddef.h>
struct {
  struct spinlock lock;
  struct proc proc[NPROC];
} ptable;

static struct proc *initproc;

int nextpid = 1;
int schedPolicy = 0;

extern void forkret(void);
extern void trapret(void);

static void wakeup1(void *chan);

struct spinlock threadLock; //lock for growing address space
int random_at_most(int max);
int lottery_Total(void);

void
pinit(void)
{
  initlock(&ptable.lock, "ptable");
  initlock(&threadLock, "threadLock"); //read the details!
}

// Must be called with interrupts disabled
int
cpuid() {
  return mycpu()-cpus;
}

// Must be called with interrupts disabled to avoid the caller being
// rescheduled between reading lapicid and running through the loop.
struct cpu*
mycpu(void)
{
  int apicid, i;
  
  if(readeflags()&FL_IF)
    panic("mycpu called with interrupts enabled\n");
  
  apicid = lapicid();
  // APIC IDs are not guaranteed to be contiguous. Maybe we should have
  // a reverse map, or reserve a register to store &cpus[i].
  for (i = 0; i < ncpu; ++i) {
    if (cpus[i].apicid == apicid)
      return &cpus[i];
  }
  panic("unknown apicid\n");
}

// Disable interrupts so that we are not rescheduled
// while reading proc from the cpu structure
struct proc*
myproc(void) {
  struct cpu *c;
  struct proc *p;
  pushcli();
  c = mycpu();
  p = c->proc;
  popcli();
  return p;
}

//PAGEBREAK: 32
// 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->stackTop = -1;
  p->threads = -1;
  p->ctime = ticks;
  p->retime = 0;
  p->rutime = 0;
  p->stime = 0;
  p->priority = 3; //default value of priority
  p->qua = 0; 
  p->tickets = 10;
  release(&ptable.lock);

  // Allocate kernel stack.
  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;
}

//PAGEBREAK: 32
// Set up first user process.
void
userinit(void)
{
  struct proc *p;
  extern char _binary_initcode_start[], _binary_initcode_size[];

  p = allocproc();
  
  initproc = p;
  if((p->pgdir = setupkvm()) == 0)
    panic("userinit: out of memory?");
  inituvm(p->pgdir, _binary_initcode_start, (int)_binary_initcode_size);
  p->sz = PGSIZE;
  // ####
  p->ctime = ticks;

  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("/");

  // this assignment to p->state lets other cores
  // run this process. the acquire forces the above
  // writes to be visible, and the lock is also needed
  // because the assignment might not be atomic.
  acquire(&ptable.lock);

  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;
  struct proc *curproc = myproc();

  acquire(&threadLock); //lock the threadLock
  sz = curproc->sz;
  if(n > 0){
    if((sz = allocuvm(curproc->pgdir, sz, sz + n)) == 0){
      release(&threadLock);
      return -1;
    }
  } else if(n < 0){
    if((sz = deallocuvm(curproc->pgdir, sz, sz + n)) == 0){
      release(&threadLock);
      return -1;
    }
  }
  curproc->sz = sz; //update the size of current process
  acquire(&ptable.lock);
  //we want to update sz in all threads
  struct proc *p;
  int numberOfChildren;
  if(curproc->threads == -1){ //child thread
    //we have to update parent and sibilings
    curproc->parent->sz = curproc->sz; //update parent sz
    numberOfChildren = curproc->parent->threads - 2; //number or its sibilings
    if(numberOfChildren <= 0){
      //doesn't have sibilings
      release(&ptable.lock);
      release(&threadLock);
      switchuvm(curproc);
      return 0;
    }
    else{
      //have sibilings
      for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
        if(p != curproc && p->parent == curproc->parent && p->threads == -1){
          p->sz = curproc->sz;
          numberOfChildren--;
        }
      }
    }
  }
  else{
    //parent
    numberOfChildren = curproc->threads - 1;
    if(numberOfChildren <= 0){
      //have no children
      release(&ptable.lock);
      release(&threadLock);
      switchuvm(curproc);
      return 0;
    }
    else{
      //have chilren which we should update there size
      for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
        if(p->parent == curproc && p->threads == -1){
          p->sz = curproc->sz;
          numberOfChildren--;
        }
      }
    }

  }
  release(&ptable.lock);
  release(&threadLock);
  switchuvm(curproc);
  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 proc *curproc = myproc();

  // Allocate process.
  if((np = allocproc()) == 0){
    return -1;
  }

  // Copy process state from proc.
  if((np->pgdir = copyuvm(curproc->pgdir, curproc->sz)) == 0){
    kfree(np->kstack);
    np->kstack = 0;
    np->state = UNUSED;
    return -1;
  }
  np->sz = curproc->sz;
  np->parent = curproc;
  np->threads = 1; //the new process is a child process.
  *np->tf = *curproc->tf;

  // Clear %eax so that fork returns 0 in the child.
  np->tf->eax = 0;

  for(i = 0; i < NOFILE; i++)
    if(curproc->ofile[i])
      np->ofile[i] = filedup(curproc->ofile[i]);
  np->cwd = idup(curproc->cwd);

  safestrcpy(np->name, curproc->name, sizeof(curproc->name));

  pid = np->pid;

  acquire(&ptable.lock);

  np->state = RUNNABLE;

  release(&ptable.lock);

  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 *curproc = myproc();
  struct proc *p;
  int fd;

  if(curproc == initproc)
    panic("init exiting");

  // Close all open files.
  for(fd = 0; fd < NOFILE; fd++){
    if(curproc->ofile[fd]){
      fileclose(curproc->ofile[fd]);
      curproc->ofile[fd] = 0;
    }
  }

  begin_op();
  iput(curproc->cwd);
  end_op();
  curproc->cwd = 0;

  acquire(&ptable.lock);

  // Parent might be sleeping in wait().
  wakeup1(curproc->parent);

  // Pass abandoned children to init.
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->parent == curproc){
      p->parent = initproc;
      if(p->state == ZOMBIE)
        wakeup1(initproc);
    }
  }

  // Jump into the scheduler, never to return.
  curproc->state = ZOMBIE;
  // ####
  curproc->ttime = ticks;

  sched();
  panic("zombie exit");
}

int
check_pgdir_share(struct proc *process){
  struct proc *p;
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p != process && p->pgdir == process->pgdir)
      return 0; //there is still a thread with the same pgdir
  }
  return 1; //it's okay to free pgdir
}

// 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;
  struct proc *curproc = myproc();
  
  acquire(&ptable.lock);
  for(;;){
    // Scan through table looking for exited children.
    havekids = 0;
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
      if(p->parent != curproc)
        continue;
      if(p->threads == -1)
        continue; //it is a child thread! not a process!
      havekids = 1;
      if(p->state == ZOMBIE){
        // Found one.
        pid = p->pid;
        kfree(p->kstack);
        p->kstack = 0;
        if(check_pgdir_share(p)) //there is still threads running
          freevm(p->pgdir);
        p->pid = 0;
        p->parent = 0;
        p->name[0] = 0;
        p->killed = 0;
        p->state = UNUSED;

        //reset stackTop and pgdir
        p->stackTop = -1;
        p->pgdir = 0;
        p->threads = -1;

        release(&ptable.lock);
        return pid;
      }
    }

    // No point waiting if we don't have any children.
    if(!havekids || curproc->killed){
      release(&ptable.lock);
      return -1;
    }

    // Wait for children to exit.  (See wakeup1 call in proc_exit.)
    sleep(curproc, &ptable.lock);  //DOC: wait-sleep
  }
}
int wait2(int *retime, int *rutime, int *stime) {
  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 != myproc())
        continue;
      havekids = 1;
      if(p->state == ZOMBIE){
        // Found one.
        *retime = p->retime;
        *rutime = p->rutime;
        *stime = p->stime;
        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;
        p->ctime = 0;
        p->retime = 0;
        p->rutime = 0;
        p->stime = 0;
        p->priority = 0;
        release(&ptable.lock);
        return pid;
      }
    }

    // No point waiting if we don't have any children.
    if(!havekids || myproc()->killed){
      release(&ptable.lock);
      return -1;
    }

    // Wait for children to exit.  (See wakeup1 call in proc_exit.)
    sleep(myproc(), &ptable.lock);  //DOC: wait-sleep
  }
}


struct proc* findReadyProcess(int *index1, int *index2, int *index3, int *index4, int *index5, int *index6,uint *priority) {
  int i;
  struct proc* proc2;
notfound:
  for (i = 0; i < NPROC; i++) {
    switch(*priority) {
      case 1:
        proc2 = &ptable.proc[(*index1 + i) % NPROC];
        if (proc2->state == RUNNABLE && proc2->priority == *priority) {
          *index1 = (*index1 + 1 + i) % NPROC;
          proc2->qua=6;
          return proc2; // found a runnable process with appropriate priority
        }
      case 2:
        proc2 = &ptable.proc[(*index2 + i) % NPROC];
        if (proc2->state == RUNNABLE && proc2->priority == *priority) {
          *index2 = (*index2 + 1 + i) % NPROC;
          proc2->qua=5;
          return proc2; // found a runnable process with appropriate priority
        }
      case 3:
        proc2 = &ptable.proc[(*index3 + i) % NPROC];
        if (proc2->state == RUNNABLE && proc2->priority == *priority){
          *index3 = (*index3 + 1 + i) % NPROC;
          proc2->qua=4;
          return proc2; // found a runnable process with appropriate priority
        }
      case 4:
        proc2 = &ptable.proc[(*index1 + i) % NPROC];
        if (proc2->state == RUNNABLE && proc2->priority == *priority) {
          *index4 = (*index4 + 1 + i) % NPROC;
          proc2->qua=3;
          return proc2; // found a runnable process with appropriate priority
        }
      case 5:
        proc2 = &ptable.proc[(*index1 + i) % NPROC];
        if (proc2->state == RUNNABLE && proc2->priority == *priority) {
          *index5 = (*index5 + 1 + i) % NPROC;
          proc2->qua=2;
          return proc2; // found a runnable process with appropriate priority
       }
      case 6:
        proc2 = &ptable.proc[(*index1 + i) % NPROC];
        if (proc2->state == RUNNABLE && proc2->priority == *priority) {
          *index6 = (*index6 + 1 + i) % NPROC;
          proc2->qua=1;
          return proc2; // found a runnable process with appropriate priority
       }
    }
  }
  if (*priority == 6) {//did not find any process on any of the prorities
    *priority = 6;
    return 0;
  }
  else {
    *priority += 1; //will try to find a process at a lower priority (ighter value of priority)
    goto notfound;
  }
  return 0;
}

//PAGEBREAK: 42
// 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;
  struct cpu *c = mycpu();
  c->proc = 0;
  int count = 0;
  long golden_ticket = 0;
  int total_no_tickets = 0;
  
  for(;;){
    // Enable interrupts on this processor.
    sti();
        acquire(&ptable.lock);
       //resetting the variables to make scheduler start from the beginning of the process queue
        golden_ticket = 0;
        count = 0;
        total_no_tickets = 0;
        
        //calculate Total number of tickets for runnable processes  
        total_no_tickets = lottery_Total();

        //pick a random ticket from total available tickets
        golden_ticket = random_at_most(total_no_tickets);
    
    // Loop over process table looking for process to run.
    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){

      if(schedPolicy == 0){
        if(p->state != RUNNABLE)
          continue;
      }
      if(schedPolicy == 1){
            struct proc *highP = 0;
            struct proc *p1 = 0;
            if(p->state != RUNNABLE)
                continue;
            // Choose the process with highest priority (among RUNNABLEs)
            highP = p;
            for(p1 = ptable.proc; p1 < &ptable.proc[NPROC]; p1++){
              if((p1->state == RUNNABLE) && (highP->priority > p1->priority))
                  highP = p1;
              }

            if(highP != 0)
                p = highP;
      }
      if(schedPolicy == 2){ //Multi level 

        struct proc *foundP = 0;

            uint priority = 1;

            int index1 = 0;
            int index2 = 0;
            int index3 = 0;
            int index4 = 0;
            int index5 = 0;
            int index6 = 0;

            foundP = findReadyProcess(&index1, &index2, &index3,&index4, &index5, &index6, &priority);
            if (foundP != 0)
              p = foundP;
            else{
              if(p->state != RUNNABLE)
                continue;
            }

      }
      if(schedPolicy == 3){ //Lottery
          if(p->state != RUNNABLE)
            continue;
          //find the process which holds the lottery winning ticket 
          if ((count + p->tickets) < golden_ticket){
            count += p->tickets;
            continue;
          }
      }
    if(p!=0){
      // Switch to chosen process.  It is the process's job
      // to release ptable.lock and then reacquire it
      // before jumping back to us.
      c->proc = p;
      switchuvm(p);
      p->state = RUNNING;

      swtch(&(c->scheduler), p->context);
      switchkvm();

      // Process is done running for now.
      // It should have changed its p->state before coming back.
      c->proc = 0;
            }
    }
    release(&ptable.lock);

  }
}

// Enter scheduler.  Must hold only ptable.lock
// and have changed proc->state. Saves and restores
// intena because intena is a property of this
// kernel thread, not this CPU. It should
// be proc->intena and proc->ncli, but that would
// break in the few places where a lock is held but
// there's no process.
void
sched(void)
{
  int intena;
  struct proc *p = myproc();

  if(!holding(&ptable.lock))
    panic("sched ptable.lock");
  if(mycpu()->ncli != 1)
    panic("sched locks");
  if(p->state == RUNNING)
    panic("sched running");
  if(readeflags()&FL_IF)
    panic("sched interruptible");
  intena = mycpu()->intena;
  swtch(&p->context, mycpu()->scheduler);
  mycpu()->intena = intena;
}

// Give up the CPU for one scheduling round.
void
yield(void)
{
  acquire(&ptable.lock);  //DOC: yieldlock
  myproc()->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)
{
  static int first = 1;
  // Still holding ptable.lock from scheduler.
  release(&ptable.lock);

  if (first) {
    // Some initialization functions must be run in the context
    // of a regular process (e.g., they call sleep), and thus cannot
    // be run from main().
    first = 0;
    iinit(ROOTDEV);
    initlog(ROOTDEV);
  }

  // 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)
{
  struct proc *p = myproc();
  
  if(p == 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.
  p->chan = chan;
  p->state = SLEEPING;

  sched();

  // Tidy up.
  p->chan = 0;

  // Reacquire original lock.
  if(lk != &ptable.lock){  //DOC: sleeplock2
    release(&ptable.lock);
    acquire(lk);
  }
}

//PAGEBREAK!
// 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;
}

//PAGEBREAK: 36
// 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 
getTicks(void){
  cprintf("%d\n", ticks);
  return 0;
}

int 
getProcInfo(void){
  struct proc *p;
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->state == RUNNING){
      cprintf("#pid = %d, create time = %d\n", p->pid, p->ctime);
    }
    // if(p->state == SLEEPING){
    //   cprintf("-pid = %d, create time = %d\n", p->pid, p->ctime);
    // }
  }
  return 0;
}

int
thread_create(void *stack)
{
  int i, pid;
  struct proc *np; //new process
  struct proc *curproc = myproc();

  // Allocate process.
  if((np = allocproc()) == 0){
    return -1;
  }
  //incerase thread numbers for parent (default for child is -1)
  curproc->threads++;

  //grow downwards
  np->stackTop = (int)((char*)stack + PGSIZE);
  acquire(&ptable.lock); 
  np->pgdir = curproc->pgdir;  //page directory
  np->sz = curproc->sz; //size of thread
  release(&ptable.lock);

  int bytesOnStack = curproc->stackTop - curproc->tf->esp;
  np->tf->esp = np->stackTop - bytesOnStack;
  memmove((void*)np->tf->esp, (void*)curproc->tf->esp, bytesOnStack);
  np->parent = curproc;

  // copy all trap frame register values from p into newp
  *np->tf = *curproc->tf;
  // Clear %eax so that fork returns 0 in the child because we had copied all parent data in child and fork return value for parent was child PID 
  np->tf->eax = 0;
  // esp is stack pointer (update it to grow down on the size of bytes)
  np->tf->esp = np->stackTop - bytesOnStack;
  // ebp is the base pointer
  np->tf->ebp = np->stackTop - (curproc->stackTop - curproc->tf->ebp);

  for(i = 0; i < NOFILE; i++)
    if(curproc->ofile[i])
      np->ofile[i] = filedup(curproc->ofile[i]);
  np->cwd = idup(curproc->cwd);

  safestrcpy(np->name, curproc->name, sizeof(curproc->name));

  pid = np->pid;

  acquire(&ptable.lock);

  np->state = RUNNABLE;

  release(&ptable.lock);

  return pid;
}

int
thread_join(int input_pid)
{
  acquire(&threadLock); 
  int flag = 0;
  struct proc *p;
  // search for thread
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if((p->pid) == input_pid){
      flag = 1;
      break;
    }
  }
  release(&threadLock);

  if(flag == 0)
    return -1;

  acquire(&ptable.lock);
  for(;;){
      if(p->state == ZOMBIE){
        // Found one.
        kfree(p->kstack);
        p->kstack = 0;
        if(check_pgdir_share(p)){ //check if there are still some threads left with this pagedir
          freevm(p->pgdir);
        }
        p->pid = 0;
        p->parent = 0;
        p->name[0] = 0;
        p->killed = 0;
        p->state = UNUSED;
        p->stackTop = 0;
        p->pgdir = 0;
        p->threads = -1;
        release(&ptable.lock);
        return 0;
      }

    // No point waiting if we don't have any children.
    if(p->killed){
      release(&ptable.lock);
      return -1;
    }
    // Wait for children to exit.  (See wakeup1 call in proc_exit.)
    sleep(p->parent, &ptable.lock);  //DOC: wait-sleep
  }
}

int
thread_id(void)
{
  struct proc *curproc = myproc();
  return curproc->pid;
}

void updateStatus() {
  struct proc *p;
  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    switch(p->state) {
      case RUNNABLE:
        p->retime++;
        break;
      case SLEEPING:
        p->stime++;
        break;
      case RUNNING:
        p->rutime++;
        break;
      default:
        ;
    }
  }
  release(&ptable.lock);
}


int
setPriority(int priority, int pid){
  struct proc *p;
  if(priority<1 || priority>6){
    priority = 5;
  }
  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->pid == pid){
      p->priority = priority;
    }
  }
  release(&ptable.lock);
  return 0;
}

int
getPriority(int pid){
  struct proc *p;
  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->pid == pid){
      // cprintf("priority for %d is %d\n", pid, p->priority);
      return p->priority;
    }
  }
  release(&ptable.lock);
  return 0;
}

uint
getctime(int pid){
  struct proc *p;
  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->pid == pid){
      return p->ctime;
    }
  }
  release(&ptable.lock);
  return 0;
}

int
getttime(int pid){
  struct proc *p;
  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->pid == pid){
      return p->ttime;
    }
  }
  release(&ptable.lock);
  return 0;
}

int
getrutime(int pid){
  struct proc *p;
  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->pid == pid){
      return p->rutime;
    }
  }
  release(&ptable.lock);
  return 0;
}


int
getProcStatus(int type, int pid) {
    struct proc *proc = myproc();
    if (pid != -1) {
        acquire(&ptable.lock);
        struct proc *p;
        for (p = ptable.proc; p < &ptable.proc[NPROC]; p++) {
            if (p->pid == pid) {
                proc = p;
                break;
            }
        }
        release(&ptable.lock);
    }
    switch (type) {
        //ctime
        case 1:
            return proc->ctime;
        //ttime
        case 2:
            return proc->ttime;
        //rutime
        case 3:
            return proc->rutime;
        //retime
        case 4:
            return proc->retime;
        //stime
        case 5:
            return proc->stime;
    }
    return 0;
}

int
changePolicy(int schedNum){
  schedPolicy = schedNum;
  return 0;
}

int 
lottery_Total(void){
  struct proc *p;
  int ticket_aggregate=0;

//loop over process table and increment total tickets if a runnable process is found 
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
  {
    if(p->state==RUNNABLE){
      ticket_aggregate+=p->tickets;
    }
  }
  return ticket_aggregate;          // returning total number of tickets for runnable processes
}

/* This method is used to generate a random number, between 0 and M
This is a modified version of the LFSR alogrithm
found here: http://goo.gl/At4AIC */
int
random_at_most(int max) {

  if(max <= 0) {
    return 1;
  }

  static int z1 = 12345; // 12345 for rest of zx
  static int z2 = 12345; // 12345 for rest of zx
  static int z3 = 12345; // 12345 for rest of zx
  static int z4 = 12345; // 12345 for rest of zx

  int b;
  b = (((z1 << 6) ^ z1) >> 13);
  z1 = (((z1 & 4294967294) << 18) ^ b);
  b = (((z2 << 2) ^ z2) >> 27);
  z2 = (((z2 & 4294967288) << 2) ^ b);
  b = (((z3 << 13) ^ z3) >> 21);
  z3 = (((z3 & 4294967280) << 7) ^ b);
  b = (((z4 << 3) ^ z4) >> 12);
  z4 = (((z4 & 4294967168) << 13) ^ b);

  // if we have an argument, then we can use it
  int rand = ((z1 ^ z2 ^ z3 ^ z4)) % max;

  if(rand < 0) {
    rand = rand * -1;
  }

  return rand;
}

// Change Process tickets
int
changeTickets(int tickets, int pid)
{
  struct proc *p;

  acquire(&ptable.lock);
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->pid == pid) {
        p->tickets = tickets;
        break;
    }
  }
  release(&ptable.lock);

  return pid;
}