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"

struct {
  struct spinlock lock;
  struct proc proc[NPROC];
} ptable;

static struct proc *initproc;

int nextpid = 1;
extern void forkret(void);
extern void trapret(void);

static void wakeup1(void *chan);

void
pinit(void)
{
  initlock(&ptable.lock, "ptable");

  for (int i = 0; i < 101; i++)
    queues[i] = 0;

  #ifdef RR
    cprintf("Scheduling: Round Robin\n");
  #endif
  #ifdef FCFS
    cprintf("Scheduling: First Come First Serve\n");
  #endif
  #ifdef PBS
    cprintf("Scheduling: Priority Based Scheduling\n");
  #endif
  #ifdef MLFQ
    cprintf("Scheduling: Multi Level Feedback Queue\n");
  #endif
}

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

// Loops over processes to increase waiting and io time of processes
void
inctime(void)
{
  struct proc *p;

    for (p = ptable.proc; p < &ptable.proc[NPROC]; p++) {
    if (p->state == RUNNABLE)
      p->wtime++;
    if (p->state == SLEEPING)
      p->iotime++;
  }
}

void
push(struct node **head, struct proc *p)
{
  struct node *newNode = 0;
  for (int i = 0; i < NPROC; i++) {
    if (!(nodes[i].p)) {
      newNode = &(nodes[i]);
      break;
    }
  }
  newNode->next = 0;
  newNode->p = p;

  if (!(*head)) {
    *head = newNode;
  } else {
    struct node *cur = *head;
    while (cur->next) cur = cur->next;
    cur->next = newNode;
  }
}

struct proc*
pop(struct node **head)
{
  if (!(*head)) return 0;

  struct node *del = (*head);
  *head = (*head)->next;
  struct proc *ret = del->p;
  del->p = 0;
  return ret;
}

void remove(struct node **head, int pid)
{
  if ((*head)->p->pid == pid) {
    (*head)->p = 0;
    *head = (*head)->next;
    return;
  }

  struct node *cur = *head;
  while (cur && cur->next) {
    if (cur->next->p->pid == pid) {
      struct node *del = cur->next;
      cur->next = del->next;
      del->p = 0;
      return;
    }
    cur = cur->next;
  }
}

int
set_priority(int new_priority, int pid)
{
  #ifndef PBS
    cprintf("Scheduling is not Priority Based!\n");
    return -1;
  #endif
  
  if (new_priority < 0 || new_priority > 100)
    return -1;

  acquire(&ptable.lock);
  struct proc *p;
  int old_priority = -1;

  for (p = ptable.proc; p < &ptable.proc[NPROC]; p++) {
    if (p->pid == pid) {
      old_priority = p->queue;
      p->queue = new_priority;
      if (p->qtime) {
        remove(&queues[old_priority], p->pid);
        push(&queues[new_priority], p);
      }
      break;
    }
  }

  // cprintf("Changed %d (%s) priority from %d to %d\n", p->pid, p->name, old_priority, new_priority);

  release(&ptable.lock);

  if (myproc() && new_priority < myproc()->queue)
    yield();

  return old_priority;
}

void
ps(void)
{
  struct proc *p;
  char* states[] = { "UNUSED", "EMBRYO  ", "SLEEPING", "RUNNABLE", "RUNNING ", "ZOMBIE  " };

  cprintf("PID\t");
  #ifdef PBS
    cprintf("Priority\t");
  #endif
  cprintf("State   \tr_time\tw_time\tn_run\t");
  #ifdef MLFQ
    cprintf("cur_q\t");
    for (int i = 0; i < 5; i++)
      cprintf("q%d\t", i);
  #endif
  cprintf("\n");

  acquire(&ptable.lock);

  // Loop over process table looking for process to run.
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->state == UNUSED)
      continue;

    cprintf("%d\t", p->pid);
    #ifdef PBS
      cprintf("%d\t\t", p->queue);
    #endif
    cprintf("%s\t%d\t%d\t%d\t", states[p->state], p->rtime, p->wtime, p->n_run);
    #ifdef MLFQ
      cprintf("%d\t", p->queue);
      for (int i = 0; i < 5; i++)
        cprintf("%d\t", p->q[i]);
    #endif
    cprintf("\n");
  }

  release(&ptable.lock);
}

void
assignQueue(struct proc *p) {
  if (p->queue > 4)
    p->queue = 0;
  p->qtime = ticks + 1;
  p->wtime = 0;
  push(&queues[0], p);
  #ifdef GRAPH
    if (p->pid > 3)
      cprintf("GRAPH %d %d %d\n", p->pid - 4, ticks, p->queue);
  #endif
}

// 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->ctime = ticks;
  p->etime = 0;
  p->rtime = 0;
  p->queue = 60;
  p->n_run = 0;
  p->wtime = 0;
  p->iotime = 0;
  for (int i = 0; i < 5; i++) p->q[i] = 0;

  release(&ptable.lock);

  if (1) {
    if (myproc() && 60 < myproc()->queue)
      yield();
  }

  // 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;
  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;
  #ifdef MLFQ
    assignQueue(p);
  #endif

  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();

  sz = curproc->sz;
  if(n > 0){
    if((sz = allocuvm(curproc->pgdir, sz, sz + n)) == 0)
      return -1;
  } else if(n < 0){
    if((sz = deallocuvm(curproc->pgdir, sz, sz + n)) == 0)
      return -1;
  }
  curproc->sz = sz;
  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->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;
  #ifdef MLFQ
    assignQueue(np);
  #endif

  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->etime = ticks;
  curproc->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;
  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;
      havekids = 1;
      if(p->state == ZOMBIE){
        // Found one.
        pid = p->pid;
        kfree(p->kstack);
        p->kstack = 0;
        freevm(p->pgdir);
        p->pid = 0;
        p->parent = 0;
        p->name[0] = 0;
        p->killed = 0;
        p->state = UNUSED;
        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
  }
}

// Wait for a child process to exit and return its pid.
// Return -1 if this process has no children.
// Set wtime and rtime to waiting time and running time of child
int
waitx(int* wtime, int* rtime)
{
  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;
      havekids = 1;
      if(p->state == ZOMBIE){
        // Found one.
        *rtime = p->rtime;
        *wtime = p->etime - p->ctime - p->rtime - p->iotime;
        pid = p->pid;
        kfree(p->kstack);
        p->kstack = 0;
        freevm(p->pgdir);
        p->pid = 0;
        p->parent = 0;
        p->name[0] = 0;
        p->killed = 0;
        p->state = UNUSED;
        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
  }
}

// Shifts given CPU to given process
void
shift(struct proc *p, struct cpu *c)
{
  if (!p) return;

  // 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;
  p->n_run++;
  p->wtime = 0;

  // cprintf("%d starting pid %d (%s) with ctime %d, queue %d, qtime %d at %d\n", c->apicid, p->pid, p->name, p->ctime, p->queue, p->qtime, ticks);
  
  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;
}

// Round Robin
void
scheduleRR(struct cpu *c)
{
  struct proc *p;

  // Loop over process table looking for process to run.
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->state != RUNNABLE)
      continue;

    p->allowedtime = 1;
    shift(p, c);
  }
}

// First Come First Serve
void
scheduleFCFS(struct cpu *c)
{
  struct proc *p;
  struct proc *serve = 0;

  // Loop over process table looking for process to run.
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->state != RUNNABLE)
      continue;

    if (!serve || serve->ctime > p->ctime)
      serve = p;
  }

  shift(serve, c);
}

// Priority Based Scheduler with Level 2 Round Robin
void
schedulePBS(struct cpu *c)
{
  struct proc *p;

  // Check for runnable processes not in any queue
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->state != RUNNABLE)
      continue;

    if ((p->qtime) == 0) {
      p->qtime = ticks + 1;
      push(&queues[p->queue], p);
      // cprintf("Push %d\n", p->pid);
    }
  }

  int q = 0;
  while (q < 101 && !queues[q])  q++;

  if (q == 101) return;

  p = pop(&queues[q]);
  if (q != p->queue) cprintf("ERROR !!!\n");

  p->allowedtime = 1;
  shift(p, c);

  p->qtime = 0;
}

// Multi Level Feedback Queue
void
scheduleMLFQ(struct cpu *c) {
  struct proc *p;
  struct node* cur;

  // Check for runnable processes not in any queue
  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
    if(p->state != RUNNABLE)
      continue;

    if ((p->qtime) == 0)
      assignQueue(p);
  }

  // Age the processes
  for (int i = 1; i < 5; i++) {
    cur = queues[i];
    while (cur) {
      p = cur->p;
      if (1 + ticks - p->qtime > 100) {
        remove(&queues[i], p->pid);
        p->queue = i - 1;
        p->qtime = ticks + 1;
        p->wtime = 0;
        push(&queues[i-1], p);
        #ifdef GRAPH
          if (p->pid > 3)
            cprintf("GRAPH %d %d %d\n", p->pid - 4, ticks, p->queue);
        #endif
      }
      cur = cur->next;
    }
  }

  int q = 0;
  while (q < 5 && !queues[q])  q++;

  if (q == 5) return;

  p = pop(&queues[q]);

  p->allowedtime = (1 << q);

  shift(p, c);

  p->qtime = 0;

  if (p->state == RUNNABLE) {
    if (p->allowedtime == 0 && q < 4)  q++;

    p->qtime = ticks + 1;
    p->queue = q;
    push(&queues[q], p);
  }

  #ifdef GRAPH
    if (p->pid > 3)
      cprintf("GRAPH %d %d %d\n", p->pid - 4, ticks, p->queue);
  #endif
}

//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 cpu *c = mycpu();
  c->proc = 0;
  for(;;) {
    // Enable interrupts on this processor.
    sti();
    acquire(&ptable.lock);
    
    #ifdef RR
      scheduleRR(c);
    #endif
    #ifdef FCFS
      scheduleFCFS(c);
    #endif
    #ifdef PBS
      schedulePBS(c);
    #endif
    #ifdef MLFQ
      scheduleMLFQ(c);
    #endif
    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;
      #ifdef MLFQ
        assignQueue(p);
      #endif
    }
      
}

// 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;
        #ifdef MLFQ
          assignQueue(p);
        #endif
      }
      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");
  }
}