Question 23: Consider the following code for allocproc. Assuming no c…

1 1  static struct proc*
2 2  allocproc(void)
3 3  {
4 4    struct proc *p;
5 5
6 6    for(p = proc; p < &proc[NPROC]; p++) {
7 7      acquire(&p->lock);
8 8      if(p->state == UNUSED) {
9 9        goto found;
1010      } else {
1111        release(&p->lock);
1212      }
1313    }
1414    return 0;
1515
1616  found:
1717    p->pid = allocpid();
1818    p->state = USED;
1919
2020    if((p->trapframe = (struct trapframe *)kalloc()) == 0){
2121      freeproc(p);
2222      release(&p->lock);
2323      return 0;
2424    }
2525
2626    p->pagetable = proc_pagetable(p);
2727    if(p->pagetable == 0){
2828      freeproc(p);
2929      release(&p->lock);
3030      return 0;
3131    }
3232
3333    memset(&p->context, 0, sizeof(p->context));
3434    p->context.ra = (uint64)forkret;
3535    p->context.sp = p->kstack + PGSIZE;
3636
3737    return p;
3838  }