Subj : Adding threads to a doublelinked list
To   : comp.programming.threads
From : JS
Date : Tue Apr 19 2005 11:48 am

This function creates a thread. I have also made a double-linked list that a
thread should be added to when it is created. But I don't know when I
should add it to this list.

I have tried to add it just after I use malloc but I am not sure that is
right.

#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>

typedef int mythread_t;

typedef struct _mythread_attr_t {
} mythread_attr_t;

#define STACK_SIZE 1024


struct pcb {
  void *(*start_routine) (void *);
  void *arg;
  jmp_buf state;
  int    stack[STACK_SIZE];
};

static struct pcb first_thread;

struct pcb *current = &first_thread;
struct pcb *ready = NULL; /* Vi har ikke en ventende tråd endnu */


int mythread_create (mythread_t *threadp,
                    const mythread_attr_t *attr,
                    void *(*start_routine) (void *),
                    void *arg)
{
  int *state_pointer;
  int local_occ;
  struct pcb *pcb_pointer;
  
  pcb_pointer = (struct pcb *) malloc(sizeof(struct pcb));
  if(pcb_pointer == NULL) {
     exit(-1);
  }

  pcb_pointer->start_routine = start_routine;
  pcb_pointer->arg = arg;
  
  if(setjmp(pcb_pointer->state)) {
    
    current->start_routine(current->arg);
    printf("Thread has returned - Stop everything\n");
    exit(0);
  }


  state_pointer = (int *) &pcb_pointer->state;
  local_occ = state_pointer[JB_BP] - state_pointer[JB_SP];
  state_pointer[JB_BP] = (int) (pcb_pointer->stack + STACK_SIZE);
  state_pointer[JB_SP] = (int) state_pointer[JB_BP] - local_occ;


  ready = pcb_pointer;


  *threadp = (int) pcb_pointer;

  return 0;
}

.