source: bootcd/isolinux/syslinux-6.03/core/thread/start_thread.c

#include <string.h>
#include <stdlib.h>
#include <com32.h>
#include "core.h"
#include "thread.h"

#define REAL_MODE_STACK_SIZE    4096
#define MIN_STACK_SIZE          16384
#define THREAD_ALIGN            64      /* Thread alignment */

extern void __start_thread(void);

struct thread *start_thread(const char *name, size_t stack_size, int prio,
                            void (*start_func)(void *), void *func_arg)
{
    irq_state_t irq;
    struct thread *curr, *t;
    char *stack, *rmstack;
    const size_t thread_mask = THREAD_ALIGN - 1;
    struct thread_stack *sp;

    if (stack_size < MIN_STACK_SIZE)
        stack_size = MIN_STACK_SIZE;

    stack_size = (stack_size + thread_mask) & ~thread_mask;
    stack = malloc(stack_size + sizeof(struct thread));
    if (!stack)
        return NULL;
    rmstack = lmalloc(REAL_MODE_STACK_SIZE);
    if (!rmstack) {
        free(stack);
        return NULL;
    }

    t = (struct thread *)stack;
    memset(t, 0, sizeof *t);
    t->stack   = stack;
    t->rmstack = rmstack;
    stack += sizeof(struct thread);

    /* sp allocated from the end of the stack */
    sp = (struct thread_stack *)(stack + stack_size) - 1;
    t->esp = sp;

    sp->errno = 0;
    sp->rmss = SEG(rmstack);
    sp->rmsp = REAL_MODE_STACK_SIZE;
    sp->esi = (size_t)start_func;
    sp->edi = (size_t)func_arg;
    sp->ebx = irq_state();      /* Inherit the IRQ state from the spawner */
    sp->eip = __start_thread;
    t->prio = prio;
    t->name = name;

    irq = irq_save();
    curr = current();

    t->thread_magic    = THREAD_MAGIC;

    t->list.prev       = &curr->list;
    t->list.next       = curr->list.next;
    curr->list.next    = &t->list;
    t->list.next->prev = &t->list;

    __schedule();

    irq_restore(irq);
    return t;
}