#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdint.h>
#include <errno.h>

static void NoPause(void *ud)
{
    (void)ud;
}

typedef int dint;
typedef const char* LOCK;
void (*pauseCB)(void *) = NoPause;

static void LockSiData( LOCK **shared, LOCK *ptr )
{
    while ( *shared != ptr )
    {
        if ( !(*shared) )
            *shared = ptr;
        pauseCB( ptr );
    }
}

static dint FreeSiData( LOCK **shared, LOCK *ud )
{
    if ( *shared == ud )
    {
        *shared = NULL;
        return 0;
    }
    return EPERM;
}

static LOCK *l = 0;
static volatile int var = 0;

static void *thread(void *arg)
{
    int i;
    while (1) {
        LockSiData(&l, arg);
        i = var++;
        if (i != 0) {
            printf("var = %d, expected 0\n", i);
            exit(1);
        }
        i = var--;
        if (i != 1) {
            printf("var = %d, expected 1\n", i);
            exit(1);
        }
        FreeSiData(&l, arg);
    }
    return 0;
}

int main(void)
{
    pthread_t pt;
    uintptr_t i;

    for (i = 1; i <= 2; i++) {
        if ((errno = pthread_create(&pt, 0, thread, (void *)i)) != 0) {
            printf("pthread_create failed: %m\n");
            return 1;
        }
    }
    pthread_exit(0);
    return 0;
}