#include "futex.h"

#include "machine.h"

#include "system.h"

#include "vdl-alloc.h"

struct Futex *futex_new (void)

{

  struct Futex *futex = vdl_alloc_new (struct Futex);

  futex_construct (futex);

  return futex;

}

void futex_delete (struct Futex *futex)

{

  futex_destruct (futex);

  vdl_alloc_delete (futex);

}

void futex_construct (struct Futex *futex)

{

  futex->state = 0;

}

void futex_destruct (struct Futex *futex)

{}

void futex_lock (struct Futex *futex)

{

  uint32_t c;

  if ((c = machine_atomic_compare_and_exchange (&futex->state, 0, 1)) != 0)

    {

      do {

	if (c == 2 || machine_atomic_compare_and_exchange (&futex->state, 1, 2) != 0)

	  {

	    system_futex_wait (&futex->state, 2);

	  }

      } while ((c = machine_atomic_compare_and_exchange (&futex->state, 0, 2)) != 0);

    }

}

void futex_unlock (struct Futex *futex)

{

  if (machine_atomic_dec (&futex->state) != 1) 

    {

      futex->state = 0;

      system_futex_wake (&futex->state, 1);

    }

}