mutex and condition variable implementation using futex

I have implemented mutex and contition variables using futex syscall. I believe that my implementation is correct, but would like it to be verified by some one else. If some of you could verify its correctness, it would be a great help.

Any suggestions for further improvements in the performance of the mutex and contition variables would also be appreciated.

  #ifndef __SYNCHRONIZATION__
  #define __SYNCHRONIZATION__

  #include <unistd.h>
  #include <limits.h>
  #include <sys/syscall.h>
  #include <linux/futex.h>
  #include "types.h"
  #include "assembly.h"

  typedef UINT32 mutex;
  typedef struct condvar condvar;

  struct condvar    {
   mutex *m;
   int seq;
  };

  void mutex_init(mutex *m) {
   *m = 0;
  }

  void mutex_destroy(mutex *m)  {
   *m = 0;
  }

  void mutex_lock(mutex *m) {
   UINT32 c;
   if((c = __sync_val_compare_and_swap(m, 0, 1)) != 0)  {
    do  {
        if((c == 2) || __sync_val_compare_and_swap(m, 1, 2) != 0)
            syscall(SYS_futex, m, FUTEX_WAIT_PRIVATE, 2, NULL, NULL, 0);
    } while((c = __sync_val_compare_and_swap(m, 0, 2)) != 0);
   }
  }

  void mutex_unlock(mutex *m)   {
   if(__sync_fetch_and_sub(m, 1) != 1)  {
    *m = 0;
    syscall(SYS_futex, m, FUTEX_WAKE_PRIVATE, 1, NULL, NULL, 0);
   }
  }

  void cond_init(condvar *c, mutex *m)  {
   c->m = m;
   c->seq = 0;
  }

  void cond_destroy(condvar *c) {
   c->m = NULL;
   c->seq = 0;
  }

  void cond_signal(condvar *c)  {
   __sync_fetch_and_add(&(c->seq), 1);
   syscall(SYS_futex, &(c->seq), FUTEX_WAKE_PRIVATE, 1, NULL, NULL, 0);
  }

  void cond_broadcast(condvar *c)   {
   __sync_fetch_and_add(&(c->seq), 1);
   syscall(SYS_futex, &(c->seq), FUTEX_REQUEUE_PRIVATE, 1, (void *) INT_MAX, c->m, 0);
  }

  void cond_wait(condvar *c)    {
   UINT32 oldSeq = c->seq;
   mutex_unlock(c->m);
   syscall(SYS_futex, &(c->seq), FUTEX_WAIT_PRIVATE, oldSeq, NULL, NULL, 0);
   while (xchg32(c->m, 2))  {
    syscall(SYS_futex, c->m, FUTEX_WAIT_PRIVATE, 2, NULL, NULL, 0);
   }
  }

  #endif

Thanks

Sudhanshu