my_pthread.c:

  In HP-UX-10.20 and other old Posix 1003.4a Draft 4 implementations

  pthread_mutex_trylock returns 1 on success, not 0 like

  pthread_mutex_lock

  From the HP-UX-10.20 man page:

  RETURN VALUES

      If the function fails, errno may be set to one of the following

      values:

           Return | Error    | Description

           _______|__________|_________________________________________

              1   |          | Successful completion.

              0   |          | The mutex is  locked; therefore, it was

                  |          | not acquired.

             -1   | [EINVAL] | The value specified by mutex is invalid.

*/

/* We defined pthread_mutex_trylock as a macro in my_pthread.h, we have

   to undef it here to prevent infinite recursion! Note that this comment

   documents the pushed bugfix, not just the the code itself here. That is why

   this comment is good here.

*/

#undef pthread_mutex_trylock

/*

This function returns 0 if we are able successfully lock the mutex. If

the mutex cannot be locked or there is an error, then returns != 0

*/

int my_pthread_mutex_trylock(pthread_mutex_t *mutex)

{

  int error = pthread_mutex_trylock(mutex);

  if (error == 1)			/* Safety if the lib is fixed */

    return 0;				/* Mutex was locked */

  if (error == -1)			/* Safety if the lib is fixed */

    error=errno;

   return error;

  if (error == 1)

    return 0;           /* success */

  if (error == -1)

    error=errno;        /* parameter invalid */

  return 1;             /* we were not able to lock the mutex */

}

#endif