The following code from Andreas Messer fails with an assertion when run on a system with hardware support for lock elision, and with a libc with lock elision enabled.

#include <pthread.h>
#include <time.h>

int main(int argc, char* argv[])
{
  pthread_mutex_t mutex;
  pthread_mutexattr_t attr;
  struct timespec ts;

  pthread_mutexattr_init( &attr );
  pthread_mutexattr_settype( &attr, PTHREAD_MUTEX_ERRORCHECK );
  pthread_mutex_init( &mutex, &attr );

  clock_gettime( CLOCK_REALTIME, &ts );
  ts.tv_sec += 3;
  pthread_mutex_timedlock( &mutex, &ts );
  pthread_mutex_unlock(&mutex);
  return 0;
}

It returns the following assertion:

a.out: pthread_mutex_unlock.c:87: __pthread_mutex_unlock_usercnt: Assertion `type == PTHREAD_MUTEX_ERRORCHECK_NP' failed.
Aborted

Patch will follow on the mailing list.