dlopen() deadlock

gistfile1.txt

#include <assert.h>
#include <link.h>
#include <dlfcn.h>
#include <stdio.h>
#include <pthread.h>

static int
callback(struct dl_phdr_info *info, size_t size, void *data)
{
  void *handle;

  handle = dlopen("/usr/lib/libpthread.so", RTLD_LAZY | RTLD_NOLOAD);
  //dlsym(handle, ".swift2_protocol_conformances_start");
  dlclose(handle);
  return (0);
}

void
call_me_maybe(void *args) {
  dl_iterate_phdr(callback, 0);
}

int
main(int argc, char *argv[])
{
  pthread_t thread1;

  pthread_create(&thread1, NULL, (void *) &call_me_maybe, NULL);
  pthread_join(thread1, NULL);
  return (0);
}