While playing Kim's latest string deduplication code to enable string deduplication during root scan, I got following assertion:

# assert(false) failed: Attempting to acquire lock ^H<98>¬l<8d>^?/9 out of order with lock stack_watermark_lock/2 -- possible deadlock

The first lock name should be one of OopStorage's _allocation_mutex, but it showed as garbage above.

It turns out that _allocation_mutex name is generated dynamically.

e.g.
_allocation_mutex(make_oopstorage_mutex(name, "alloc", Mutex::oopstorage)),

and

static Mutex* make_oopstorage_mutex(const char* storage_name,
                                    const char* kind,
                                    int rank) {
  char name[256];
  os::snprintf(name, sizeof(name), "%s %s lock", storage_name, kind);
  return new PaddedMutex(rank, name, true, Mutex::_safepoint_check_never);
}