The dtrace_open() call modifies the minor device value that is passed to it by 
reference. Since the reference is coming from the io_func_attr pointer passed 
to the resource manager's open() handler, the change propagates to the 
/dev/dtrace/dtrace node, preventing it from being opened again (dtrace_open()
rejects an attempt to open a node with a minor number other than 0).
The fix is to duplicate the attribute structure and pass that to dtrace_open().