message: Fix waitpid deadlock.
diff: @@ -228,6 +228,12 @@ fn fork_inner(initial_rsp: *mut usize) -> Result<usize> {
  // Unblock context.
  syscall::kill(new_pid, SIGCONT)?;
  + // XXX: Killing with SIGCONT will put (pid, 65536) at key (pid, pgid) into the waitpid of this
  + // context. This means that if pgid is changed (as it is in ion for example), the pgid message
  + // in syscall::exit() will not be inserted as the key comparator thinks they're equal as their
  + // PIDs are. So, we have to call this to clear the waitpid queue to prevent deadlocks.
  + let _ = syscall::waitpid(new_pid, &mut 0, syscall::WUNTRACED | syscall::WCONTINUED);
  +
  Ok(new_pid)
  }
  #[no_mangle]
  