don't let kill-buffer kill a buffer if it is current in any thread

src/buffer.c

@@ -1726,6 +1726,9 @@ cleaning up all windows currently displaying the buffer to be killed. */)
   if (!BUFFER_LIVE_P (b))
     return Qnil;
 
+  if (thread_check_current_buffer (b))
+    return Qnil;
+
   /* Query if the buffer is still modified.  */
   if (INTERACTIVE && !NILP (BVAR (b, filename))
       && BUF_MODIFF (b) > BUF_SAVE_MODIFF (b))

src/thread.c

@@ -881,6 +881,25 @@ DEFUN ("all-threads", Fall_threads, Sall_threads, 0, 0, 0,
 
 
 
+int
+thread_check_current_buffer (struct buffer *buffer)
+{
+  struct thread_state *iter;
+
+  for (iter = all_threads; iter; iter = iter->next_thread)
+    {
+      if (iter == current_thread)
+	continue;
+
+      if (iter->m_current_buffer == buffer)
+	return 1;
+    }
+
+  return 0;
+}
+
+
+
 static void
 init_primary_thread (void)
 {

src/thread.h

@@ -248,4 +248,6 @@ int thread_select  (select_func *func, int max_fds, SELECT_TYPE *rfds,
 		    SELECT_TYPE *wfds, SELECT_TYPE *efds, EMACS_TIME *timeout,
 		    sigset_t *sigmask);
 
+int thread_check_current_buffer (struct buffer *);
+
 #endif /* THREAD_H */