bug: attempting to resume the running coroutine makes it unyieldable

ldo.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ldo.c,v 2.110 2013/08/27 18:53:35 roberto Exp roberto $
+** $Id: ldo.c,v 2.111 2013/09/17 15:40:06 roberto Exp roberto $
 ** Stack and Call structure of Lua
 ** See Copyright Notice in lua.h
 */
@@ -538,6 +538,7 @@ static void resume (lua_State *L, void *ud) {
 
 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
   int status;
+  int oldnny = L->nny;  /* save 'nny' */
   lua_lock(L);
   luai_userstateresume(L, nargs);
   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
@@ -559,7 +560,7 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
     }
     lua_assert(status == L->status);
   }
-  L->nny = 1;  /* do not allow yields */
+  L->nny = oldnny;  /* restore 'nny' */
   L->nCcalls--;
   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
   lua_unlock(L);