barrier for prototype's cache (with new gray list 'protogray' to keep

prototypes to have their caches visited again) + constant 'MAXMISS'

lvm.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.c,v 2.274 2017/04/28 20:57:45 roberto Exp roberto $
+** $Id: lvm.c,v 2.275 2017/04/30 20:43:26 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -626,9 +626,7 @@ static LClosure *getcached (Proto *p, UpVal **encup, StkId base) {
 
 /*
 ** create a new Lua closure, push it in the stack, and initialize
-** its upvalues. Note that the closure is not cached if prototype is
-** already black (which means that 'cache' was already cleared by the
-** GC).
+** its upvalues. ???
 */
 static void pushclosure (lua_State *L, Proto *p, UpVal **encup, StkId base,
                          StkId ra) {
@@ -645,11 +643,11 @@ static void pushclosure (lua_State *L, Proto *p, UpVal **encup, StkId base,
       ncl->upvals[i] = encup[uv[i].idx];
     /* new closure is white, so we do not need a barrier here */
   }
-  if (p->cachemiss >= 10)  /* too many missings? */
+  if (p->cachemiss >= MAXMISS)  /* too many missings? */
     p->cache = NULL;  /* give up cache */
   else {
-    if (!isblack(p))  /* cache will not break GC invariant? */
-      p->cache = ncl;  /* save it on cache for reuse */
+    p->cache = ncl;  /* save it on cache for reuse */
+    luaC_protobarrier(L, p, ncl);
     p->cachemiss++;
   }
 }