Don't try to lock the objhead mutex if we don't have an objhead. Doing so

caused the Varnish child to die immediately after sending its 503 response
if the backend didn't respond.

Reviewed by:	phk


git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1376 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_hash.c

@@ -185,6 +185,7 @@ HSH_Lookup(struct sess *sp)
 void
 HSH_Unbusy(struct object *o)
 {
+	struct objhead *oh;
 	struct sess *sp;
 
 	CHECK_OBJ_NOTNULL(o, OBJECT_MAGIC);
@@ -192,9 +193,14 @@ HSH_Unbusy(struct object *o)
 	assert(o->refcnt > 0);
 	if (o->cacheable)
 		EXP_Insert(o);
-	LOCK(&o->objhead->mtx);
+	oh = o->objhead;
+	if (oh != NULL) {
+		CHECK_OBJ(oh, OBJHEAD_MAGIC);
+		LOCK(&oh->mtx);
+	}
 	o->busy = 0;
-	UNLOCK(&o->objhead->mtx);
+	if (oh != NULL)
+		UNLOCK(&oh->mtx);
 	while (1) {
 		sp = TAILQ_FIRST(&o->waitinglist);
 		if (sp == NULL)