Give node_subreq a pointer to the lock used with the condition variable

mostly to have it available in tree_free / tree_prune later

src/node.c

@@ -715,12 +715,12 @@ push_subreq(struct req *req, struct bytes_tree *tree,
 	(void) next;
 
 	if (node->subreq.done == 0) {
-		Lck_Lock(&tree->tree_lock);
+		Lck_Lock(node->subreq.shared_lock);
 		if (node->subreq.done == 0)
 			AZ(Lck_CondWait(
 				   &node->subreq.cond,
-				   &tree->tree_lock));
-		Lck_Unlock(&tree->tree_lock);
+				   node->subreq.shared_lock));
+		Lck_Unlock(node->subreq.shared_lock);
 	}
 
 	subreq = subreq_fixup(node, req);

src/node.h

@@ -154,9 +154,10 @@ struct node_subreq {
 	struct boc		*boc;
 	// oc is NULL if already transferred back into req
 	struct objcore		*oc;
+	struct lock		*shared_lock;	// == &tree->tree_lock
+	pthread_cond_t		cond;
 	// subreq to topreq delivery
 	int			done;
-	pthread_cond_t		cond;
 };
 
 // sub-state for node_final while in ST_DATA

src/vdp_pesi.c

@@ -1456,8 +1456,11 @@ vped_deliver(struct req *req, struct boc *boc, int wantbody)
 	HSH_Ref(req->objcore);
 	node->subreq.oc = req->objcore;
 
+	node->subreq.shared_lock = &tree->tree_lock;
 	AZ(pthread_cond_init(&node->subreq.cond, NULL));
 
+	AZ(node->subreq.done);
+
 	node_mutate_lock(tree, node, T_SUBREQ, ST_DATA);
 	node_mutate_unlock(tree);