[master] c1aa3c20b Proper locking around n_backend. Found by Coverity.

[Poul-Henning Kamp]

commit c1aa3c20b4377e1eedb545fdf15edd60c4b72c9a
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Mon Dec 11 13:45:34 2023 +0000

    Proper locking around n_backend.  Found by Coverity.

diff --git a/vmod/vmod_directors.c b/vmod/vmod_directors.c
index 2334e0c14..44b98217f 100644
--- a/vmod/vmod_directors.c
+++ b/vmod/vmod_directors.c
@@ -94,9 +94,11 @@ vdir_release(struct vdir *vd)
 
 	CHECK_OBJ_NOTNULL(vd, VDIR_MAGIC);
 
+	vdir_wrlock(vd);
 	for (u = 0; u < vd->n_backend; u++)
 		VRT_Assign_Backend(&vd->backend[u], NULL);
 	vd->n_backend = 0;
+	vdir_unlock(vd);
 }
 
 void
diff --git a/vmod/vmod_directors_round_robin.c b/vmod/vmod_directors_round_robin.c
index 015e060da..f2ee59f04 100644
--- a/vmod/vmod_directors_round_robin.c
+++ b/vmod/vmod_directors_round_robin.c
@@ -90,9 +90,9 @@ vmod_rr_resolve(VRT_CTX, VCL_BACKEND dir)
 			break;
 	}
 	rr->nxt = nxt;
-	vdir_unlock(rr->vd);
 	if (u == rr->vd->n_backend)
 		be = NULL;
+	vdir_unlock(rr->vd);
 	return (be);
 }