selftests/xsk: do not change XDP program when not necessary

Do not change the XDP program for the Tx thread when not needed. It
was erroneously compared to the XDP program for the Rx thread, which
is always going to be different, which meant that the code made
unnecessary switches to the same program it had before. This did not
affect functionality, just performance.
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/r/20230516103109.3066-2-magnus.karlsson@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/xskxceiver.c

@@ -1402,11 +1402,20 @@ static void handler(int signum)
 	pthread_exit(NULL);
 }
 
-static bool xdp_prog_changed(struct test_spec *test, struct ifobject *ifobj)
+static bool xdp_prog_changed_rx(struct test_spec *test)
 {
+	struct ifobject *ifobj = test->ifobj_rx;
+
 	return ifobj->xdp_prog != test->xdp_prog_rx || ifobj->mode != test->mode;
 }
 
+static bool xdp_prog_changed_tx(struct test_spec *test)
+{
+	struct ifobject *ifobj = test->ifobj_tx;
+
+	return ifobj->xdp_prog != test->xdp_prog_tx || ifobj->mode != test->mode;
+}
+
 static void xsk_reattach_xdp(struct ifobject *ifobj, struct bpf_program *xdp_prog,
 			     struct bpf_map *xskmap, enum test_mode mode)
 {
@@ -1433,13 +1442,13 @@ static void xsk_reattach_xdp(struct ifobject *ifobj, struct bpf_program *xdp_pro
 static void xsk_attach_xdp_progs(struct test_spec *test, struct ifobject *ifobj_rx,
 				 struct ifobject *ifobj_tx)
 {
-	if (xdp_prog_changed(test, ifobj_rx))
+	if (xdp_prog_changed_rx(test))
 		xsk_reattach_xdp(ifobj_rx, test->xdp_prog_rx, test->xskmap_rx, test->mode);
 
 	if (!ifobj_tx || ifobj_tx->shared_umem)
 		return;
 
-	if (xdp_prog_changed(test, ifobj_tx))
+	if (xdp_prog_changed_tx(test))
 		xsk_reattach_xdp(ifobj_tx, test->xdp_prog_tx, test->xskmap_tx, test->mode);
 }