scx: Add selftests for validating hotplug seq checks

Now that we have full hotplug sequence number support, as well as the
necessary macros in compat.h, let's extend the hotplug selftest to also
validate that the sequence number can be used to detect hotplug events.

Signed-off-by: David Vernet <[email protected]>

tools/testing/selftests/sched_ext/hotplug.c

@@ -15,8 +15,6 @@
 #include "scx_test.h"
 #include "util.h"
 
-struct hotplug *skel;
-
 const char *online_path = "/sys/devices/system/cpu/cpu1/online";
 
 static bool is_cpu_online(void)
@@ -40,22 +38,20 @@ static enum scx_test_status setup(void **ctx)
 	if (!is_cpu_online())
 		return SCX_TEST_SKIP;
 
-	skel = hotplug__open_and_load();
-	if (!skel) {
-		SCX_ERR("Failed to open and load hotplug skel");
-		return SCX_TEST_FAIL;
-	}
-
 	return SCX_TEST_PASS;
 }
 
 static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined)
 {
+	struct hotplug *skel;
 	struct bpf_link *link;
 	long kind, code;
 
 	SCX_ASSERT(is_cpu_online());
 
+	skel = hotplug__open_and_load();
+	SCX_ASSERT(skel);
+
 	/* Testing the offline -> online path, so go offline before starting */
 	if (onlining)
 		toggle_online_status(0);
@@ -78,6 +74,7 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined)
 
 	if (!link) {
 		SCX_ERR("Failed to attach scheduler");
+		hotplug__destroy(skel);
 		return SCX_TEST_FAIL;
 	}
 
@@ -93,12 +90,51 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined)
 		toggle_online_status(1);
 
 	bpf_link__destroy(link);
-
-	UEI_RESET(skel, uei);
+	hotplug__destroy(skel);
 
 	return SCX_TEST_PASS;
 }
 
+static enum scx_test_status test_hotplug_attach(void)
+{
+	struct hotplug *skel;
+	struct bpf_link *link;
+	enum scx_test_status status = SCX_TEST_PASS;
+	long kind, code;
+
+	SCX_ASSERT(is_cpu_online());
+	SCX_ASSERT(scx_hotplug_seq() > 0);
+
+	skel = SCX_OPS_OPEN(hotplug_nocb_ops, hotplug);
+	SCX_ASSERT(skel);
+
+	SCX_OPS_LOAD(skel, hotplug_nocb_ops, hotplug, uei);
+
+	/*
+	 * Take the CPU offline to increment the global hotplug seq, which
+	 * should cause attach to fail due to us setting the hotplug seq above
+	 */
+	toggle_online_status(0);
+	link = bpf_map__attach_struct_ops(skel->maps.hotplug_nocb_ops);
+
+	toggle_online_status(1);
+
+	SCX_ASSERT(link);
+	while (!UEI_EXITED(skel, uei))
+		sched_yield();
+
+	kind = SCX_KIND_VAL(SCX_EXIT_UNREG_KERN);
+	code = SCX_ECODE_VAL(SCX_ECODE_ACT_RESTART) |
+	       SCX_ECODE_VAL(SCX_ECODE_RSN_HOTPLUG);
+	SCX_EQ(UEI_KIND(skel, uei), kind);
+	SCX_EQ(UEI_ECODE(skel, uei), code);
+
+	bpf_link__destroy(link);
+	hotplug__destroy(skel);
+
+	return status;
+}
+
 static enum scx_test_status run(void *ctx)
 {
 
@@ -114,12 +150,11 @@ static enum scx_test_status run(void *ctx)
 
 #undef HP_TEST
 
-	return SCX_TEST_PASS;
+	return test_hotplug_attach();
 }
 
 static void cleanup(void *ctx)
 {
-	hotplug__destroy(skel);
 	toggle_online_status(1);
 }