[PATCH v2 ratelimit 01/14] lib: Add trivial kunit test for ratelimit

["Paul E. McKenney" <paulmck@kernel.org>]

Add a simple single-threaded smoke test for lib/ratelimit.c

To run on x86:

	make ARCH=x86_64 mrproper
	./tools/testing/kunit/kunit.py run --arch x86_64 --kconfig_add CONFIG_TEST_RATELIMIT=y --kconfig_add CONFIG_SMP=y lib_ratelimit

[ paulmck:  Apply timeout feedback from Petr Mladek. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Jon Pan-Doh <pandoh@google.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Karolina Stolarek <karolina.stolarek@oracle.com>
---
 lib/Kconfig.debug    | 11 ++++++
 lib/Makefile         |  1 +
 lib/test_ratelimit.c | 79 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 lib/test_ratelimit.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9fe4d8dfe5782..581d6a8489670 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -3232,6 +3232,17 @@ config TEST_OBJPOOL
 
 	  If unsure, say N.
 
+config TEST_RATELIMIT
+	tristate "Test module for correctness and stress of ratelimit" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the "test_ratelimit" module that should be used
+	  for correctness verification and concurrent testings of rate
+	  limiting.
+
+	  If unsure, say N.
+
 config INT_POW_KUNIT_TEST
 	tristate "Integer exponentiation (int_pow) test" if !KUNIT_ALL_TESTS
 	depends on KUNIT
diff --git a/lib/Makefile b/lib/Makefile
index f07b24ce1b3f8..9d1f15c91929a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -103,6 +103,7 @@ obj-$(CONFIG_TEST_HMM) += test_hmm.o
 obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
 obj-$(CONFIG_TEST_REF_TRACKER) += test_ref_tracker.o
 obj-$(CONFIG_TEST_OBJPOOL) += test_objpool.o
+obj-$(CONFIG_TEST_RATELIMIT) += test_ratelimit.o
 
 obj-$(CONFIG_TEST_FPU) += test_fpu.o
 test_fpu-y := test_fpu_glue.o test_fpu_impl.o
diff --git a/lib/test_ratelimit.c b/lib/test_ratelimit.c
new file mode 100644
index 0000000000000..45b673bbab9e4
--- /dev/null
+++ b/lib/test_ratelimit.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <kunit/test.h>
+
+#include <linux/ratelimit.h>
+#include <linux/module.h>
+
+/* a simple boot-time regression test */
+
+#define TESTRL_INTERVAL (5 * HZ)
+static DEFINE_RATELIMIT_STATE(testrl, TESTRL_INTERVAL, 3);
+
+#define test_ratelimited(test, expected) \
+	KUNIT_ASSERT_EQ(test, ___ratelimit(&testrl, "test_ratelimit_smoke"), (expected));
+
+static void test_ratelimit_smoke(struct kunit *test)
+{
+	// Check settings.
+	KUNIT_ASSERT_GE(test, TESTRL_INTERVAL, 100);
+
+	// Test normal operation.
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, false);
+
+	schedule_timeout_idle(TESTRL_INTERVAL - 40);
+	test_ratelimited(test, false);
+
+	schedule_timeout_idle(50);
+	test_ratelimited(test, true);
+
+	schedule_timeout_idle(2 * TESTRL_INTERVAL);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+
+	schedule_timeout_idle(TESTRL_INTERVAL - 40);
+	test_ratelimited(test, true);
+	schedule_timeout_idle(50);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, false);
+
+	// Test disabling.
+	testrl.burst = 0;
+	test_ratelimited(test, false);
+	testrl.burst = 2;
+	testrl.interval = 0;
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+
+	// Testing re-enabling.
+	testrl.interval = TESTRL_INTERVAL;
+	test_ratelimited(test, true);
+	test_ratelimited(test, true);
+	test_ratelimited(test, false);
+	test_ratelimited(test, false);
+}
+
+static struct kunit_case sort_test_cases[] = {
+	KUNIT_CASE(test_ratelimit_smoke),
+	{}
+};
+
+static struct kunit_suite ratelimit_test_suite = {
+	.name = "lib_ratelimit",
+	.test_cases = sort_test_cases,
+};
+
+kunit_test_suites(&ratelimit_test_suite);
+
+MODULE_DESCRIPTION("___ratelimit() KUnit test suite");
+MODULE_LICENSE("GPL");
-- 
2.40.1