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_RATELIMIT_KUNIT_TEST=y --kconfig_add CONFIG_SMP=y lib_ratelimit

This will fail on old ___ratelimit(), and subsequent patches provide
the fixes that are required.

[ paulmck:  Apply timeout and kunit feedback from Petr Mladek. ]

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.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/tests/Makefile         |  1 +
 lib/tests/test_ratelimit.c | 79 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 lib/tests/test_ratelimit.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ebe33181b6e6e..d69d27f808340 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -3225,6 +3225,17 @@ config TEST_OBJPOOL
 
 	  If unsure, say N.
 
+config RATELIMIT_KUNIT_TEST
+	tristate "KUnit Test 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/tests/Makefile b/lib/tests/Makefile
index 56d6450144828..3edc30a515840 100644
--- a/lib/tests/Makefile
+++ b/lib/tests/Makefile
@@ -46,5 +46,6 @@ obj-$(CONFIG_STRING_KUNIT_TEST) += string_kunit.o
 obj-$(CONFIG_STRING_HELPERS_KUNIT_TEST) += string_helpers_kunit.o
 obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o
 obj-$(CONFIG_UTIL_MACROS_KUNIT) += util_macros_kunit.o
+obj-$(CONFIG_RATELIMIT_KUNIT_TEST) += test_ratelimit.o
 
 obj-$(CONFIG_TEST_RUNTIME_MODULE)		+= module/
diff --git a/lib/tests/test_ratelimit.c b/lib/tests/test_ratelimit.c
new file mode 100644
index 0000000000000..0374107f5ea89
--- /dev/null
+++ b/lib/tests/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_SLOW(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

On Wed,  9 Jul 2025 11:03:33 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:

> 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_RATELIMIT_KUNIT_TEST=y --kconfig_add CONFIG_SMP=y lib_ratelimit
> 
> This will fail on old ___ratelimit(), and subsequent patches provide
> the fixes that are required.
> 
> [ paulmck:  Apply timeout and kunit feedback from Petr Mladek. ]

The above line makes me suspect that this was paulmck tweaking someone
else's patch.  If the authorship correct on this one?

On Wed, 9 Jul 2025 15:41:52 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed,  9 Jul 2025 11:03:33 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> 
> > 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_RATELIMIT_KUNIT_TEST=y --kconfig_add CONFIG_SMP=y lib_ratelimit
> > 
> > This will fail on old ___ratelimit(), and subsequent patches provide
> > the fixes that are required.
> > 
> > [ paulmck:  Apply timeout and kunit feedback from Petr Mladek. ]  
> 
> The above line makes me suspect that this was paulmck tweaking someone
> else's patch.  If the authorship correct on this one?

Looks to me that Paul just took some advice from Petr and was just giving
credit. Perhaps he could lose the "paulmck:" part?

Perhaps:

  Suggested-by: Petr Mladek <pmladek@suse.com> # for timeout and kunit feedback

?

-- Steve

On Wed, Jul 09, 2025 at 06:46:29PM -0400, Steven Rostedt wrote:
> On Wed, 9 Jul 2025 15:41:52 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Wed,  9 Jul 2025 11:03:33 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > 
> > > 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_RATELIMIT_KUNIT_TEST=y --kconfig_add CONFIG_SMP=y lib_ratelimit
> > > 
> > > This will fail on old ___ratelimit(), and subsequent patches provide
> > > the fixes that are required.
> > > 
> > > [ paulmck:  Apply timeout and kunit feedback from Petr Mladek. ]  
> > 
> > The above line makes me suspect that this was paulmck tweaking someone
> > else's patch.  If the authorship correct on this one?
> 
> Looks to me that Paul just took some advice from Petr and was just giving
> credit. Perhaps he could lose the "paulmck:" part?

You got it!

> Perhaps:
> 
>   Suggested-by: Petr Mladek <pmladek@suse.com> # for timeout and kunit feedback

That would work for me.

							Thanx, Paul