[PATCH v11 14/14] kunit: add tests for smp_cond_load_relaxed_timeout()

[Ankur Arora]

Add a success and failure case for smp_cond_load_relaxed_timeout().

Both test cases wait on some state in smp_cond_load_relaxed_timeout().
In the success case we spawn a kthread that pokes the bit.

Signed-off-by: Ankur Arora <ankur.a.arora at oracle.com>
---
 lib/Kconfig.debug                |  10 +++
 lib/tests/Makefile               |   1 +
 lib/tests/barrier-timeout-test.c | 125 +++++++++++++++++++++++++++++++
 3 files changed, 136 insertions(+)
 create mode 100644 lib/tests/barrier-timeout-test.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 93f356d2b3d9..dcd2d60a9391 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2398,6 +2398,16 @@ config FPROBE_SANITY_TEST
 
 	  Say N if you are unsure.
 
+config BARRIER_TIMEOUT_TEST
+	tristate "KUnit tests for smp_cond_load_relaxed_timeout()"
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Builds KUnit tests that validate wake-up and timeout handling paths
+	  in smp_cond_load_relaxed_timeout().
+
+	  Say N if you are unsure.
+
 config BACKTRACE_SELF_TEST
 	tristate "Self test for the backtrace code"
 	depends on DEBUG_KERNEL
diff --git a/lib/tests/Makefile b/lib/tests/Makefile
index 05f74edbc62b..3504d677b7b8 100644
--- a/lib/tests/Makefile
+++ b/lib/tests/Makefile
@@ -20,6 +20,7 @@ CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN)
 obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o
 CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE)
 obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o
+obj-$(CONFIG_BARRIER_TIMEOUT_TEST) += barrier-timeout-test.o
 obj-$(CONFIG_GLOB_KUNIT_TEST) += glob_kunit.o
 obj-$(CONFIG_HASHTABLE_KUNIT_TEST) += hashtable_test.o
 obj-$(CONFIG_HASH_KUNIT_TEST) += test_hash.o
diff --git a/lib/tests/barrier-timeout-test.c b/lib/tests/barrier-timeout-test.c
new file mode 100644
index 000000000000..d72200daa0f2
--- /dev/null
+++ b/lib/tests/barrier-timeout-test.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests exercising smp_cond_load_relaxed_timeout().
+ *
+ * Copyright (c) 2026, Oracle Corp.
+ * Author: Ankur Arora <ankur.a.arora at oracle.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/types.h>
+#include <linux/sched/clock.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <asm/barrier.h>
+#include <kunit/test.h>
+#include <kunit/visibility.h>
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+struct clock_state {
+	s64 start_time;
+	s64 end_time;
+};
+
+#define TIMEOUT_MSEC	2
+#define TEST_FLAG_VAL	BIT(2)
+static unsigned int flag;
+
+static s64 basic_clock(struct clock_state *clk)
+{
+	clk->end_time = local_clock();
+	return clk->end_time;
+}
+
+static void update_flags(void)
+{
+	WRITE_ONCE(flag, TEST_FLAG_VAL);
+}
+
+static s64 mock_clock(struct clock_state *clk)
+{
+	s64 clk_mid = clk->start_time + (TIMEOUT_MSEC * NSEC_PER_MSEC)/2;
+
+	clk->end_time = local_clock();
+	if (clk->end_time >= clk_mid)
+		update_flags();
+	return clk->end_time;
+}
+
+typedef s64 (*clkfn_t)(struct clock_state *);
+
+static void test_smp_cond_relaxed_timeout(struct kunit *test,
+					  clkfn_t clock, bool succeeds)
+{
+	struct clock_state clk = {
+		.start_time = local_clock(),
+		.end_time = local_clock(),
+	};
+	s64 runtime, timeout_ns = TIMEOUT_MSEC * NSEC_PER_MSEC;
+	unsigned int result;
+
+	result = smp_cond_load_relaxed_timeout(&flag,
+					       (VAL & TEST_FLAG_VAL),
+					       clock(&clk),
+					       timeout_ns);
+
+	runtime = clk.end_time - clk.start_time;
+	KUNIT_EXPECT_EQ(test, (bool)(result & TEST_FLAG_VAL), succeeds);
+	KUNIT_EXPECT_EQ(test, runtime <= timeout_ns, succeeds);
+}
+
+static int smp_cond_threadfn(void *data)
+{
+	udelay(TIMEOUT_MSEC * USEC_PER_MSEC / 4);
+
+	/*
+	 * Update flags after a delay to give smp_cond_relaxed_timeout()
+	 * time to get started.
+	 */
+	update_flags();
+	return 0;
+}
+
+static void smp_cond_relaxed_timeout_succeeds(struct kunit *test)
+{
+	struct task_struct *task;
+
+	flag = 0;
+
+	task = kthread_run(smp_cond_threadfn, &flag, "smp_cond_thread");
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, task);
+	test_smp_cond_relaxed_timeout(test, &basic_clock, true);
+
+	kthread_stop(task);
+}
+
+static void smp_cond_relaxed_timeout_mocked(struct kunit *test)
+{
+	flag = 0;
+	test_smp_cond_relaxed_timeout(test, &mock_clock, true);
+}
+
+static void smp_cond_relaxed_timeout_expires(struct kunit *test)
+{
+	flag = 0;
+	test_smp_cond_relaxed_timeout(test, &basic_clock, false);
+}
+
+static struct kunit_case barrier_timeout_test_cases[] = {
+	KUNIT_CASE(smp_cond_relaxed_timeout_mocked),
+	KUNIT_CASE(smp_cond_relaxed_timeout_succeeds),
+	KUNIT_CASE(smp_cond_relaxed_timeout_expires),
+	{}
+};
+
+static struct kunit_suite barrier_timeout_test_suite = {
+	.name = "smp-cond-load-relaxed-timeout",
+	.test_cases = barrier_timeout_test_cases,
+};
+
+kunit_test_suite(barrier_timeout_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for smp_cond_load_relaxed_timeout()");
+MODULE_LICENSE("GPL");
-- 
2.31.1