[PATCH 8/8] lib/tests/slub_kunit: add a test case for kfree_rcu_nolock()

Harry Yoo (Oracle)
2026-04-16T09:10:57Z

Similar to test_kmalloc_kfree_nolock, add a test that allocates objects
via kmalloc_nolock() and frees them via kfree_rcu_nolock() in a perf
overflow handler (NMI or hardirq depending on the arch), while the main
loop allocates and frees objects via kmalloc() and kfree_rcu().

Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org>
---
lib/tests/slub_kunit.c | 73 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 73 insertions(+)

diff --git a/lib/tests/slub_kunit.c b/lib/tests/slub_kunit.c
index fa6d31dbca16..f8d979912246 100644
--- a/lib/tests/slub_kunit.c
+++ b/lib/tests/slub_kunit.c
@@ -367,6 +367,78 @@ static void test_kmalloc_kfree_nolock(struct kunit *test)
kfree(objects[j]);
}

+cleanup:
+ perf_event_disable(ctx.event);
+ perf_event_release_kernel(ctx.event);
+
+ kunit_info(test, "callback_count: %d, alloc_ok: %d, alloc_fail: %d\n",
+ ctx.callback_count, ctx.alloc_ok, ctx.alloc_fail);
+
+ if (alloc_fail)
+ kunit_skip(test, "Allocation failed");
+ KUNIT_EXPECT_EQ(test, 0, slab_errors);
+}
+
+struct dummy_struct {
+ struct rcu_ptr rcu;
+};
+
+static void overflow_handler_test_kfree_rcu_nolock(struct perf_event *event,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
+{
+ struct dummy_struct *dummy;
+ gfp_t gfp;
+ struct test_nolock_context *ctx = event->overflow_handler_context;
+
+ /* __GFP_ACCOUNT to test kmalloc_nolock() in alloc_slab_obj_exts() */
+ gfp = (ctx->callback_count % 2) ? 0 : __GFP_ACCOUNT;
+ dummy = kmalloc_nolock(sizeof(*dummy), gfp, NUMA_NO_NODE);
+
+ if (dummy) {
+ ctx->alloc_ok++;
+ kfree_rcu_nolock(dummy, rcu);
+ } else {
+ ctx->alloc_fail++;
+ }
+ ctx->callback_count++;
+}
+
+static void test_kfree_rcu_nolock(struct kunit *test)
+{
+ int i, j;
+ struct test_nolock_context ctx = { .test = test };
+ struct perf_event *event;
+ bool alloc_fail = false;
+ struct dummy_struct *dummy;
+
+ if (IS_BUILTIN(CONFIG_SLUB_KUNIT_TEST))
+ kunit_skip(test, "can't do kfree_rcu_nolock() when test is built-in");
+
+ event = perf_event_create_kernel_counter(&hw_attr, -1, current,
+ overflow_handler_test_kfree_rcu_nolock,
+ &ctx);
+ if (IS_ERR(event))
+ kunit_skip(test, "Failed to create perf event");
+ ctx.event = event;
+ perf_event_enable(ctx.event);
+ for (i = 0; i < NR_ITERATIONS; i++) {
+ for (j = 0; j < NR_OBJECTS; j++) {
+ gfp_t gfp = (i % 2) ? GFP_KERNEL : GFP_KERNEL_ACCOUNT;
+
+ objects[j] = kmalloc(sizeof(*dummy), gfp);
+ if (!objects[j]) {
+ j--;
+ while (j >= 0)
+ kfree(objects[j--]);
+ alloc_fail = true;
+ goto cleanup;
+ }
+ }
+ for (j = 0; j < NR_OBJECTS; j++)
+ kfree_rcu((struct dummy_struct *)objects[j], rcu);
+ }
+
cleanup:
perf_event_disable(ctx.event);
perf_event_release_kernel(ctx.event);
@@ -406,6 +478,7 @@ static struct kunit_case test_cases[] = {
KUNIT_CASE(test_krealloc_redzone_zeroing),
#ifdef CONFIG_PERF_EVENTS
KUNIT_CASE_SLOW(test_kmalloc_kfree_nolock),
+ KUNIT_CASE_SLOW(test_kfree_rcu_nolock),
#endif
{}
};
--
2.43.0