From 988357628c2c84e891f5992c4f5cfb31fb3bd27b Mon Sep 17 00:00:00 2001 From: Tzung-Bi Shih Date: Thu, 29 Jan 2026 14:37:33 +0000 Subject: [PATCH] revocable: Add KUnit test for concurrent access Add a test case to verify correct synchronization between concurrent readers and a revocation. The test setup involves: 1. Consumer 1 enters the critical section (SRCU read lock) and verifies access to the resource. 2. Provider attempts to revoke the resource. This should block until Consumer 1 releases the lock. 3. Consumer 2 attempts to enter the critical section while revocation is pending. It should see the resource as revoked (NULL). 4. Consumer 1 exits, allowing the revocation to complete. This ensures that the SRCU mechanism correctly enforces grace periods and that new readers are properly prevented from accessing the resource once revocation has begun. A way to run the test: $ ./tools/testing/kunit/kunit.py run \ --kconfig_add CONFIG_REVOCABLE_KUNIT_TEST=y \ --kconfig_add CONFIG_PROVE_LOCKING=y \ --kconfig_add CONFIG_DEBUG_KERNEL=y \ --kconfig_add CONFIG_DEBUG_INFO=y \ --kconfig_add CONFIG_DEBUG_INFO_DWARF5=y \ --kconfig_add CONFIG_KASAN=y \ --kconfig_add CONFIG_DETECT_HUNG_TASK=y \ --kconfig_add CONFIG_DEFAULT_HUNG_TASK_TIMEOUT="10" \ --arch=x86_64 --raw_output=all \ revocable_test Signed-off-by: Tzung-Bi Shih Link: https://patch.msgid.link/20260129143733.45618-5-tzungbi@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/base/revocable_test.c | 104 ++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) diff --git a/drivers/base/revocable_test.c b/drivers/base/revocable_test.c index a2818ec01298..27f5d7d96f4b 100644 --- a/drivers/base/revocable_test.c +++ b/drivers/base/revocable_test.c @@ -17,9 +17,14 @@ * * - Provider Use-after-free: Verifies revocable_init() correctly handles * race conditions where the provider is being released. + * + * - Concurrent Access: Verifies multiple threads can access the resource. */ #include +#include +#include +#include #include #include @@ -160,12 +165,111 @@ static void revocable_test_provider_use_after_free(struct kunit *test) KUNIT_EXPECT_NE(test, ret, 0); } +struct test_concurrent_access_context { + struct kunit *test; + struct revocable_provider __rcu *rp; + struct revocable rev; + struct completion started, enter, exit; + struct task_struct *thread; + void *expected_res; +}; + +static int test_concurrent_access_provider(void *data) +{ + struct test_concurrent_access_context *ctx = data; + + complete(&ctx->started); + + wait_for_completion(&ctx->enter); + revocable_provider_revoke(&ctx->rp); + KUNIT_EXPECT_PTR_EQ(ctx->test, unrcu_pointer(ctx->rp), NULL); + + return 0; +} + +static int test_concurrent_access_consumer(void *data) +{ + struct test_concurrent_access_context *ctx = data; + void *res; + + complete(&ctx->started); + + wait_for_completion(&ctx->enter); + res = revocable_try_access(&ctx->rev); + KUNIT_EXPECT_PTR_EQ(ctx->test, res, ctx->expected_res); + + wait_for_completion(&ctx->exit); + revocable_withdraw_access(&ctx->rev); + + return 0; +} + +static void revocable_test_concurrent_access(struct kunit *test) +{ + struct revocable_provider __rcu *rp; + void *real_res = (void *)0x12345678; + struct test_concurrent_access_context *ctx; + int ret, i; + + rp = revocable_provider_alloc(real_res); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp); + + ctx = kunit_kmalloc_array(test, 3, sizeof(*ctx), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, ctx); + + for (i = 0; i < 3; ++i) { + ctx[i].test = test; + init_completion(&ctx[i].started); + init_completion(&ctx[i].enter); + init_completion(&ctx[i].exit); + + if (i == 0) { + ctx[i].rp = rp; + ctx[i].thread = kthread_run( + test_concurrent_access_provider, ctx + i, + "revocable_provider_%d", i); + } else { + ret = revocable_init(rp, &ctx[i].rev); + KUNIT_ASSERT_EQ(test, ret, 0); + + ctx[i].thread = kthread_run( + test_concurrent_access_consumer, ctx + i, + "revocable_consumer_%d", i); + } + KUNIT_ASSERT_FALSE(test, IS_ERR(ctx[i].thread)); + + wait_for_completion(&ctx[i].started); + } + ctx[1].expected_res = real_res; + ctx[2].expected_res = NULL; + + /* consumer1 enters read-side critical section */ + complete(&ctx[1].enter); + msleep(100); + /* provider0 revokes the resource */ + complete(&ctx[0].enter); + msleep(100); + /* consumer2 enters read-side critical section */ + complete(&ctx[2].enter); + msleep(100); + + /* consumer{1,2} exit read-side critical section */ + complete(&ctx[1].exit); + complete(&ctx[2].exit); + + for (i = 0; i < 3; ++i) + kthread_stop(ctx[i].thread); + for (i = 1; i < 3; ++i) + revocable_deinit(&ctx[i].rev); +} + static struct kunit_case revocable_test_cases[] = { KUNIT_CASE(revocable_test_basic), KUNIT_CASE(revocable_test_revocation), KUNIT_CASE(revocable_test_try_access_macro), KUNIT_CASE(revocable_test_try_access_macro2), KUNIT_CASE(revocable_test_provider_use_after_free), + KUNIT_CASE(revocable_test_concurrent_access), {} }; -- 2.47.3