Commit 98835762 authored by Tzung-Bi Shih's avatar Tzung-Bi Shih Committed by Greg Kroah-Hartman
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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: default avatarTzung-Bi Shih <tzungbi@kernel.org>
Link: https://patch.msgid.link/20260129143733.45618-5-tzungbi@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 377563ce

drivers/base/revocable_test.c

+104 −0
Original line number Diff line number Diff line
@@ -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 <kunit/test.h>

#include <linux/completion.h>

#include <linux/delay.h>

#include <linux/kthread.h>

#include <linux/refcount.h>

#include <linux/revocable.h>
@@ -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),

	{}

};