Many uses of the KUnit resource system are intended to simply defer calling a function until the test exits (be it due to success or failure). The existing kunit_alloc_resource() function is often used for this, but was awkward to use (requiring passing NULL init functions, etc), and returned a resource without incrementing its reference count, which -- while okay for this use-case -- could cause problems in others.

Instead, introduce a simple kunit_add_action() API: a simple function (returning nothing, accepting a single void* argument) can be scheduled to be called when the test exits. Deferred actions are called in the opposite order to that which they were registered.

This mimics the devres API, devm_add_action(), and also provides kunit_remove_action(), to cancel a deferred action, and kunit_release_action() to trigger one early.

This is implemented as a resource under the hood, so the ordering between resource cleanup and deferred functions is maintained.

Signed-off-by: David Gow davidgow@google.com ---

Note: there is a checkpatch warning: "function definition argument 'void *' should also have an identifier name"

I think this is a false-positive, as we're defining a function pointer struct member, not a specific function.

Changes since RFC v2: https://lore.kernel.org/linux-kselftest/20230331080411.981038-2-davidgow@goo... - Got rid of internal_gfp - everything uses GFP_KERNEL now - This includes kunit_kzalloc() and friends, which still allocate the returned memory with the provided GFP, but use GFP_KERNEL for internal bookkeeping data. - Thanks Maxime & Benjamin! - Got rid of cancellation tokens. - kunit_add_action() now returns 0 on success, otherwise an error - Note that this can quite easily lead to a memory leak, so look at kunit_add_action_or_reset() - Thanks Maxime & Benjamin! - Added kunit_add_action_or_reset - Matches devm_add_action_or_reset() - Returns 0 on success. - Thanks Maxime & Benjamin! - Got rid of the kunit_defer_func_t typedef. - I liked it, but it is probably pushing the boundaries of kernel style. - Use (void (*)(void *)) instead.

Changes since RFC v1: https://lore.kernel.org/linux-kselftest/20230325043104.3761770-2-davidgow@go... - Rename functions to better match the devm_* APIs. (Thanks Maxime) - Embed the kunit_resource in struct kunit_action_ctx to avoid an extra allocation (Thanks Benjamin) - Use 'struct kunit_action_ctx' as the type for cancellation tokens (Thanks Benjamin) - Add tests.

include/kunit/resource.h | 76 ++++++++++++++++++++++++++++++++ lib/kunit/kunit-test.c | 88 ++++++++++++++++++++++++++++++++++++- lib/kunit/resource.c | 95 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 258 insertions(+), 1 deletion(-)

diff --git a/include/kunit/resource.h b/include/kunit/resource.h index c0d88b318e90..6db28cd43e9b 100644 --- a/include/kunit/resource.h +++ b/include/kunit/resource.h @@ -387,4 +387,80 @@ static inline int kunit_destroy_named_resource(struct kunit *test, */ void kunit_remove_resource(struct kunit *test, struct kunit_resource *res);

+ +/** + * kunit_add_action() - Defer an 'action' (function call) until the test ends. + * @test: Test case to associate the action with. + * @func: The function to run on test exit + * @ctx: Data passed into @func + * + * Defer the execution of a function until the test exits, either normally or + * due to a failure. @ctx is passed as additional context. All functions + * registered with kunit_add_action() will execute in the opposite order to that + * they were registered in. + * + * This is useful for cleaning up allocated memory and resources. + * + * Returns: + * 0 on success, an error if the action could not be deferred. + */ +int kunit_add_action(struct kunit *test, void (*action) (void *), void *ctx); + +/** + * kunit_add_action_or_reset() - Defer an 'action' (function call) until the test ends. + * @test: Test case to associate the action with. + * @func: The function to run on test exit + * @ctx: Data passed into @func + * + * Defer the execution of a function until the test exits, either normally or + * due to a failure. @ctx is passed as additional context. All functions + * registered with kunit_add_action() will execute in the opposite order to that + * they were registered in. + * + * This is useful for cleaning up allocated memory and resources. + * + * If the action cannot be created (e.g., due to the system being out of memory), + * then action(ctx) will be called immediately, and an error will be returned. + * + * Returns: + * 0 on success, an error if the action could not be deferred. + */ +int kunit_add_action_or_reset(struct kunit *test, void (*action)(void *), + void *ctx); + +/** + * kunit_remove_action() - Cancel a matching deferred action. + * @test: Test case the action is associated with. + * @func: The deferred function to cancel. + * @ctx: The context passed to the deferred function to trigger. + * + * Prevent an action deferred via kunit_add_action() from executing when the + * test terminates.. + * If the function/context pair was deferred multiple times, only the most + * recent one will be cancelled. + */ +void kunit_remove_action(struct kunit *test, + void (*action)(void *), + void *ctx); + +/** + * kunit_release_action() - Run a matching action call immediately. + * @test: Test case the action is associated with. + * @func: The deferred function to trigger. + * @ctx: The context passed to the deferred function to trigger. + * + * Execute a function deferred via kunit_add_action()) immediately, rather than + * when the test ends. + * If the function/context pair was deferred multiple times, it will only be + * executed once here. The most recent deferral will no longer execute when + * the test ends. + * + * kunit_release_action(test, func, ctx); + * is equivalent to + * func(ctx); + * kunit_remove_action(test, func, ctx); + */ +void kunit_release_action(struct kunit *test, + void (*action)(void *), + void *ctx); #endif /* _KUNIT_RESOURCE_H */ diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c index 42e44caa1bdd..83d8e90ca7a2 100644 --- a/lib/kunit/kunit-test.c +++ b/lib/kunit/kunit-test.c @@ -112,7 +112,7 @@ struct kunit_test_resource_context { struct kunit test; bool is_resource_initialized; int allocate_order[2]; - int free_order[2]; + int free_order[4]; };

static int fake_resource_init(struct kunit_resource *res, void *context) @@ -403,6 +403,88 @@ static void kunit_resource_test_named(struct kunit *test) KUNIT_EXPECT_TRUE(test, list_empty(&test->resources)); }

+static void increment_int(void *ctx) +{ + int *i = (int *)ctx; + (*i)++; +} + +static void kunit_resource_test_action(struct kunit *test) +{ + int num_actions = 0; + + kunit_add_action(test, increment_int, &num_actions); + KUNIT_EXPECT_EQ(test, num_actions, 0); + kunit_cleanup(test); + KUNIT_EXPECT_EQ(test, num_actions, 1); + + /* Once we've cleaned up, the action queue is empty. */ + kunit_cleanup(test); + KUNIT_EXPECT_EQ(test, num_actions, 1); + + /* Check the same function can be deferred multiple times. */ + kunit_add_action(test, increment_int, &num_actions); + kunit_add_action(test, increment_int, &num_actions); + kunit_cleanup(test); + KUNIT_EXPECT_EQ(test, num_actions, 3); +} +static void kunit_resource_test_remove_action(struct kunit *test) +{ + int num_actions = 0; + + kunit_add_action(test, increment_int, &num_actions); + KUNIT_EXPECT_EQ(test, num_actions, 0); + + kunit_remove_action(test, increment_int, &num_actions); + kunit_cleanup(test); + KUNIT_EXPECT_EQ(test, num_actions, 0); +} +static void kunit_resource_test_release_action(struct kunit *test) +{ + int num_actions = 0; + + kunit_add_action(test, increment_int, &num_actions); + KUNIT_EXPECT_EQ(test, num_actions, 0); + /* Runs immediately on trigger. */ + kunit_release_action(test, increment_int, &num_actions); + KUNIT_EXPECT_EQ(test, num_actions, 1); + + /* Doesn't run again on test exit. */ + kunit_cleanup(test); + KUNIT_EXPECT_EQ(test, num_actions, 1); +} +static void action_order_1(void *ctx) +{ + struct kunit_test_resource_context *res_ctx = (struct kunit_test_resource_context *)ctx; + + KUNIT_RESOURCE_TEST_MARK_ORDER(res_ctx, free_order, 1); + kunit_log(KERN_INFO, current->kunit_test, "action_order_1"); +} +static void action_order_2(void *ctx) +{ + struct kunit_test_resource_context *res_ctx = (struct kunit_test_resource_context *)ctx; + + KUNIT_RESOURCE_TEST_MARK_ORDER(res_ctx, free_order, 2); + kunit_log(KERN_INFO, current->kunit_test, "action_order_2"); +} +static void kunit_resource_test_action_ordering(struct kunit *test) +{ + struct kunit_test_resource_context *ctx = test->priv; + + kunit_add_action(test, action_order_1, ctx); + kunit_add_action(test, action_order_2, ctx); + kunit_add_action(test, action_order_1, ctx); + kunit_add_action(test, action_order_2, ctx); + kunit_remove_action(test, action_order_1, ctx); + kunit_release_action(test, action_order_2, ctx); + kunit_cleanup(test); + + /* [2 is triggered] [2], [(1 is cancelled)] [1] */ + KUNIT_EXPECT_EQ(test, ctx->free_order[0], 2); + KUNIT_EXPECT_EQ(test, ctx->free_order[1], 2); + KUNIT_EXPECT_EQ(test, ctx->free_order[2], 1); +} + static int kunit_resource_test_init(struct kunit *test) { struct kunit_test_resource_context *ctx = @@ -434,6 +516,10 @@ static struct kunit_case kunit_resource_test_cases[] = { KUNIT_CASE(kunit_resource_test_proper_free_ordering), KUNIT_CASE(kunit_resource_test_static), KUNIT_CASE(kunit_resource_test_named), + KUNIT_CASE(kunit_resource_test_action), + KUNIT_CASE(kunit_resource_test_remove_action), + KUNIT_CASE(kunit_resource_test_release_action), + KUNIT_CASE(kunit_resource_test_action_ordering), {} };

diff --git a/lib/kunit/resource.c b/lib/kunit/resource.c index c414df922f34..20b08b9341c9 100644 --- a/lib/kunit/resource.c +++ b/lib/kunit/resource.c @@ -77,3 +77,98 @@ int kunit_destroy_resource(struct kunit *test, kunit_resource_match_t match, return 0; } EXPORT_SYMBOL_GPL(kunit_destroy_resource); + +struct kunit_action_ctx { + struct kunit_resource res; + void (*func)(void *); + void *ctx; +}; + +static void __kunit_action_free(struct kunit_resource *res) +{ + struct kunit_action_ctx *action_ctx = container_of(res, struct kunit_action_ctx, res); + + action_ctx->func(action_ctx->ctx); +} + + +int kunit_add_action(struct kunit *test, void (*action)(void *), void *ctx) +{ + struct kunit_action_ctx *action_ctx; + + KUNIT_ASSERT_NOT_NULL_MSG(test, action, "Tried to action a NULL function!"); + + action_ctx = kzalloc(sizeof(*action_ctx), GFP_KERNEL); + if (!action_ctx) + return -ENOMEM; + + action_ctx->func = action; + action_ctx->ctx = ctx; + + action_ctx->res.should_kfree = true; + /* As init is NULL, this cannot fail. */ + __kunit_add_resource(test, NULL, __kunit_action_free, &action_ctx->res, action_ctx); + + return 0; +} + +int kunit_add_action_or_reset(struct kunit *test, void (*action)(void *), + void *ctx) +{ + int res = kunit_add_action(test, action, ctx); + + if (res) + action(ctx); + return res; +} + +static bool __kunit_action_match(struct kunit *test, + struct kunit_resource *res, void *match_data) +{ + struct kunit_action_ctx *match_ctx = (struct kunit_action_ctx *)match_data; + struct kunit_action_ctx *res_ctx = container_of(res, struct kunit_action_ctx, res); + + /* Make sure this is a free function. */ + if (res->free != __kunit_action_free) + return false; + + /* Both the function and context data should match. */ + return (match_ctx->func == res_ctx->func) && (match_ctx->ctx == res_ctx->ctx); +} + +void kunit_remove_action(struct kunit *test, + void (*action)(void *), + void *ctx) +{ + struct kunit_action_ctx match_ctx; + struct kunit_resource *res; + + match_ctx.func = action; + match_ctx.ctx = ctx; + + res = kunit_find_resource(test, __kunit_action_match, &match_ctx); + if (res) { + /* Remove the free function so we don't run the action. */ + res->free = NULL; + kunit_remove_resource(test, res); + kunit_put_resource(res); + } +} + +void kunit_release_action(struct kunit *test, + void (*action)(void *), + void *ctx) +{ + struct kunit_action_ctx match_ctx; + struct kunit_resource *res; + + match_ctx.func = action; + match_ctx.ctx = ctx; + + res = kunit_find_resource(test, __kunit_action_match, &match_ctx); + if (res) { + kunit_remove_resource(test, res); + /* We have to put() this here, else free won't be called. */ + kunit_put_resource(res); + } +}

The kunit_add_action() function is much simpler and cleaner to use that the full KUnit resource API for simple things like the kunit_kmalloc_array() functionality.

Replacing it allows us to get rid of a number of helper functions, and leaves us with no uses of kunit_alloc_resource(), which has some usability problems and is going to have its behaviour modified in an upcoming patch.

Note that we need to use kunit_release_action() to implement kunit_kfree().

Signed-off-by: David Gow davidgow@google.com ---

Changes since RFCv2: https://lore.kernel.org/linux-kselftest/20230331080411.981038-4-davidgow@goo... - Update to match changes in the the action API. - Always allocate the action context with GFP_KERNEL. - Update documentation to note that this will cause GFP_KERNEL allocations, regardless of the gfp argument passed in.

--- include/kunit/test.h | 10 +++++++-- lib/kunit/test.c | 48 +++++++++----------------------------------- 2 files changed, 17 insertions(+), 41 deletions(-)

diff --git a/include/kunit/test.h b/include/kunit/test.h index 57b309c6ca27..3e8e98d0d8b1 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -321,8 +321,11 @@ enum kunit_status kunit_suite_has_succeeded(struct kunit_suite *suite); * @gfp: flags passed to underlying kmalloc(). * * Just like `kmalloc_array(...)`, except the allocation is managed by the test case - * and is automatically cleaned up after the test case concludes. See &struct - * kunit_resource for more information. + * and is automatically cleaned up after the test case concludes. See kunit_add_action() + * for more information. + * + * Note that some internal context data is also allocated with GFP_KERNEL, + * regardless of the gfp passed in. */ void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp);

@@ -333,6 +336,9 @@ void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp); * @gfp: flags passed to underlying kmalloc(). * * See kmalloc() and kunit_kmalloc_array() for more information. + * + * Note that some internal context data is also allocated with GFP_KERNEL, + * regardless of the gfp passed in. */ static inline void *kunit_kmalloc(struct kunit *test, size_t size, gfp_t gfp) { diff --git a/lib/kunit/test.c b/lib/kunit/test.c index e2910b261112..6aafe2138766 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -712,58 +712,28 @@ static struct notifier_block kunit_mod_nb = { }; #endif

-struct kunit_kmalloc_array_params { - size_t n; - size_t size; - gfp_t gfp; -}; - -static int kunit_kmalloc_array_init(struct kunit_resource *res, void *context) +void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp) { - struct kunit_kmalloc_array_params *params = context; + void *data;

- res->data = kmalloc_array(params->n, params->size, params->gfp); - if (!res->data) - return -ENOMEM; + data = kmalloc_array(n, size, gfp);

- return 0; -} + if (!data) + return NULL;

-static void kunit_kmalloc_array_free(struct kunit_resource *res) -{ - kfree(res->data); -} + if (kunit_add_action_or_reset(test, (void (*)(void *))kfree, data) != 0) + return NULL;

-void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp) -{ - struct kunit_kmalloc_array_params params = { - .size = size, - .n = n, - .gfp = gfp - }; - - return kunit_alloc_resource(test, - kunit_kmalloc_array_init, - kunit_kmalloc_array_free, - gfp, - &params); + return data; } EXPORT_SYMBOL_GPL(kunit_kmalloc_array);

-static inline bool kunit_kfree_match(struct kunit *test, - struct kunit_resource *res, void *match_data) -{ - /* Only match resources allocated with kunit_kmalloc() and friends. */ - return res->free == kunit_kmalloc_array_free && res->data == match_data; -} - void kunit_kfree(struct kunit *test, const void *ptr) { if (!ptr) return;

- if (kunit_destroy_resource(test, kunit_kfree_match, (void *)ptr)) - KUNIT_FAIL(test, "kunit_kfree: %px already freed or not allocated by kunit", ptr); + kunit_release_action(test, (void (*)(void *))kfree, (void *)ptr); } EXPORT_SYMBOL_GPL(kunit_kfree);

On Fri, Apr 21, 2023 at 1:42 AM David Gow davidgow@google.com wrote:

Many uses of the KUnit resource system are intended to simply defer calling a function until the test exits (be it due to success or failure). The existing kunit_alloc_resource() function is often used for this, but was awkward to use (requiring passing NULL init functions, etc), and returned a resource without incrementing its reference count, which -- while okay for this use-case -- could cause problems in others.

Instead, introduce a simple kunit_add_action() API: a simple function (returning nothing, accepting a single void* argument) can be scheduled to be called when the test exits. Deferred actions are called in the opposite order to that which they were registered.

This mimics the devres API, devm_add_action(), and also provides kunit_remove_action(), to cancel a deferred action, and kunit_release_action() to trigger one early.

Apologies for the delayed bikeshedding.

I think mimicking the devres API is a better idea than kunit_defer() and friends. But I can't help but think this still isn't the best name. I personally would have no idea what `kunit_release_action()` does without looking it up.

I feel like `kunit_add_cleanup()` probably works better for a unit test framework. I think `kunit_remove_cleanup()` is fine and `kunit_release_cleanup()` is questionably ok. Instead of `release`, maybe it should be `kunit_trigger_cleanup()` or more verbosely, something like `kunit_early_trigger_cleanup()`.

I tried to look for equivalents in other languages/frameworks: * Rust and C++ rely on RAII, don't think they have equivalents in testing libs * Python has `self.addCleanup()`, https://docs.python.org/3/library/unittest.html#unittest.TestCase.addCleanup * Go has `t.Cleanup()`, https://pkg.go.dev/testing#T.Cleanup * Looking at Zig since it also has a `defer`, I guess they just use that, I don't see anything in https://ziglang.org/documentation/master/std/#A%3Bstd:testing * I know nothing about JUnit, but a quick search seems like they rely on @After and @AfterClass annotations, https://junit.org/junit4/javadoc/4.12/org/junit/After.html * I know even less about HUnit, but it looks like it relies on wrapping things via the IO monad, https://hackage.haskell.org/package/HUnit-1.6.2.0/docs/Test-HUnit-Base.html#... * Since we were inspired by TAP, I tried to look at Perl, but didn't immediately see anything that looked equivalent, https://metacpan.org/pod/Test::Most

This is implemented as a resource under the hood, so the ordering between resource cleanup and deferred functions is maintained.

Signed-off-by: David Gow davidgow@google.com

<snip>

diff --git a/include/kunit/resource.h b/include/kunit/resource.h index c0d88b318e90..6db28cd43e9b 100644 --- a/include/kunit/resource.h +++ b/include/kunit/resource.h @@ -387,4 +387,80 @@ static inline int kunit_destroy_named_resource(struct kunit *test, */ void kunit_remove_resource(struct kunit *test, struct kunit_resource *res);

+/**

• • kunit_add_action() - Defer an 'action' (function call) until the test ends.
• • @test: Test case to associate the action with.
• • @func: The function to run on test exit
• • @ctx: Data passed into @func
• • Defer the execution of a function until the test exits, either normally or
• • due to a failure. @ctx is passed as additional context. All functions
• • registered with kunit_add_action() will execute in the opposite order to that
• • they were registered in.
• • This is useful for cleaning up allocated memory and resources.

Re renaming to kunit_add_cleanup(), I think this makes writing the comment easier.

E.g. - kunit_add_action() - Defer an 'action' (function call) until the test ends. + kunit_add_cleanup() - Call a function when the test ends. + ... + This is useful for cleaning up allocated memory and resources.

Daniel