Re: [PATCH v12 09/18] kunit: test: add support for test abort

Brendan Higgins
2019-08-13T04:58:12Z

On Mon, Aug 12, 2019 at 9:22 PM Stephen Boyd <sboyd@kernel.org> wrote:
>
> Quoting Brendan Higgins (2019-08-12 11:24:12)
> > diff --git a/include/kunit/test.h b/include/kunit/test.h
> > index 2625bcfeb19ac..93381f841e09f 100644
> > --- a/include/kunit/test.h
> > +++ b/include/kunit/test.h
> > @@ -13,6 +13,7 @@
> > #include <linux/types.h>
> > #include <linux/slab.h>
> > #include <kunit/assert.h>
> > +#include <kunit/try-catch.h>
> >
> > struct kunit_resource;
> >
> > @@ -167,6 +168,7 @@ struct kunit {
> >
> > /* private: internal use only. */
> > const char *name; /* Read only after initialization! */
> > + struct kunit_try_catch try_catch;
> > /*
> > * success starts as true, and may only be set to false during a test
> > * case; thus, it is safe to update this across multiple threads using
> > @@ -176,6 +178,11 @@ struct kunit {
> > */
> > bool success; /* Read only after test_case finishes! */
> > spinlock_t lock; /* Gaurds all mutable test state. */
> > + /*
> > + * death_test may be both set and unset from multiple threads in a test
> > + * case.
> > + */
> > + bool death_test; /* Protected by lock. */
> > /*
> > * Because resources is a list that may be updated multiple times (with
> > * new resources) from any thread associated with a test case, we must
> > @@ -184,6 +191,13 @@ struct kunit {
> > struct list_head resources; /* Protected by lock. */
> > };
> >
> > +static inline void kunit_set_death_test(struct kunit *test, bool death_test)
> > +{
> > + spin_lock(&test->lock);
> > + test->death_test = death_test;
> > + spin_unlock(&test->lock);
> > +}
>
> These getters and setters are using spinlocks again. It doesn't make any
> sense. It probably needs a rework like was done for the other bool
> member, success.

No, this is intentional. death_test can transition from false to true
and then back to false within the same test. Maybe that deserves a
comment?

> > +
> > void kunit_init_test(struct kunit *test, const char *name);
> >
> > int kunit_run_tests(struct kunit_suite *suite);
> > diff --git a/include/kunit/try-catch.h b/include/kunit/try-catch.h
> > new file mode 100644
> > index 0000000000000..8a414a9af0b64
> > --- /dev/null
> > +++ b/include/kunit/try-catch.h
> > @@ -0,0 +1,69 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * An API to allow a function, that may fail, to be executed, and recover in a
> > + * controlled manner.
> > + *
> > + * Copyright (C) 2019, Google LLC.
> > + * Author: Brendan Higgins <brendanhiggins@google.com>
> > + */
> > +
> > +#ifndef _KUNIT_TRY_CATCH_H
> > +#define _KUNIT_TRY_CATCH_H
> > +
> > +#include <linux/types.h>
> > +
> > +typedef void (*kunit_try_catch_func_t)(void *);
> > +
> > +struct kunit;
>
> Forward declare struct completion?

Sure. Will do.

> > +
> > +/*
> > + * struct kunit_try_catch - provides a generic way to run code which might fail.
> > + * @context: used to pass user data to the try and catch functions.
> > + *
> > + * kunit_try_catch provides a generic, architecture independent way to execute
> > + * an arbitrary function of type kunit_try_catch_func_t which may bail out by
> > + * calling kunit_try_catch_throw(). If kunit_try_catch_throw() is called, @try
> > + * is stopped at the site of invocation and @catch is catch is called.
> > + *
> > + * struct kunit_try_catch provides a generic interface for the functionality
> > + * needed to implement kunit->abort() which in turn is needed for implementing
> > + * assertions. Assertions allow stating a precondition for a test simplifying
> > + * how test cases are written and presented.
> > + *
> > + * Assertions are like expectations, except they abort (call
> > + * kunit_try_catch_throw()) when the specified condition is not met. This is
> > + * useful when you look at a test case as a logical statement about some piece
> > + * of code, where assertions are the premises for the test case, and the
> > + * conclusion is a set of predicates, rather expectations, that must all be
> > + * true. If your premises are violated, it does not makes sense to continue.
> > + */
> > +struct kunit_try_catch {
> > + /* private: internal use only. */
> > + struct kunit *test;
> > + struct completion *try_completion;
> > + int try_result;
> > + kunit_try_catch_func_t try;
> > + kunit_try_catch_func_t catch;
>
> Can these other variables be documented in the kernel doc? And should
> context be marked as 'public'?

Sure, I can document them.

But I don't think context should be public; it should only be accessed
by kunit_try_catch_* functions. context should only be populated by
*_init, and will be passed into *try and *catch when they are called
internally.

> > + void *context;
> > +};
> > +
> > +void kunit_try_catch_init(struct kunit_try_catch *try_catch,
> > + struct kunit *test,
> > + kunit_try_catch_func_t try,
> > + kunit_try_catch_func_t catch);
> > +
> > +void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context);
> > +
> > +void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch);
> > +
> > +static inline int kunit_try_catch_get_result(struct kunit_try_catch *try_catch)
> > +{
> > + return try_catch->try_result;
> > +}
> > +
> > +/*
> > + * Exposed for testing only.
>
> Ugh that's sad. I hope we don't expose more functions just for testing
> in other cases.

I don't think I am in any other cases in this patchset. I agree that
it is generally bad to expose a private function for testing purposes,
but I didn't see a better way here.

> > + */
> > +void kunit_generic_try_catch_init(struct kunit_try_catch *try_catch);
> > +
> > +#endif /* _KUNIT_TRY_CATCH_H */
> > diff --git a/kunit/test.c b/kunit/test.c
> > index e5080a2c6b29c..995cb53fe4ee9 100644
> > --- a/kunit/test.c
> > +++ b/kunit/test.c
> > @@ -7,13 +7,26 @@
> > */
> >
> > #include <linux/kernel.h>
> > +#include <linux/sched/debug.h>
> > #include <kunit/test.h>
> > +#include <kunit/try-catch.h>
> >
> > static void kunit_set_failure(struct kunit *test)
> > {
> > WRITE_ONCE(test->success, false);
> > }
> >
> > +static bool kunit_get_death_test(struct kunit *test)
> > +{
> > + bool death_test;
> > +
> > + spin_lock(&test->lock);
> > + death_test = test->death_test;
> > + spin_unlock(&test->lock);
> > +
> > + return death_test;
> > +}
> > +
> > static int kunit_vprintk_emit(int level, const char *fmt, va_list args)
> > {
> > return vprintk_emit(0, level, NULL, 0, fmt, args);
> > @@ -158,6 +171,21 @@ static void kunit_fail(struct kunit *test, struct kunit_assert *assert)
> > kunit_print_string_stream(test, stream);
> > }
> >
> > +void __noreturn kunit_abort(struct kunit *test)
> > +{
> > + kunit_set_death_test(test, true);
> > +
> > + kunit_try_catch_throw(&test->try_catch);
> > +
> > + /*
> > + * Throw could not abort from test.
> > + *
> > + * XXX: we should never reach this line! As kunit_try_catch_throw is
> > + * marked __noreturn.
> > + */
> > + WARN_ONCE(true, "Throw could not abort from test!\n");
>
> Should this just be a BUG_ON? It's supposedly impossible.

It should be impossible; it will only reach this line if there is a
bug in kunit_try_catch_throw. The reason I didn't use BUG_ON was
because I previously got yelled at for having BUG_ON in this code
path.

Nevertheless, I think BUG_ON is more correct, so if you will stand by
it, then that's what I will do.

> > +}
> > +
> > void kunit_do_assertion(struct kunit *test,
> > struct kunit_assert *assert,
> > bool pass,
> > @@ -176,6 +204,9 @@ void kunit_do_assertion(struct kunit *test,
> > kunit_fail(test, assert);
> >
> > va_end(args);
> > +
> > + if (assert->type == KUNIT_ASSERTION)
> > + kunit_abort(test);
> > }
> >
> > void kunit_init_test(struct kunit *test, const char *name)
> > @@ -184,36 +215,154 @@ void kunit_init_test(struct kunit *test, const char *name)
> > INIT_LIST_HEAD(&test->resources);
> > test->name = name;
> > test->success = true;
> > + test->death_test = false;
> > }
> >
> > /*
> > - * Performs all logic to run a test case.
> > + * Initializes and runs test case. Does not clean up or do post validations.
> > */
> > -static void kunit_run_case(struct kunit_suite *suite,
> > - struct kunit_case *test_case)
> > +static void kunit_run_case_internal(struct kunit *test,
> > + struct kunit_suite *suite,
> > + struct kunit_case *test_case)
> > {
> > - struct kunit test;
> > -
> > - kunit_init_test(&test, test_case->name);
> > -
> > if (suite->init) {
> > int ret;
> >
> > - ret = suite->init(&test);
> > + ret = suite->init(test);
> > if (ret) {
> > - kunit_err(&test, "failed to initialize: %d\n", ret);
> > - kunit_set_failure(&test);
> > - test_case->success = test.success;
> > + kunit_err(test, "failed to initialize: %d\n", ret);
> > + kunit_set_failure(test);
> > return;
> > }
> > }
> >
> > - test_case->run_case(&test);
> > + test_case->run_case(test);
> > +}
> > +
> > +static void kunit_case_internal_cleanup(struct kunit *test)
> > +{
> > + kunit_cleanup(test);
> > +}
> >
> > +/*
> > + * Performs post validations and cleanup after a test case was run.
> > + * XXX: Should ONLY BE CALLED AFTER kunit_run_case_internal!
> > + */
> > +static void kunit_run_case_cleanup(struct kunit *test,
> > + struct kunit_suite *suite)
> > +{
> > if (suite->exit)
> > - suite->exit(&test);
> > + suite->exit(test);
> > +
> > + kunit_case_internal_cleanup(test);
> > +}
> > +
> > +/*
> > + * Handles an unexpected crash in a test case.
> > + */
> > +static void kunit_handle_test_crash(struct kunit *test,
> > + struct kunit_suite *suite,
> > + struct kunit_case *test_case)
> > +{
> > + kunit_err(test, "kunit test case crashed!");
>
> Does this need a newline?

Yep, nice catch. I thought I grepped for all the instance a while ago,
but I apparently missed this one.

> > + /*
> > + * TODO(brendanhiggins@google.com): This prints the stack trace up
> > + * through this frame, not up to the frame that caused the crash.
> > + */
> > + show_stack(NULL, NULL);
> > +
> > + kunit_case_internal_cleanup(test);
> > +}
> > +
> > +struct kunit_try_catch_context {
> > + struct kunit *test;
> > + struct kunit_suite *suite;
> > + struct kunit_case *test_case;
> > +};
> > +
> > +static void kunit_try_run_case(void *data)
> > +{
> > + struct kunit_try_catch_context *ctx = data;
> > + struct kunit *test = ctx->test;
> > + struct kunit_suite *suite = ctx->suite;
> > + struct kunit_case *test_case = ctx->test_case;
> > +
> > + /*
> > + * kunit_run_case_internal may encounter a fatal error; if it does,
> > + * abort will be called, this thread will exit, and finally the parent
> > + * thread will resume control and handle any necessary clean up.
> > + */
> > + kunit_run_case_internal(test, suite, test_case);
> > + /* This line may never be reached. */
> > + kunit_run_case_cleanup(test, suite);
> > +}
> > +
> > +static void kunit_catch_run_case(void *data)
> > +{
> > + struct kunit_try_catch_context *ctx = data;
> > + struct kunit *test = ctx->test;
> > + struct kunit_suite *suite = ctx->suite;
> > + struct kunit_case *test_case = ctx->test_case;
> > + int try_exit_code = kunit_try_catch_get_result(&test->try_catch);
> > +
> > + if (try_exit_code) {
> > + kunit_set_failure(test);
> > + /*
> > + * Test case could not finish, we have no idea what state it is
> > + * in, so don't do clean up.
> > + */
> > + if (try_exit_code == -ETIMEDOUT)
> > + kunit_err(test, "test case timed out\n");
> > + /*
> > + * Unknown internal error occurred preventing test case from
> > + * running, so there is nothing to clean up.
> > + */
> > + else
> > + kunit_err(test, "internal error occurred preventing test case from running: %d\n",
> > + try_exit_code);
>
> Nitpick: I would add braces here because you make the if statement into
> multi-line arms for each case.

Will do. I think it looks better with braces anyway.

> > + return;
> > + }
> > +
> > + if (kunit_get_death_test(test)) {
> > + /*
> > + * EXPECTED DEATH: kunit_run_case_internal encountered
> > + * anticipated fatal error. Everything should be in a safe
> > + * state.
> > + */
> > + kunit_run_case_cleanup(test, suite);
> > + } else {
> > + /*
> > + * UNEXPECTED DEATH: kunit_run_case_internal encountered an
> > + * unanticipated fatal error. We have no idea what the state of
> > + * the test case is in.
> > + */
> > + kunit_handle_test_crash(test, suite, test_case);
> > + kunit_set_failure(test);
>
> Like was done here.

Sorry, like what?

> > + }
> > +}
> > +
> > +/*
> > + * Performs all logic to run a test case. It also catches most errors that
> > + * occurs in a test case and reports them as failures.
>
> s/occurs/occur/

Damn, I should go over all these with spell check. Will fix, thanks!

> > + */
> > +static void kunit_run_case_catch_errors(struct kunit_suite *suite,
> [...]
> > diff --git a/kunit/try-catch.c b/kunit/try-catch.c
> > new file mode 100644
> > index 0000000000000..de580f074387b
> > --- /dev/null
> > +++ b/kunit/try-catch.c
> > @@ -0,0 +1,95 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * An API to allow a function, that may fail, to be executed, and recover in a
> > + * controlled manner.
> > + *
> > + * Copyright (C) 2019, Google LLC.
> > + * Author: Brendan Higgins <brendanhiggins@google.com>
> > + */
> > +
> > +#include <kunit/try-catch.h>
> > +#include <kunit/test.h>
> > +#include <linux/completion.h>
> > +#include <linux/kthread.h>
> > +
> > +void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)
> > +{
> > + try_catch->try_result = -EFAULT;
> > + complete_and_exit(try_catch->try_completion, -EFAULT);
> > +}
> > +
> > +static int kunit_generic_run_threadfn_adapter(void *data)
> > +{
> > + struct kunit_try_catch *try_catch = data;
> > +
> > + try_catch->try(try_catch->context);
> > +
> > + complete_and_exit(try_catch->try_completion, 0);
> > +}
> > +
> > +void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
> > +{
> > + DECLARE_COMPLETION_ONSTACK(try_completion);
> > + struct kunit *test = try_catch->test;
> > + struct task_struct *task_struct;
> > + int exit_code, status;
> > +
> > + try_catch->context = context;
> > + try_catch->try_completion = &try_completion;
> > + try_catch->try_result = 0;
> > + task_struct = kthread_run(kunit_generic_run_threadfn_adapter,
> > + try_catch,
> > + "kunit_try_catch_thread");
> > + if (IS_ERR(task_struct)) {
> > + try_catch->catch(try_catch->context);
> > + return;
> > + }
> > +
> > + /*
> > + * TODO(brendanhiggins@google.com): We should probably have some type of
> > + * variable timeout here. The only question is what that timeout value
> > + * should be.
> > + *
> > + * The intention has always been, at some point, to be able to label
> > + * tests with some type of size bucket (unit/small, integration/medium,
> > + * large/system/end-to-end, etc), where each size bucket would get a
> > + * default timeout value kind of like what Bazel does:
> > + * https://docs.bazel.build/versions/master/be/common-definitions.html#test.size
> > + * There is still some debate to be had on exactly how we do this. (For
> > + * one, we probably want to have some sort of test runner level
> > + * timeout.)
> > + *
> > + * For more background on this topic, see:
> > + * https://mike-bland.com/2011/11/01/small-medium-large.html
> > + */
> > + status = wait_for_completion_timeout(&try_completion,
> > + 300 * MSEC_PER_SEC); /* 5 min */
> > + if (status < 0) {
>
> wait_for_completion_timeout() doesn't return a negative value on
> timeout. It returns 0. Please rename 'status' to 'time_remaining' and
> test with if (!time_remaining) instead or some other suitably named
> variable name indicating that the return value is the time remaining
> before the timeout.

Crap, I knew that. Sorry, I wasn't thinking.

> May also want to clamp this to the hung task timeout value, which is
> typically less than 5 minutes. Otherwise, the hung task detector may
> find the problem first before this timeout happens.

Makes sense. Will fix.

> > + kunit_err(test, "try timed out\n");
> > + try_catch->try_result = -ETIMEDOUT;
> > + }