On Thu, Feb 28, 2019 at 10:02 AM Stephen Boyd sboyd@kernel.org wrote:
Quoting Brendan Higgins (2019-02-28 01:03:24)
On Tue, Feb 26, 2019 at 12:35 PM Stephen Boyd sboyd@kernel.org wrote:
when they need to abort and then the test runner would detect that error via the return value from the 'run test' function. That would be a more direct approach, but also more verbose than a single KUNIT_ASSERT() line. It would be more kernel idiomatic too because the control flow
Yeah, I was intentionally going against that idiom. I think that idiom makes test logic more complicated than it needs to be, especially if the assertion failure happens in a helper function; then you have to pass that error all the way back up. It is important that test code should be as simple as possible to the point of being immediately obviously correct at first glance because there are no tests for tests.
The idea with assertions is that you use them to state all the preconditions for your test. Logically speaking, these are the premises of the test case, so if a premise isn't true, there is no point in continuing the test case because there are no conclusions that can be drawn without the premises. Whereas, the expectation is the thing you are trying to prove. It is not used universally in x-unit style test frameworks, but I really like it as a convention. You could still express the idea of a premise using the above idiom, but I think KUNIT_ASSERT_* states the intended idea perfectly.
Fair enough. It would be great if these sorts of things were described in the commit text.
Good point. Will fix.
Is the assumption that things like held locks and refcounted elements won't exist when one of these assertions is made? It sounds like some of the cleanup logic could be fairly complicated if a helper function changes some state and then an assert fails and we have to unwind all the state from a corrupt location. A similar problem exists for a test timeout too. How do we get back to a sane state if the test locks up for a long time? Just don't try?
It depends on the situation, if it is part of a KUnit test itself (probably not code under test), then you can use the kunit_resource API: https://lkml.org/lkml/2019/2/14/1125; it is inspired by the devm_* family of functions, such that when a KUnit test case ends, for any reason, all the kunit_resources are automatically cleaned up. Similarly, kunit_module.exit is called at the end of every test case, regardless of how it terminates.
isn't hidden inside a macro and it isn't intimately connected with kthreads and completions.
Yeah, I wasn't a fan of that myself, but it was broadly available. My previous version (still the architecture specific version for UML, not in this patchset though) relies on UML_LONGJMP, but is obviously only works on UML. A number of people wanted support for other architectures. Rob and Luis specifically wanted me to provide a version of abort that would work on any architecture, even if it only had reduced functionality; I thought this fit the bill okay.
Ok.
diff --git a/kunit/test.c b/kunit/test.c index d18c50d5ed671..6e5244642ab07 100644 --- a/kunit/test.c +++ b/kunit/test.c
[...]
+static void kunit_generic_throw(struct kunit_try_catch *try_catch) +{
try_catch->context.try_result = -EFAULT;complete_and_exit(try_catch->context.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->context.try_completion, 0);The exit code doesn't matter, right? If so, it might be clearer to just return 0 from this function because kthreads exit themselves as far as I recall.
You mean complete and then return?
Yes. I was confused for a minute because I thought the exit code was checked, but it isn't. Instead, the try_catch->context.try_result is where the test result goes, so calling exit explicitly doesn't seem to be important here, but it is important in the throw case.
Yep.
else if (exit_code)kunit_err(test, "Unknown error: %d", exit_code);+}
+void kunit_generic_try_catch_init(struct kunit_try_catch *try_catch) +{
try_catch->run = kunit_generic_run_try_catch;Is the idea that 'run' would be anything besides 'kunit_generic_run_try_catch'? If it isn't going to be different, then
Yeah, it can be overridden with an architecture specific version.
maybe it's simpler to just have a function like kunit_generic_run_try_catch() that is called by the unit tests instead of having to write 'try_catch->run(try_catch)' and indirect for the basic case. Maybe I've missed the point entirely though and this is all scaffolding for more complicated exception handling later on.
Yeah, the idea is that different architectures can override exception handling with their own implementation. This is just the generic one. For example, UML has one that doesn't depend on kthreads or completions; the UML version also allows recovery from some segfault conditions.
Ok, got it. It may still be nice to have a wrapper or macro for that try_catch->run(try_catch) statement so we don't have to know that a try_catch struct has a run member.
static inline void kunit_run_try_catch(struct kunit_try_catch *try_catch) { try_catch->run(try_catch); }
Makes sense. Will fix in the next revision.
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Brendan Higgins