| Message ID | 20250204-printf-kunit-convert-v1-0-ecf1b846a4de@gmail.com |
|---|---|
| Headers | show |
| Series | printf: convert self-test to KUnit | expand |
On Tue, 4 Feb 2025 at 20:36, Tamir Duberstein <tamird@gmail.com> wrote: > > This is one of just 3 remaining "Test Module" kselftests (the others > being bitmap and scanf), the rest having been converted to KUnit. > > I tested this using: > > $ tools/testing/kunit/kunit.py run --arch arm64 --make_options LLVM=1 printf > > I have also sent out a series converting scanf[0]. > > Link: https://lore.kernel.org/all/20250204-scanf-kunit-convert-v3-0-386d7c3ee714@gmail.com/T/#u [0] > Sorry, but NAK, not in this form. Please read the previous threads to understand what is wrong with this mechanical approach. Not only is it wrong, it also actively makes the test suite much less useful. https://lore.kernel.org/lkml/f408efbd-10f7-f1dd-9baa-0f1233cafffc@rasmusvillemoes.dk/ https://lore.kernel.org/lkml/876cc862-56f1-7330-f988-0248bec2fbad@rasmusvillemoes.dk/ https://lore.kernel.org/lkml/0ab618c7-8c5c-00ae-8e08-0c1b99f3bf5c@rasmusvillemoes.dk/ I think the previous attempt was close to something acceptable (around https://lore.kernel.org/lkml/57976ff4-7845-d721-ced1-1fe439000a9b@rasmusvillemoes.dk/), but I don't know what happened to it. Rasmus
On Thu, Feb 6, 2025 at 4:27 AM Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: > > On Tue, 4 Feb 2025 at 20:36, Tamir Duberstein <tamird@gmail.com> wrote: > > > > This is one of just 3 remaining "Test Module" kselftests (the others > > being bitmap and scanf), the rest having been converted to KUnit. > > > > I tested this using: > > > > $ tools/testing/kunit/kunit.py run --arch arm64 --make_options LLVM=1 printf > > > > I have also sent out a series converting scanf[0]. > > > > Link: https://lore.kernel.org/all/20250204-scanf-kunit-convert-v3-0-386d7c3ee714@gmail.com/T/#u [0] > > > > Sorry, but NAK, not in this form. > > Please read the previous threads to understand what is wrong with this > mechanical approach. Not only is it wrong, it also actively makes the > test suite much less useful. > > https://lore.kernel.org/lkml/f408efbd-10f7-f1dd-9baa-0f1233cafffc@rasmusvillemoes.dk/ > https://lore.kernel.org/lkml/876cc862-56f1-7330-f988-0248bec2fbad@rasmusvillemoes.dk/ > https://lore.kernel.org/lkml/0ab618c7-8c5c-00ae-8e08-0c1b99f3bf5c@rasmusvillemoes.dk/ > > I think the previous attempt was close to something acceptable (around > https://lore.kernel.org/lkml/57976ff4-7845-d721-ced1-1fe439000a9b@rasmusvillemoes.dk/), > but I don't know what happened to it. > > Rasmus Thanks Rasmus, I wasn't aware of that prior effort. I've gone through and adopted your comments - the result is a first patch that is much smaller (104 insertions(+), 104 deletions(-)) and failure messages that are quite close to what is emitted now. I've taken care to keep all the control flow the same, as you requested. The previous discussion concluded with a promise to send another patch which didn't happen. May I send a v2 with these changes, or are there more fundamental objections? I'll also cc Arpitha and Brendan. The new failure output: # ip4: EXPECTATION FAILED at lib/printf_kunit.c:95 vsnprintf(buf, 256, "%piS|%pIS", ...) wrote '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1' # ip4: EXPECTATION FAILED at lib/printf_kunit.c:95 vsnprintf(buf, 19, "%piS|%pIS", ...) wrote '127.000.000.001|12', expected '127-000.000.001|12' # ip4: EXPECTATION FAILED at lib/printf_kunit.c:131 kvasprintf(..., "%piS|%pIS", ...) returned '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1' Cheers, Tamir
On Tue, Feb 11, 2025 at 6:34 AM Tamir Duberstein <tamird@gmail.com> wrote: > > https://lore.kernel.org/all/20250210-printf-kunit-convert-v3-1-ee6ac5500f5e@gmail.com/ > > Weirdly the cover letter seems to be missing on lore, should I resend? It's there now. https://lore.kernel.org/all/20250210-printf-kunit-convert-v3-0-ee6ac5500f5e@gmail.com/
On Tue, 11 Feb 2025 at 16:40, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: > > On Tue, Feb 11 2025, David Gow <davidgow@google.com> wrote: > > > On Mon, 10 Feb 2025 at 19:57, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: > >> > >> On Fri, Feb 07 2025, Tamir Duberstein <tamird@gmail.com> wrote: > >> > >> > On Fri, Feb 7, 2025 at 5:01 AM Rasmus Villemoes > >> > <linux@rasmusvillemoes.dk> wrote: > >> >> > >> >> On Thu, Feb 06 2025, Tamir Duberstein <tamird@gmail.com> wrote: > >> >> > >> >> > >> >> I'll have to see the actual code, of course. In general, I find reading > >> >> code using those KUNIT macros quite hard, because I'm not familiar with > >> >> those macros and when I try to look up what they do they turn out to be > >> >> defined in terms of other KUNIT macros 10 levels deep. > >> >> > >> >> But that still leaves a few points. First, I really like that "388 test > >> >> cases passed" tally or some other free-form summary (so that I can see > >> >> that I properly hooked up, compiled, and ran a new testcase inside > >> >> test_number(), so any kind of aggregation on those top-level test_* is > >> >> too coarse). > >> > > >> > This one I'm not sure how to address. What you're calling test cases > >> > here would typically be referred to as assertions, and I'm not aware > >> > of a way to report a count of assertions. > >> > > >> > >> I'm not sure that's accurate. > >> > >> The thing is, each of the current test() instances results in four > >> different tests being done, which is roughly why we end up at the 4*97 > >> == 388, but each of those tests has several assertions being done - > >> depending on which variant of the test we're doing (i.e. the buffer > >> length used or if we're passing it through kasprintf), we may do only > >> some of those assertions, and we do an early return in case one of those > >> assertions fail (because it wouldn't be safe to do the following > >> assertions, and the test as such has failed already). So there are far > >> more assertions than those 388. > >> > >> OTOH, that the number reported is 388 is more a consequence of the > >> implementation than anything explicitly designed. I can certainly live > >> with 388 being replaced by 97, i.e. that each current test() invocation > >> would count as one KUNIT case, as that would still allow me to detect a > >> PEBKAC when I've added a new test() instance and failed to actually run > >> that. > > > > It'd be possible to split things up further into tests, at the cost of > > it being a more extensive refactoring, if having the more granular > > count tracked by KUnit were desired. > > I think the problem is that kunit is simply not a good framework to do > these kinds of tests in, and certainly it's very hard to retrofit kunit > after the fact. > I think I'd have to disagree on the whole (though I'm admittedly biased in KUnit's favour), but I can definitely see that the printf tests do provide some unique challenges, and that either way, a port would require either some code churn or bloat, a need to reinterpret things (such as what unit a 'test' is), or both. Ultimately, I don't want to force KUnit on anyone if it's going to make things more difficult, so it's ultimately up to you. My personal feeling is that this could work well as a KUnit test, but due to the churn involved, it may not be worth it if no-one wants to take advantage of the tooling. > It'd also be possible to make > > these more explicitly data driven via a parameterised test (so each > > input/output pair is listed in an array, and automatically gets > > converted to a KUnit subtest). > > So that "array of input/output" very much doesn't work for these > specific tests: We really want the format string/varargs to be checked > by the compiler, and besides, there's no way to store the necessary > varargs and generate a call from those in an array. Moreover, we verify a > lot more than just that the correct string is produced; it's also a > matter of the right return value regardless of the passed buffer size, etc. Ah, that makes sense. I suspect with enough work and some friendly compiler developers, this could be make to work, but it definitely doesn't seem worth the effort to me. > That's also why is nigh impossible to simply change __test() into > (another) macro that expands to something that defines an individual > struct kunit_case, because the framework is really built around the > notion that each case can be represented by a void function call and the > name of the test is the stringification of the function name. Yeah: it may be possible to do something with KUnit's parameter generating functions (you can have a function which generates a void* test context, as well as a string test name: this could be a struct with a format string and a va_list), but it's definitely getting complicated. > So I don't mind the conversion to kunit if that really helps other > people, as long as the basic functionality is still present and doesn't > impede future extensions - and certainly I don't want to end up in a > situation where somebody adds a new %p extension but cannot really add a > test for it because kunit makes that hard. > > But I hope you all agree that it doesn't make much _sense_ to consider > test_number() and test_string() and so on individual "test cases"; the > atomic units of test being done in the printf suite is each invocation > of the __test() function, with one specific format string/varargs > combination. I think this is -- to some extent -- a matter of interpretation. I don't think it's wrong to use KUnit test cases to refer to a "thing being tested" (e.g., a specific format specifier) rather than an "individual invocation": lots of KUnit tests already group very related things together. But given the way there are several "checks" within each __test() invocation mirrors this already, I understand why it'd make sense to keep that as the "test case". I don't have any immediate plans personally to work on the printf/scanf code, so your opinion here definitely matters more than mine. But if this does end up as a KUnit test, I'll definitely keep an eye on it as part of my regular KUnit test runs. Cheers, -- David > > Rasmus
This is one of just 3 remaining "Test Module" kselftests (the others being bitmap and scanf), the rest having been converted to KUnit. I tested this using: $ tools/testing/kunit/kunit.py run --arch arm64 --make_options LLVM=1 printf I have also sent out a series converting scanf[0]. Link: https://lore.kernel.org/all/20250204-scanf-kunit-convert-v3-0-386d7c3ee714@gmail.com/T/#u [0] Signed-off-by: Tamir Duberstein <tamird@gmail.com> --- Tamir Duberstein (2): printf: convert self-test to KUnit printf: break kunit into test cases Documentation/core-api/printk-formats.rst | 2 +- MAINTAINERS | 2 +- arch/m68k/configs/amiga_defconfig | 1 - arch/m68k/configs/apollo_defconfig | 1 - arch/m68k/configs/atari_defconfig | 1 - arch/m68k/configs/bvme6000_defconfig | 1 - arch/m68k/configs/hp300_defconfig | 1 - arch/m68k/configs/mac_defconfig | 1 - arch/m68k/configs/multi_defconfig | 1 - arch/m68k/configs/mvme147_defconfig | 1 - arch/m68k/configs/mvme16x_defconfig | 1 - arch/m68k/configs/q40_defconfig | 1 - arch/m68k/configs/sun3_defconfig | 1 - arch/m68k/configs/sun3x_defconfig | 1 - arch/powerpc/configs/ppc64_defconfig | 1 - lib/Kconfig.debug | 20 +- lib/Makefile | 2 +- lib/printf_kunit.c | 757 ++++++++++++++++++++++++++ lib/test_printf.c | 863 ------------------------------ tools/testing/selftests/lib/config | 1 - tools/testing/selftests/lib/printf.sh | 4 - 21 files changed, 777 insertions(+), 887 deletions(-) --- base-commit: a86bf2283d2c9769205407e2b54777c03d012939 change-id: 20250131-printf-kunit-convert-fd4012aa2ec6 Best regards,