On Sun, Oct 25, 2020 at 10:48:38PM +0100, Rasmus Villemoes wrote:
This is a bit of a mixed bag.
The background is that I have some sort() and list_sort() rework planned, but as part of that series I want to extend their their test suites somewhat to make sure I don't goof up - and I want to use lots of random list lengths with random contents to increase the chance of somebody eventually hitting "hey, sort() is broken when the length is 3 less than a power of 2 and only the last two elements are out of order". But when such a case is hit, it's vitally important that the developer can reproduce the exact same test case, which means using a deterministic sequence of random numbers.
Since Petr noticed [1] the non-determinism in test_printf in connection with Arpitha's work on rewriting it to kunit, this prompted me to use test_printf as a first place to apply that principle, and get the infrastructure in place that will avoid repeating the "module parameter/seed the rnd_state/report the seed used" boilerplate in each module.
Shuah, assuming the kselftest_module.h changes are ok, I think it's most natural if you carry these patches, though I'd be happy with any other route as well.
Completely in favour of this.
Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
One note though. AFAIU the global variables are always being used in the modules that include the corresponding header. Otherwise we might have an extra warning(s). I believe you have compiled with W=1 to exclude other cases.
[1] https://lore.kernel.org/lkml/20200821113710.GA26290@alley/
Rasmus Villemoes (4): prandom.h: add *_state variant of prandom_u32_max kselftest_module.h: unconditionally expand the KSTM_MODULE_GLOBALS() macro kselftest_module.h: add struct rnd_state and seed parameter lib/test_printf.c: use deterministic sequence of random numbers
Documentation/dev-tools/kselftest.rst | 2 -- include/linux/prandom.h | 29 ++++++++++++++++ lib/test_bitmap.c | 3 -- lib/test_printf.c | 13 ++++--- lib/test_strscpy.c | 2 -- tools/testing/selftests/kselftest_module.h | 40 ++++++++++++++++++---- 6 files changed, 72 insertions(+), 17 deletions(-)
-- 2.23.0