On 26/10/2020 11.59, Andy Shevchenko wrote:
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
Thanks.
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.
Yes, I unconditionally define the two new variables. gcc doesn't warn about them being unused, since they are referenced from inside a
if (0) {}
block. And when those references are the only ones, gcc is smart enough to elide the static variables completely, so they don't even take up space in .data (or .init.data) - you can verify by running nm on test_printf.o and test_bitmap.o - the former has 'seed' and 'rnd_state' symbols, the latter does not.
I did it that way to reduce the need for explicit preprocessor conditionals inside C functions.
Rasmus