Re: Sporadic regmap unit test failure in raw_sync

[Guenter Roeck]

On 2/8/24 14:10, Mark Brown wrote:
> On Thu, Feb 08, 2024 at 01:45:13PM -0800, Guenter Roeck wrote:
>
> >      # raw_sync: EXPECTATION FAILED at drivers/base/regmap/regmap-kunit.c:1305
> >      Expected &hw_buf[6] != val, but
> >          &hw_buf[6] ==
> >           57  30
> >          val ==
> >           57  30
> >          not ok 4 rbtree-big
> >          ok 5 maple-little
> >          ok 6 maple-big
> >      # raw_sync: pass:5 fail:1 skip:0 total:6
> >      not ok 25 raw_sync
>
> > This is with regmap: 'kunit: fix raw noinc write test wrapping'
> > applied on top of the upstream kernel (v6.8-rc3-47-g047371968ffc).
> > So far I have seen it only once, with the x86_64:q35 emulation in qemu.
>
> I guess it's possible that we randomly generated the same value for the
> initial and modified values here?

Guess so. Presumably that means we'll see the problem on average once every
65,536 tests or so ? Lucky me ...

Would it make sense to read the value from regmap and invert it instead of
using random numbers ?

Guenter