linux-kernel - Re: Sporadic regmap unit test failure in raw

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Date: Thu, 8 Feb 2024 14:26:02 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Mark Brown <broonie@...nel.org>
Cc: linux-kernel@...r.kernel.org
Subject: Re: Sporadic regmap unit test failure in raw_sync

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