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

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Date: Thu, 8 Feb 2024 22:17:02 -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?


I think the diffs below should fix the problem. Would that do, or do you
have a better idea ?

Thanks,
Guenter

---
diff --git a/drivers/base/regmap/regmap-kunit.c b/drivers/base/regmap/regmap-kunit.c
index 4eb18f5d3265..666ece18726f 100644
--- a/drivers/base/regmap/regmap-kunit.c
+++ b/drivers/base/regmap/regmap-kunit.c
@@ -1266,7 +1266,11 @@ static void raw_sync(struct kunit *test)

         hw_buf = (u16 *)data->vals;

-       get_random_bytes(&val, sizeof(val));
+       /* values in val[] must be different from those in hw_buf[] */
+       val[0] = ~hw_buf[2];
+       if (val[0] == hw_buf[6])
+               val[0]++
+       val[1] = ~hw_buf[3];

         /* Do a regular write and a raw write in cache only mode */
         regcache_cache_only(map, true);