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SubjectRe: lock warnings in dev_addr_lists test
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On 2/29/24 00:10, David Gow wrote:
> On Thu, 29 Feb 2024 at 03:45, Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> Hi,
>>
>> when running the dev_addr_lists unit test with lock debugging enabled,
>> I always get the following lockdep warning.
>>
>> [ 7.031327] ====================================
>> [ 7.031393] WARNING: kunit_try_catch/1886 still has locks held!
>> [ 7.031478] 6.8.0-rc6-00053-g0fec7343edb5-dirty #1 Tainted: G W N
>> [ 7.031728] ------------------------------------
>> [ 7.031816] 1 lock held by kunit_try_catch/1886:
>> [ 7.031896] #0: ffffffff8ed35008 (rtnl_mutex){+.+.}-{3:3}, at: dev_addr_test_init+0x6a/0x100
>>
>> Instrumentation shows that dev_addr_test_exit() is called, but only
>> after the warning fires.
>>
>> Is this a problem with kunit tests or a problem with this specific test ?
>
> A bit of both, I think. KUnit test cleanup is not guaranteed to run in
> the same thread as the test, so that definitely is triggering lockdep
> warnings.
>
> On the other hand, we really should make this particular case work in
> KUnit. Ideally test cleanup will happen on the test thread first, and
> only fall back to another test if the test thread otherwise aborted.
>
> So, this is probably something we won't be able to fix if the test
> fails, but it definitely shouldn't be happening here where it passes.
> I'll look into fixing that.
>

Here is a different warning, from the same test:

[ 10.622270] =====================================
[ 10.622346] WARNING: bad unlock balance detected!
[ 10.622481] 6.8.0-rc6 #1 Tainted: G N
[ 10.622624] -------------------------------------
[ 10.622698] kunit_try_catch/1354 is trying to release lock (rtnl_mutex) at:
[ 10.623123] [<ffffd7c5cbdb75cc>] __rtnl_unlock+0x3c/0x84
[ 10.623538] but there are no more locks to release!

That seems to be kind of the opposite problem. I noticed this only
once in my tests, so it is much rarer than the other warning.

Guenter


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