Re: [PATCH 2/4] test-ww_mutex: Report errors from stress workers

[Haakon Bugge]

> On 9 Jul 2026, at 02:03, John Stultz <jstultz@xxxxxxxxxx> wrote:
> 
> On Thu, Jun 18, 2026 at 10:52 AM John Stultz <jstultz@xxxxxxxxxx> wrote:
>> On Wed, Jun 17, 2026 at 5:13 AM Håkon Bugge <haakon.bugge@xxxxxxxxxx> wrote:
>>> 
>>> If any of stress_one_work(), stress_reorder_work(), or
>>> stress_inorder_work() fails, the error is not conveyed back to the
>>> test harness function stress().
>>> 
>>> We may then see in the log:
>>> 
>>>   stress (stress_inorder_work) failed with -35
>>>   Beginning ww (die) mutex selftests
>>>   All ww mutex selftests passed
>>> 
>>> Besides being a contradiction by terms, the failure to return error
>>> from said worker functions leads to false-positive results.
>>> 
>>> We fix that by adding a *result* variable to *struct stress*, update
>>> it in said worker functions, and finally, in stress(), scan the
>>> *stress_array* and report the first error if any.
>>> 
>>> Fixes: 2a0c11282881 ("locking/ww_mutex: Add kselftests for ww_mutex stress")
>>> Signed-off-by: Håkon Bugge <haakon.bugge@xxxxxxxxxx>
>> 
>> Acked-by: John Stultz <jstultz@xxxxxxxxxx>
> 
> I did catch one issue with this patch in testing.  Where as without
> this change, if there was a failure in the first run during
> test_ww_mutex_init(), you could still run the test again manually via
> the sysfs interface without unloading and reloading.
> 
> But with this change, since the error is reported, the module_init
> function sees the error and bails out, removing the sysfs interface.
> If its a module, you can just reload it, but if it is built-in then
> its stuck and can't be rerun.
> 
> So we might want to tweak test_ww_mutex_init() with this patch and
> include something like (whitespace corrupted, just for illustration
> here):
>        ret = run_test_classes();
>        mutex_unlock(&run_lock);
> 
> -       if (!ret)
> +       if (!ret || IS_BUILTIN(CONFIG_WW_MUTEX_SELFTEST))
>                return 0;
> 
>        sysfs_remove_group(test_ww_mutex_kobj, &attr_group);
> 
> ?

Good catch. I must admit I did not test with it built-in. Let me add the above in the fortcoming v2 :-)


Thxs, Håkon