Re: [PATCH] sparc/pci: Make pci_poke_lock a raw_spinlock_t.

Waiman Long
2024-11-25T22:33:57Z

On 11/25/24 4:54 PM, Guenter Roeck wrote:
> On 11/25/24 13:29, Waiman Long wrote:
>>
>> On 11/25/24 4:25 PM, Guenter Roeck wrote:
>>> On 11/25/24 12:54, Waiman Long wrote:
>>>>
>>>> On 11/25/24 3:23 PM, Guenter Roeck wrote:
>>>>> On 11/25/24 12:06, Guenter Roeck wrote:
>>>>>> On 11/25/24 11:33, Waiman Long wrote:
>>>>>> [ ... ]
>>>>>>>> Fixing that finally gives me a clean run. Nevertheless, that
>>>>>>>> makes me wonder:
>>>>>>>> Should I just disable CONFIG_PROVE_RAW_LOCK_NESTING for sparc
>>>>>>>> runtime tests ?
>>>>>>>
>>>>>>> If no one is tryng to ever enable PREEMPT_RT on SPARC, I suppose
>>>>>>> you could disable CONFIG_PROVE_RAW_LOCK_NESTING to avoid the
>>>>>>> trouble.
>>>>>>>
>>>>>>
>>>>>> SGTM. I'll do that unless someone gives me a good reason to keep
>>>>>> it enabled.
>>>>>>
>>>>>
>>>>> Actually it can not be disabled with a configuration flag. It is
>>>>> automatically enabled. I'll have to disable PROVE_LOCKING to
>>>>> disable it.
>>>>>
>>>>> config PROVE_RAW_LOCK_NESTING
>>>>>         bool                    <---- no longer user configurable
>>>>>         depends on PROVE_LOCKING
>>>>>         default y
>>>>>         help
>>>>>          Enable the raw_spinlock vs. spinlock nesting checks which
>>>>> ensure
>>>>>          that the lock nesting rules for PREEMPT_RT enabled
>>>>> kernels are
>>>>>          not violated.
>>>>>
>>>>> I don't really like that, and I don't understand the logic behind it,
>>>>> but it is what it is.
>>>>>
>>>>> FWIW, the description of commit 560af5dc839 is misleading. It says
>>>>> "Enable
>>>>> PROVE_RAW_LOCK_NESTING _by default_" (emphasis mine). That is not
>>>>> what the
>>>>> commit does. It force-enables PROVE_RAW_LOCK_NESTING if
>>>>> PROVE_LOCKING is
>>>>> enabled. It is all or nothing.
>>>>>
>>>> I think we can relax it by
>>>>
>>>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>>>> index 5d9eca035d47..bfdbd3fa2d29 100644
>>>> --- a/lib/Kconfig.debug
>>>> +++ b/lib/Kconfig.debug
>>>> @@ -1399,7 +1399,7 @@ config PROVE_LOCKING
>>>>   config PROVE_RAW_LOCK_NESTING
>>>>          bool
>>>>          depends on PROVE_LOCKING
>>>> -       default y
>>>> +       default y if ARCH_SUPPORTS_RT
>>>>          help
>>>>           Enable the raw_spinlock vs. spinlock nesting checks which
>>>> ensure
>>>>           that the lock nesting rules for PREEMPT_RT enabled
>>>> kernels are
>>>>
>>>> Sebastian, what do you think?
>>>>
>>>
>>>     depends on PROVE_LOCKING && ARCH_SUPPORTS_RT
>>>
>>> seems to make more sense to me.
>>
>> That will work too, but that will enforce that arches with no
>> ARCH_SUPPORTS_RT will not be able to enable PROVE_RAW_LOCK_NESTING
>> even if people want to try it out.
>>
>
> No architecture will be able to enable anything because "bool" has no
> string associated with it. As mentioned before, it is all or nothing.
> Otherwise I could just configure "CONFIG_PROVE_RAW_LOCK_NESTING=n"
> for sparc and be done.

Yes, you are right.

Cheers,
Longman