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

Guenter Roeck
2024-11-25T21:25:05Z

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.

Guenter