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

Waiman Long
2024-11-25T20:54:54Z

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?

Cheers,
Longman

> Guenter
>