[PATCH] LOCKDEP: use depends on LOCKDEP_SUPPORT instead of $ARCH list

[Waiman Long]

On 5/17/21 3:11 AM, Ingo Molnar wrote:
> * Randy Dunlap <rdunlap at infradead.org> wrote:
>
>> Both arch/um/ and arch/xtensa/ cause a Kconfig warning for LOCKDEP.
>> These arch-es select LOCKDEP_SUPPORT but they are not listed as one
>> of the arch-es that LOCKDEP depends on.
>>
>> Since (16) arch-es define the Kconfig symbol LOCKDEP_SUPPORT if they
>> intend to have LOCKDEP support, replace the awkward list of
>> arch-es that LOCKDEP depends on with the LOCKDEP_SUPPORT symbol.
>>
>> Fixes this kconfig warning: (for both um and xtensa)
>>
>> WARNING: unmet direct dependencies detected for LOCKDEP
>>    Depends on [n]: DEBUG_KERNEL [=y] && LOCK_DEBUGGING_SUPPORT [=y] && (FRAME_POINTER [=n] || MIPS || PPC || S390 || MICROBLAZE || ARM || ARC || X86)
>>    Selected by [y]:
>>    - PROVE_LOCKING [=y] && DEBUG_KERNEL [=y] && LOCK_DEBUGGING_SUPPORT [=y]
>>    - LOCK_STAT [=y] && DEBUG_KERNEL [=y] && LOCK_DEBUGGING_SUPPORT [=y]
>>    - DEBUG_LOCK_ALLOC [=y] && DEBUG_KERNEL [=y] && LOCK_DEBUGGING_SUPPORT [=y]
>>
>> Signed-off-by: Randy Dunlap <rdunlap at infradead.org>
>> Cc: Peter Zijlstra <peterz at infradead.org>
>> Cc: Ingo Molnar <mingo at redhat.com>
>> Cc: Will Deacon <will at kernel.org>
>> Cc: Waiman Long <longman at redhat.com>
>> Cc: Boqun Feng <boqun.feng at gmail.com>
>> Cc: Chris Zankel <chris at zankel.net>
>> Cc: Max Filippov <jcmvbkbc at gmail.com>
>> Cc: linux-xtensa at linux-xtensa.org
>> Cc: Johannes Berg <johannes at sipsolutions.net>
>> Cc: Jeff Dike <jdike at addtoit.com>
>> Cc: Richard Weinberger <richard at nod.at>
>> Cc: Anton Ivanov <anton.ivanov at cambridgegreys.com>
>> Cc: linux-um at lists.infradead.org
>> ---
>>   lib/Kconfig.debug |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --- linux-next-20210514.orig/lib/Kconfig.debug
>> +++ linux-next-20210514/lib/Kconfig.debug
>> @@ -1383,7 +1383,7 @@ config LOCKDEP
>>   	bool
>>   	depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
>>   	select STACKTRACE
>> -	depends on FRAME_POINTER || MIPS || PPC || S390 || MICROBLAZE || ARM || ARC || X86
>> +	depends on FRAME_POINTER || LOCKDEP_SUPPORT
> Ok - the FRAME_POINTER bit is weird. Are there any architectures that have
> FRAME_POINTER defined but no LOCKDEP_SUPPORT?

LOCK_DEBUGGING_SUPPORT depends on LOCKDEP_SUPPORT. So this patch is 
equivalent to just delete the second depends-on line. Beside LOCKDEP, 
LATENCYTOP also have exactly the same depends-on line.

So isn't FRAME_POINTER used mainly to support STACK_TRACE? However, 
LOCK_DEBUGGING_SUPPORT has already included STACK_TRACE_SUPPORT in its 
dependency. So why there is a FRAME_POINTER dependency?

Cheers,
Longman