Messages in this thread Patch in this message | | | From | Waiman Long <> | Subject | Re: [PATCH] LOCKDEP: use depends on LOCKDEP_SUPPORT instead of $ARCH list | Date | Mon, 24 May 2021 17:04:55 -0400 |
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On 5/24/21 3:47 PM, Randy Dunlap wrote: > On 5/17/21 7:02 AM, Waiman Long wrote: >> On 5/17/21 3:11 AM, Ingo Molnar wrote: >>> * Randy Dunlap <rdunlap@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@infradead.org> >>>> Cc: Peter Zijlstra <peterz@infradead.org> >>>> Cc: Ingo Molnar <mingo@redhat.com> >>>> Cc: Will Deacon <will@kernel.org> >>>> Cc: Waiman Long <longman@redhat.com> >>>> Cc: Boqun Feng <boqun.feng@gmail.com> >>>> Cc: Chris Zankel <chris@zankel.net> >>>> Cc: Max Filippov <jcmvbkbc@gmail.com> >>>> Cc: linux-xtensa@linux-xtensa.org >>>> Cc: Johannes Berg <johannes@sipsolutions.net> >>>> Cc: Jeff Dike <jdike@addtoit.com> >>>> Cc: Richard Weinberger <richard@nod.at> >>>> Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com> >>>> Cc: linux-um@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. > Yes, if we disregard the FRAME_POINTER part.
My understanding is that the 2 depends-on statements have an implicit AND. So it is like
DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT && (FRAME_POINTER || LOCKDEP_SUPPORT). LOCK_DEBUGGING_SUPPORT is true means the (FRAME_POINTER || LOCKDEP_SUPPORT) will always be true. FRAME_POINTER is true doesn't mean the other dependencies are true. That is why I said it is equivalent to just "DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT". IOW, FRAME_POINTER will play no part here.
> >> Beside LOCKDEP, LATENCYTOP also have exactly the same depends-on line. > True, but I don't get any implication that the same patch applies there. > Do you? It is just an observation that I stumble on. It is not related to your patch. >> 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? > FRAME_POINTER is one way but it does not seem to be required > for STACKTRACE_SUPPORT. > > Do you have any patch suggestions?
Is it possible to just get rid of the 2nd depends-on statement?
The 2nd depends-on line was introduced by commit 7d37cb2c912d ("lib: fix kconfig dependency on ARCH_WANT_FRAME_POINTER"):
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 2779c29d9981..417c3d3e521b 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1363,7 +1363,7 @@ config LOCKDEP bool depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT select STACKTRACE - select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && + depends on FRAME_POINTER || MIPS || PPC || S390 || MICROBLAZE || ARM || select KALLSYMS select KALLSYMS_ALL
Since STACKTRACE is selected by lockdep, maybe we can just remove the 2nd depends-on line to see if anyone complain. Cheers, Longman
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