Messages in this thread Patch in this message | | | Subject | Re: [PATCH] LOCKDEP: use depends on LOCKDEP_SUPPORT instead of $ARCH list | From | Randy Dunlap <> | Date | Mon, 24 May 2021 14:41:52 -0700 |
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On 5/24/21 2:31 PM, Randy Dunlap wrote: > On 5/24/21 2:04 PM, Waiman Long wrote: >> 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 > > Right (on the implicit AND). > >> 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. >> > > Ack. I should have done that myself. > >>> >>>> 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. > > Got it. > >>>> 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"): > > and I should have looked at that history too. Thanks. > > Yes, I agree, we can just delete that line... > > I'll send a v2 and copy the author of commit 7d37cb2c912d as well.
Hm, as I review that commit, I have to wonder if the previous 'select' was correct (if we disregard the Kconfig warning). If so, then FRAME_POINTER is still wanted/needed for some arch-es.
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 && !ARC && !X86 <<<<<<<<<<<
>> 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.
-- ~Randy
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