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Mon, 24 May 2021 14:04:58 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id f17sm5139085qto.68.2021.05.24.14.04.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 May 2021 14:04:57 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH] LOCKDEP: use depends on LOCKDEP_SUPPORT instead of $ARCH list To: Randy Dunlap , Waiman Long , Ingo Molnar Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Johannes Berg , Jeff Dike , Richard Weinberger , Anton Ivanov , linux-um@lists.infradead.org References: <20210517034430.9569-1-rdunlap@infradead.org> <1284b997-b9da-769f-2d36-4d4232c7df88@redhat.com> Message-ID: <8a4ee5be-ad5c-ca06-dd1a-aa13ccc94906@redhat.com> Date: Mon, 24 May 2021 17:04:55 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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 >>>> Cc: Peter Zijlstra >>>> Cc: Ingo Molnar >>>> Cc: Will Deacon >>>> Cc: Waiman Long >>>> Cc: Boqun Feng >>>> Cc: Chris Zankel >>>> Cc: Max Filippov >>>> Cc: linux-xtensa@linux-xtensa.org >>>> Cc: Johannes Berg >>>> Cc: Jeff Dike >>>> Cc: Richard Weinberger >>>> Cc: Anton Ivanov >>>> 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