From: Waiman Long <llong@redhat.com>
To: Randy Dunlap <rdunlap@infradead.org>,
Waiman Long <llong@redhat.com>, Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
linux-xtensa@linux-xtensa.org,
Johannes Berg <johannes@sipsolutions.net>,
Jeff Dike <jdike@addtoit.com>,
Richard Weinberger <richard@nod.at>,
Anton Ivanov <anton.ivanov@cambridgegreys.com>,
linux-um@lists.infradead.org
Subject: Re: [PATCH] LOCKDEP: use depends on LOCKDEP_SUPPORT instead of $ARCH list
Date: Mon, 24 May 2021 17:04:55 -0400 [thread overview]
Message-ID: <8a4ee5be-ad5c-ca06-dd1a-aa13ccc94906@redhat.com> (raw)
In-Reply-To: <bfb11ab2-d606-b96e-1979-3bcc3c3adc96@infradead.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 <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
next prev parent reply other threads:[~2021-05-24 21:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 3:44 [PATCH] LOCKDEP: use depends on LOCKDEP_SUPPORT instead of $ARCH list Randy Dunlap
2021-05-17 7:11 ` Ingo Molnar
2021-05-17 14:02 ` Waiman Long
2021-05-23 3:12 ` Randy Dunlap
2021-05-24 19:47 ` Randy Dunlap
2021-05-24 21:04 ` Waiman Long [this message]
2021-05-24 21:31 ` Randy Dunlap
2021-05-24 21:41 ` Randy Dunlap
2021-05-25 0:05 ` Waiman Long
2021-05-25 4:18 ` Randy Dunlap
2021-05-25 14:15 ` Waiman Long
2021-05-23 3:09 ` Randy Dunlap
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