From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Nicholas Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@redhat.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state
Date: Sun, 26 Jul 2020 17:40:10 +1000 [thread overview]
Message-ID: <600a08a0-4b33-03a5-4749-bda8fa1e572d@ozlabs.ru> (raw)
In-Reply-To: <1595568105.4eodjnxzwp.astroid@bobo.none>
On 24/07/2020 15:59, Nicholas Piggin wrote:
> Excerpts from Alexey Kardashevskiy's message of July 24, 2020 2:16 pm:
>>
>>
>> On 23/07/2020 23:11, Nicholas Piggin wrote:
>>> Excerpts from Peter Zijlstra's message of July 23, 2020 9:40 pm:
>>>> On Thu, Jul 23, 2020 at 08:56:14PM +1000, Nicholas Piggin wrote:
>>>>
>>>>> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
>>>>> index 3a0db7b0b46e..35060be09073 100644
>>>>> --- a/arch/powerpc/include/asm/hw_irq.h
>>>>> +++ b/arch/powerpc/include/asm/hw_irq.h
>>>>> @@ -200,17 +200,14 @@ static inline bool arch_irqs_disabled(void)
>>>>> #define powerpc_local_irq_pmu_save(flags) \
>>>>> do { \
>>>>> raw_local_irq_pmu_save(flags); \
>>>>> - trace_hardirqs_off(); \
>>>>> + if (!raw_irqs_disabled_flags(flags)) \
>>>>> + trace_hardirqs_off(); \
>>>>> } while(0)
>>>>> #define powerpc_local_irq_pmu_restore(flags) \
>>>>> do { \
>>>>> - if (raw_irqs_disabled_flags(flags)) { \
>>>>> - raw_local_irq_pmu_restore(flags); \
>>>>> - trace_hardirqs_off(); \
>>>>> - } else { \
>>>>> + if (!raw_irqs_disabled_flags(flags)) \
>>>>> trace_hardirqs_on(); \
>>>>> - raw_local_irq_pmu_restore(flags); \
>>>>> - } \
>>>>> + raw_local_irq_pmu_restore(flags); \
>>>>> } while(0)
>>>>
>>>> You shouldn't be calling lockdep from NMI context!
>>>
>>> After this patch it doesn't.
>>>
>>> trace_hardirqs_on/off implementation appears to expect to be called in NMI
>>> context though, for some reason.
>>>
>>>> That is, I recently
>>>> added suport for that on x86:
>>>>
>>>> https://lkml.kernel.org/r/20200623083721.155449112@infradead.org
>>>> https://lkml.kernel.org/r/20200623083721.216740948@infradead.org
>>>>
>>>> But you need to be very careful on how you order things, as you can see
>>>> the above relies on preempt_count() already having been incremented with
>>>> NMI_MASK.
>>>
>>> Hmm. My patch seems simpler.
>>
>> And your patches fix my error while Peter's do not:
>>
>>
>> IRQs not enabled as expected
>> WARNING: CPU: 0 PID: 1377 at /home/aik/p/kernel/kernel/softirq.c:169
>> __local_bh_enable_ip+0x118/0x190
>
> I think they would have needed some powerpc bits as well.
True, there is quite a lot to repeat of what x86 does, I was in a hurry
and did not think it through :)
> But I don't
> see a reason we can't merge my patches, at least they fix this case and
> don't seem to make things worse in any way.
True. Or we could keep these lockdep_stats::redundant_softirqs_on/etc
and make powerpc_local_irq_pmu_restore()/local_irq_restore() call
trace_hardirqs_on() always and let lockdep do reference counting, may be?
--
Alexey
next prev parent reply other threads:[~2020-07-26 7:40 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 10:56 [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Nicholas Piggin
2020-07-23 10:56 ` [PATCH 2/2] lockdep: warn on redundant or incorrect irq state changes Nicholas Piggin
2020-07-24 2:57 ` kernel test robot
2020-08-04 10:00 ` Alexey Kardashevskiy
2020-07-23 11:40 ` [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Peter Zijlstra
2020-07-23 13:11 ` Nicholas Piggin
2020-07-23 14:59 ` Peter Zijlstra
2020-07-23 16:20 ` Nicholas Piggin
2020-07-24 4:16 ` Alexey Kardashevskiy
2020-07-24 5:59 ` Nicholas Piggin
2020-07-26 7:40 ` Alexey Kardashevskiy [this message]
2020-07-24 6:16 ` Athira Rajeev
2020-07-24 2:19 ` kernel test robot
2020-07-24 3:15 ` kernel test robot
2020-07-25 20:26 ` Peter Zijlstra
2020-07-26 4:14 ` Nicholas Piggin
2020-07-26 11:59 ` peterz
2020-07-26 12:11 ` peterz
2020-07-28 11:22 ` Nicholas Piggin
2020-08-07 11:11 ` peterz
2020-08-12 8:18 ` Nicholas Piggin
2020-08-12 10:35 ` peterz
2020-08-18 7:22 ` Nicholas Piggin
2020-08-18 15:41 ` peterz
2020-08-18 23:54 ` Nicholas Piggin
2020-08-19 10:39 ` Alexey Kardashevskiy
2020-08-19 15:32 ` peterz
2020-08-19 15:39 ` peterz
2020-08-27 7:54 ` [tip: locking/core] lockdep: Only trace IRQ edges tip-bot2 for Nicholas Piggin
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