From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Nicholas Piggin <npiggin@gmail.com>, peterz@infradead.org
Cc: linux-arch@vger.kernel.org, Will Deacon <will@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state
Date: Wed, 19 Aug 2020 20:39:13 +1000 [thread overview]
Message-ID: <7fadb5ab-9869-396d-ff5d-c0adb6fc0b35@ozlabs.ru> (raw)
In-Reply-To: <1597793862.l8c4pmmzpq.astroid@bobo.none>
On 19/08/2020 09:54, Nicholas Piggin wrote:
> Excerpts from peterz@infradead.org's message of August 19, 2020 1:41 am:
>> On Tue, Aug 18, 2020 at 05:22:33PM +1000, Nicholas Piggin wrote:
>>> Excerpts from peterz@infradead.org's message of August 12, 2020 8:35 pm:
>>>> On Wed, Aug 12, 2020 at 06:18:28PM +1000, Nicholas Piggin wrote:
>>>>> Excerpts from peterz@infradead.org's message of August 7, 2020 9:11 pm:
>>>>>>
>>>>>> What's wrong with something like this?
>>>>>>
>>>>>> AFAICT there's no reason to actually try and add IRQ tracing here, it's
>>>>>> just a hand full of instructions at the most.
>>>>>
>>>>> Because we may want to use that in other places as well, so it would
>>>>> be nice to have tracing.
>>>>>
>>>>> Hmm... also, I thought NMI context was free to call local_irq_save/restore
>>>>> anyway so the bug would still be there in those cases?
>>>>
>>>> NMI code has in_nmi() true, in which case the IRQ tracing is disabled
>>>> (except for x86 which has CONFIG_TRACE_IRQFLAGS_NMI).
>>>>
>>>
>>> That doesn't help. It doesn't fix the lockdep irq state going out of
>>> synch with the actual irq state. The code which triggered this with the
>>> special powerpc irq disable has in_nmi() true as well.
>>
>> Urgh, you're talking about using lockdep_assert_irqs*() from NMI
>> context?
>>
>> If not, I'm afraid I might've lost the plot a little on what exact
>> failure case we're talking about.
>>
>
> Hm, I may have been a bit confused actually. Since your Fix
> TRACE_IRQFLAGS vs NMIs patch it might now work.
>
> I'm worried powerpc disables trace irqs trace_hardirqs_off()
> before nmi_enter() might still be a problem, but not sure
> actually. Alexey did you end up re-testing with Peter's patch
The one above in the thread which replaces powerpc_local_irq_pmu_save()
with
raw_powerpc_local_irq_pmu_save()? It did not compile as there is no
raw_powerpc_local_irq_pmu_save() so I may be missing something here.
I applied the patch on top of the current upstream and replaced
raw_powerpc_local_irq_pmu_save() with raw_local_irq_pmu_save() (which I
think was the intention) but I still see the issue.
> or current upstream?
The upstream 18445bf405cb (13 hours old) also shows the problem. Yours
1/2 still fixes it.
>
> Thanks,
> Nick
>
--
Alexey
next prev parent reply other threads:[~2020-08-19 10:41 UTC|newest]
Thread overview: 28+ 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
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 [this message]
2020-08-19 15:32 ` peterz
2020-08-19 15:39 ` peterz
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