Message-ID: <5c642a7d-85d5-2a6c-7455-a0585590a7fb@gmail.com>
Date:   Tue, 16 Aug 2022 23:20:09 +0800
From:   Yicong Yang <yangyccccc@...il.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     yangyicong@...ilicon.com, will@...nel.org, Frank.li@....com,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com, zhangshaokun@...ilicon.com,
        agross@...nel.org, bjorn.andersson@...aro.org,
        konrad.dybcio@...ainline.org, khuong@...amperecomputing.com,
        john.garry@...wei.com, jonathan.cameron@...wei.com,
        gregkh@...uxfoundation.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Yicong Yang <yangyicong@...wei.com>
Subject: Re: [PATCH] drivers/perf: Change WARN_ON() to dev_err() on
 irq_set_affinity() failure

On 8/16/2022 6:26 PM, Mark Rutland wrote:
> On Tue, Aug 16, 2022 at 03:37:29PM +0800, Yicong Yang wrote:
>> On 2022/8/15 19:25, Mark Rutland wrote:
>>> On Mon, Aug 15, 2022 at 05:28:15PM +0800, Yicong Yang wrote:
>>>> From: Yicong Yang <yangyicong@...ilicon.com>
>>>>
>>>> The WARN_ON() on irq_set_affinity() failure is misused according to the [1]
>>>> and may crash people's box unintentionally. This may also be redundant since
>>>> in the failure case we may also trigger the WARN and dump the stack in the
>>>> perf core[2] for a second time.
>>>
>>> In what way do you think are these misused? I can't immediately see what you
>>> think applies from [1].
>>
>> As commented by irq_set_affinity() it "Fails if cpumask does not contain an online
>>  CPU" 
> 
> In all of the cases below we've chosen an online CPU. So the only way this can
> happen is if there is a bug in the code, in which case a WARN_ON() is
> appropriate. Also, there are *other* reasons irq_set_affinity() can fail.
> 
>> which means we passed an invalid input, I think which violiates the "Do not
>> use these macros when checking for invalid external inputs".
> 
> There is no external input here. The chosen CPU didn't come from userspace or
> an external source; we chose it ourselves based on kernel internal data (e.g.
> cpu_online_mask).
> 
> So that does not apply here.
> 
>>> In perf we rely upon interrupt affinity to enforce serialization in a few
>>> places, so if we fail to set the interrupt affinity there are a number of
>>> things which could go wrong (e.g. memory corruption, and all the fun that could
>>> result from that). We use WARN_ON() to catch that early.
>>
>> If we'd like to catch this failure information early maybe a dev_err() should be
>> enough to indicate this.
> 
> I don't see why it is necessary to change to dev_err().
> 
>>> I can't immediately see how [2] is relevant, since that's in the context of an
>>> IPI handler, and this patch affects the affinity of the PMU HW IRQ handler.
>>
>> I think it's relevant (please correct me) as when I debug another pmu driver using
>> MSI interrupt[*], I found I'll trigger the WARN() in [2] if the interrupt is not
>> bind to the CPU which start trace. So I think it's required to handle the interrupt
>> on the same CPU start the trace otherwise the "context" is mismatched.
> 
> Sorry, I had confused event_function_local() with event_function().
> 
> I still think we want to keep the WARN_ON() here since before we get to
> event_function_local() we may do other things in the IRQ handler.
> 

ok. Another point of this patch is to avoid panic and reboot on WARN() (pointed by Greg
to not crash people's box), is it intended here? If not but we still want a callstack in
these places, does it make sense to use dev_err() + dump_stack() instead?

Thanks.

> 
>>
>> [*] https://lore.kernel.org/lkml/20220721130116.43366-3-yangyicong@huawei.com/
>>
>> Thanks.
>>
>>> Thanks,
>>> Mark.
>>>
>>>>
>>>> So change the WARN_ON() to dev_err() to just print the failure message.
>>>>
>>>> [1] https://github.com/torvalds/linux/blob/master/include/asm-generic/bug.h#L74
>>>> [2] https://github.com/torvalds/linux/blob/master/kernel/events/core.c#L313
>>>>
>>>> Suggested-by: Greg KH <gregkh@...uxfoundation.org>
>>>> [https://lore.kernel.org/lkml/YuOi3i0XHV++z1YI@kroah.com/]
>>>> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
>>>> ---
>>>>  drivers/perf/arm-ccn.c                   | 5 +++--
>>>>  drivers/perf/arm_dmc620_pmu.c            | 3 ++-
>>>>  drivers/perf/arm_smmuv3_pmu.c            | 6 ++++--
>>>>  drivers/perf/fsl_imx8_ddr_perf.c         | 3 ++-
>>>>  drivers/perf/hisilicon/hisi_pcie_pmu.c   | 6 ++++--
>>>>  drivers/perf/hisilicon/hisi_uncore_pmu.c | 6 ++++--
>>>>  drivers/perf/qcom_l2_pmu.c               | 8 ++++++--
>>>>  drivers/perf/xgene_pmu.c                 | 6 ++++--
>>>>  8 files changed, 29 insertions(+), 14 deletions(-)
>>>>
>>>> diff --git a/drivers/perf/arm-ccn.c b/drivers/perf/arm-ccn.c
>>>> index 728d13d8e98a..83abd909ba49 100644
>>>> --- a/drivers/perf/arm-ccn.c
>>>> +++ b/drivers/perf/arm-ccn.c
>>>> @@ -1210,8 +1210,9 @@ static int arm_ccn_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  		return 0;
>>>>  	perf_pmu_migrate_context(&dt->pmu, cpu, target);
>>>>  	dt->cpu = target;
>>>> -	if (ccn->irq)
>>>> -		WARN_ON(irq_set_affinity(ccn->irq, cpumask_of(dt->cpu)));
>>>> +	if (ccn->irq && irq_set_affinity(ccn->irq, cpumask_of(dt->cpu)))
>>>> +		dev_err(ccn->dev, "Failed to set interrupt affinity\n");
>>>> +
>>>>  	return 0;
>>>>  }
>>>>  
>>>> diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c
>>>> index 280a6ae3e27c..b59d3d9eb779 100644
>>>> --- a/drivers/perf/arm_dmc620_pmu.c
>>>> +++ b/drivers/perf/arm_dmc620_pmu.c
>>>> @@ -621,7 +621,8 @@ static int dmc620_pmu_cpu_teardown(unsigned int cpu,
>>>>  		perf_pmu_migrate_context(&dmc620_pmu->pmu, irq->cpu, target);
>>>>  	mutex_unlock(&dmc620_pmu_irqs_lock);
>>>>  
>>>> -	WARN_ON(irq_set_affinity(irq->irq_num, cpumask_of(target)));
>>>> +	if (irq_set_affinity(irq->irq_num, cpumask_of(target)))
>>>> +		dev_err(dmc620_pmu->pmu.dev, "Failed to set interrupt affinity\n");
>>>>  	irq->cpu = target;
>>>>  
>>>>  	return 0;
>>>> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
>>>> index 00d4c45a8017..05e1b3e274d7 100644
>>>> --- a/drivers/perf/arm_smmuv3_pmu.c
>>>> +++ b/drivers/perf/arm_smmuv3_pmu.c
>>>> @@ -646,7 +646,8 @@ static int smmu_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  
>>>>  	perf_pmu_migrate_context(&smmu_pmu->pmu, cpu, target);
>>>>  	smmu_pmu->on_cpu = target;
>>>> -	WARN_ON(irq_set_affinity(smmu_pmu->irq, cpumask_of(target)));
>>>> +	if (irq_set_affinity(smmu_pmu->irq, cpumask_of(target)))
>>>> +		dev_err(smmu_pmu->dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> @@ -892,7 +893,8 @@ static int smmu_pmu_probe(struct platform_device *pdev)
>>>>  
>>>>  	/* Pick one CPU to be the preferred one to use */
>>>>  	smmu_pmu->on_cpu = raw_smp_processor_id();
>>>> -	WARN_ON(irq_set_affinity(smmu_pmu->irq, cpumask_of(smmu_pmu->on_cpu)));
>>>> +	if (irq_set_affinity(smmu_pmu->irq, cpumask_of(smmu_pmu->on_cpu)))
>>>> +		dev_err(dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	err = cpuhp_state_add_instance_nocalls(cpuhp_state_num,
>>>>  					       &smmu_pmu->node);
>>>> diff --git a/drivers/perf/fsl_imx8_ddr_perf.c b/drivers/perf/fsl_imx8_ddr_perf.c
>>>> index 8e058e08fe81..c44192e2d9db 100644
>>>> --- a/drivers/perf/fsl_imx8_ddr_perf.c
>>>> +++ b/drivers/perf/fsl_imx8_ddr_perf.c
>>>> @@ -671,7 +671,8 @@ static int ddr_perf_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  	perf_pmu_migrate_context(&pmu->pmu, cpu, target);
>>>>  	pmu->cpu = target;
>>>>  
>>>> -	WARN_ON(irq_set_affinity(pmu->irq, cpumask_of(pmu->cpu)));
>>>> +	if (irq_set_affinity(pmu->irq, cpumask_of(pmu->cpu)))
>>>> +		dev_err(pmu->dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> diff --git a/drivers/perf/hisilicon/hisi_pcie_pmu.c b/drivers/perf/hisilicon/hisi_pcie_pmu.c
>>>> index 21771708597d..90aed9e51396 100644
>>>> --- a/drivers/perf/hisilicon/hisi_pcie_pmu.c
>>>> +++ b/drivers/perf/hisilicon/hisi_pcie_pmu.c
>>>> @@ -655,7 +655,8 @@ static int hisi_pcie_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  
>>>>  	if (pcie_pmu->on_cpu == -1) {
>>>>  		pcie_pmu->on_cpu = cpu;
>>>> -		WARN_ON(irq_set_affinity(pcie_pmu->irq, cpumask_of(cpu)));
>>>> +		if (irq_set_affinity(pcie_pmu->irq, cpumask_of(cpu)))
>>>> +			pci_err(pcie_pmu->pdev, "Failed to set interrupt affinity\n");
>>>>  	}
>>>>  
>>>>  	return 0;
>>>> @@ -681,7 +682,8 @@ static int hisi_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  	perf_pmu_migrate_context(&pcie_pmu->pmu, cpu, target);
>>>>  	/* Use this CPU for event counting */
>>>>  	pcie_pmu->on_cpu = target;
>>>> -	WARN_ON(irq_set_affinity(pcie_pmu->irq, cpumask_of(target)));
>>>> +	if (irq_set_affinity(pcie_pmu->irq, cpumask_of(target)))
>>>> +		pci_err(pcie_pmu->pdev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> diff --git a/drivers/perf/hisilicon/hisi_uncore_pmu.c b/drivers/perf/hisilicon/hisi_uncore_pmu.c
>>>> index fbc8a93d5eac..74397b5ec889 100644
>>>> --- a/drivers/perf/hisilicon/hisi_uncore_pmu.c
>>>> +++ b/drivers/perf/hisilicon/hisi_uncore_pmu.c
>>>> @@ -492,7 +492,8 @@ int hisi_uncore_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  	hisi_pmu->on_cpu = cpu;
>>>>  
>>>>  	/* Overflow interrupt also should use the same CPU */
>>>> -	WARN_ON(irq_set_affinity(hisi_pmu->irq, cpumask_of(cpu)));
>>>> +	if (irq_set_affinity(hisi_pmu->irq, cpumask_of(cpu)))
>>>> +		dev_err(hisi_pmu->dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> @@ -525,7 +526,8 @@ int hisi_uncore_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  	perf_pmu_migrate_context(&hisi_pmu->pmu, cpu, target);
>>>>  	/* Use this CPU for event counting */
>>>>  	hisi_pmu->on_cpu = target;
>>>> -	WARN_ON(irq_set_affinity(hisi_pmu->irq, cpumask_of(target)));
>>>> +	if (irq_set_affinity(hisi_pmu->irq, cpumask_of(target)))
>>>> +		dev_err(hisi_pmu->dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c
>>>> index 30234c261b05..c6fe01c7e637 100644
>>>> --- a/drivers/perf/qcom_l2_pmu.c
>>>> +++ b/drivers/perf/qcom_l2_pmu.c
>>>> @@ -793,7 +793,9 @@ static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  	cpumask_set_cpu(cpu, &l2cache_pmu->cpumask);
>>>>  	cluster_pmu_reset();
>>>>  
>>>> -	WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(cpu)));
>>>> +	if (irq_set_affinity(cluster->irq, cpumask_of(cpu)))
>>>> +		dev_err(&l2cache_pmu->pdev->dev,
>>>> +			"Failed to set interrupt affinity\n");
>>>>  	enable_irq(cluster->irq);
>>>>  
>>>>  	return 0;
>>>> @@ -831,7 +833,9 @@ static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  	perf_pmu_migrate_context(&l2cache_pmu->pmu, cpu, target);
>>>>  	cluster->on_cpu = target;
>>>>  	cpumask_set_cpu(target, &l2cache_pmu->cpumask);
>>>> -	WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(target)));
>>>> +	if (irq_set_affinity(cluster->irq, cpumask_of(target)))
>>>> +		dev_err(&l2cache_pmu->pdev->dev,
>>>> +			"Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> diff --git a/drivers/perf/xgene_pmu.c b/drivers/perf/xgene_pmu.c
>>>> index 0c32dffc7ede..f31e678fdb69 100644
>>>> --- a/drivers/perf/xgene_pmu.c
>>>> +++ b/drivers/perf/xgene_pmu.c
>>>> @@ -1790,7 +1790,8 @@ static int xgene_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  		cpumask_set_cpu(cpu, &xgene_pmu->cpu);
>>>>  
>>>>  	/* Overflow interrupt also should use the same CPU */
>>>> -	WARN_ON(irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu));
>>>> +	if (irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu))
>>>> +		dev_err(xgene_pmu->dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> @@ -1823,7 +1824,8 @@ static int xgene_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
>>>>  
>>>>  	cpumask_set_cpu(target, &xgene_pmu->cpu);
>>>>  	/* Overflow interrupt also should use the same CPU */
>>>> -	WARN_ON(irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu));
>>>> +	if (irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu))
>>>> +		dev_err(xgene_pmu->dev, "Failed to set interrupt affinity\n");
>>>>  
>>>>  	return 0;
>>>>  }
>>>> -- 
>>>> 2.24.0
>>>>
>>> .
>>>

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