Re: [PATCH] drivers/perf: Change WARN_ON() to dev_err() on irq_set_affinity() failure

[Yicong Yang]

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@xxxxxxxxxxxxx>
>>
>> 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" which means we passed an invalid input, I think which violiates the "Do not
use these macros when checking for invalid external inputs".

> 
> 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 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.

[*] https://lore.kernel.org/lkml/20220721130116.43366-3-yangyicong@xxxxxxxxxx/

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@xxxxxxxxxxxxxxxxxxx>
>> [https://lore.kernel.org/lkml/YuOi3i0XHV++z1YI@xxxxxxxxx/]
>> Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
>> ---
>>  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
>>
> .
>