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Date:   Tue, 16 Aug 2022 11:26:28 +0100
From:   Mark Rutland <mark.rutland@arm.com>
To:     Yicong Yang <yangyicong@huawei.com>
Cc:     yangyicong@hisilicon.com, will@kernel.org, Frank.li@nxp.com,
        shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de,
        festevam@gmail.com, linux-imx@nxp.com, zhangshaokun@hisilicon.com,
        agross@kernel.org, bjorn.andersson@linaro.org,
        konrad.dybcio@somainline.org, khuong@os.amperecomputing.com,
        john.garry@huawei.com, jonathan.cameron@huawei.com,
        gregkh@linuxfoundation.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] drivers/perf: Change WARN_ON() to dev_err() on
 irq_set_affinity() failure
Message-ID: <Yvtw1DAhYBgsuTTV@FVFF77S0Q05N>
References: <20220815092815.11597-1-yangyicong@huawei.com>
 <YvotEZigh0+I/RIb@FVFF77S0Q05N>
 <2e0c3a14-d308-dfd2-debe-8a52a3db47cc@huawei.com>
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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@hisilicon.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.

Thanks,
Mark.

> 
> [*] 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@linuxfoundation.org>
> >> [https://lore.kernel.org/lkml/YuOi3i0XHV++z1YI@kroah.com/]
> >> Signed-off-by: Yicong Yang <yangyicong@hisilicon.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
> >>
> > .
> >