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    SubjectRe: [PATCH] drivers/perf: Change WARN_ON() to dev_err() on irq_set_affinity() failure
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    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" 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@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
    >>
    > .
    >

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