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@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" 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@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 > >> > > . > >
