On Mon, 15 Aug 2022 17:28:15 +0800 Yicong Yang <yangyicong@xxxxxxxxxx> 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. > > 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> Looks like progress in a sensible direction to me. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> Kind of unrelated question inline. > > 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"); In this case we have the option to fail probe. Failing to set affinity means we are broken anyway, so perhaps that is cleaner than carrying on. As a side note, I wonder if other drivers could benefit from what I think is a micro optimization to short cut calling the hp handlers when the decision of which CPU is easy... > > err = cpuhp_state_add_instance_nocalls(cpuhp_state_num, > &smmu_pmu->node);
