On 2022/8/15 17:39, Jonathan Cameron wrote: > 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. > Thanks for the quick review! replies below. >> > > >> 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. > This patch only switch the way on error notification with no functional change intended. So if we need to change the behaviour here it should be in a separate patch. Indeed I'm not sure it's necessary to fail probe here since we can use the pmu if it fails here. > 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... > It seems sensible to me but may differ in differenct pmu drivers since they may need the hp handlers called. Needs more check. Thanks. >> >> err = cpuhp_state_add_instance_nocalls(cpuhp_state_num, >> &smmu_pmu->node); > . >
