Re: [PATCH] perf/smmuv3: Remove the leftover put_cpu() in error path

From: Hanjun Guo
Date: Tue Dec 10 2019 - 08:55:45 EST


On 2019/12/10 21:24, Will Deacon wrote:
> On Tue, Dec 10, 2019 at 06:46:24PM +0800, Hanjun Guo wrote:
>> In smmu_pmu_probe(), there is put_cpu() in the error path,
>> which is wrong because we use raw_smp_processor_id() to
>> get the cpu ID, not get_cpu(), remove it.
>>
>> Signed-off-by: Hanjun Guo <guohanjun@xxxxxxxxxx>
>> ---
>> drivers/perf/arm_smmuv3_pmu.c | 1 -
>> 1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
>> index 773128f..fd1d46a 100644
>> --- a/drivers/perf/arm_smmuv3_pmu.c
>> +++ b/drivers/perf/arm_smmuv3_pmu.c
>> @@ -834,7 +834,6 @@ static int smmu_pmu_probe(struct platform_device *pdev)
>> out_unregister:
>> cpuhp_state_remove_instance_nocalls(cpuhp_state_num, &smmu_pmu->node);
>> out_cpuhp_err:
>> - put_cpu();
>> return err;
>
> Can we kill 'out_cpuhp_err' altogether then and just return err if we fail
> to add the hotplug instance?

Makes sense, but I think we can go further to kill both 'out_cpuhp_err' and
'out_register' as below [1], what do you think?

Thanks
Hanjun

[1]:
diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
index fd1d46a..a5adaba 100644
--- a/drivers/perf/arm_smmuv3_pmu.c
+++ b/drivers/perf/arm_smmuv3_pmu.c
@@ -814,14 +814,15 @@ static int smmu_pmu_probe(struct platform_device *pdev)
if (err) {
dev_err(dev, "Error %d registering hotplug, PMU @%pa\n",
err, &res_0->start);
- goto out_cpuhp_err;
+ return err;
}

err = perf_pmu_register(&smmu_pmu->pmu, name, -1);
if (err) {
+ cpuhp_state_remove_instance_nocalls(cpuhp_state_num, &smmu_pmu->node);
dev_err(dev, "Error %d registering PMU @%pa\n",
err, &res_0->start);
- goto out_unregister;
+ return err;
}

dev_info(dev, "Registered PMU @ %pa using %d counters with %s filter settings\n",
@@ -830,11 +831,6 @@ static int smmu_pmu_probe(struct platform_device *pdev)
"Individual");

return 0;
-
-out_unregister:
- cpuhp_state_remove_instance_nocalls(cpuhp_state_num, &smmu_pmu->node);
-out_cpuhp_err:
- return err;
}

static int smmu_pmu_remove(struct platform_device *pdev)