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Subject: Re: [PATCH] perf/smmuv3: Remove the leftover put_cpu() in error path
To:     Will Deacon <will@kernel.org>
CC:     Mark Rutland <mark.rutland@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <1575974784-55046-1-git-send-email-guohanjun@huawei.com>
 <20191210132458.GA19183@willie-the-truck>
From:   Hanjun Guo <guohanjun@huawei.com>
Message-ID: <d251a136-2722-93ba-1bea-0000bf257db2@huawei.com>
Date:   Tue, 10 Dec 2019 21:55:28 +0800
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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@huawei.com>
>> ---
>>  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)