linux-kernel - Re: [PATCH v2] fpga: dfl: fme: Fix cpu hotplug issue in performance reporting

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Message-ID: <962ef143-024c-71e3-b781-b027154a12bd@linux.ibm.com>
Date:   Tue, 13 Jul 2021 13:07:52 +0530
From:   kajoljain <kjain@...ux.ibm.com>
To:     "Wu, Hao" <hao.wu@...el.com>, "will@...nel.org" <will@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "Xu, Yilun" <yilun.xu@...el.com>
Cc:     "trix@...hat.com" <trix@...hat.com>,
        "mdf@...nel.org" <mdf@...nel.org>,
        "linux-fpga@...r.kernel.org" <linux-fpga@...r.kernel.org>,
        "maddy@...ux.ibm.com" <maddy@...ux.ibm.com>,
        "atrajeev@...ux.vnet.ibm.com" <atrajeev@...ux.vnet.ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "rnsastry@...ux.ibm.com" <rnsastry@...ux.ibm.com>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] fpga: dfl: fme: Fix cpu hotplug issue in performance
 reporting



On 7/12/21 7:57 AM, Wu, Hao wrote:
>> Subject: [PATCH v2] fpga: dfl: fme: Fix cpu hotplug issue in performance
>> reporting
>>
>> The performance reporting driver added cpu hotplug
>> feature but it didn't add pmu migration call in cpu
>> offline function.
>> This can create an issue incase the current designated
>> cpu being used to collect fme pmu data got offline,
>> as based on current code we are not migrating fme pmu to
>> new target cpu. Because of that perf will still try to
>> fetch data from that offline cpu and hence we will not
>> get counter data.
>>
>> Patch fixed this issue by adding pmu_migrate_context call
>> in fme_perf_offline_cpu function.
>>
>> Fixes: 724142f8c42a ("fpga: dfl: fme: add performance reporting support")
>> Tested-by: Xu Yilun <yilun.xu@...el.com>
>> Signed-off-by: Kajol Jain <kjain@...ux.ibm.com>
> 
> Thanks for this fixing! And thanks Yilun for the verification too. : )
> 
>> Cc: stable@...r.kernel.org
>> ---
>>  drivers/fpga/dfl-fme-perf.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> ---
>> Changelog:
>> v1 -> v2:
>> - Add stable@...r.kernel.org in cc list
>>
>> RFC -> PATCH v1
>> - Remove RFC tag
>> - Did nits changes on subject and commit message as suggested by Xu Yilun
>> - Added Tested-by tag
>> - Link to rfc patch: https://lkml.org/lkml/2021/6/28/112
>> ---
>> diff --git a/drivers/fpga/dfl-fme-perf.c b/drivers/fpga/dfl-fme-perf.c
>> index 4299145ef347..b9a54583e505 100644
>> --- a/drivers/fpga/dfl-fme-perf.c
>> +++ b/drivers/fpga/dfl-fme-perf.c
>> @@ -953,6 +953,10 @@ static int fme_perf_offline_cpu(unsigned int cpu, struct
>> hlist_node *node)
>>  		return 0;
>>
>>  	priv->cpu = target;
>> +
>> +	/* Migrate fme_perf pmu events to the new target cpu */
> 
> Only one minor item, this line is not needed. : )
> 
> After remove it, 
> Acked-by: Wu Hao <hao.wu@...el.com>

Hi Wu Hao,
   Sure I will remove this comment and send new patch.

Thanks,
Kajol Jain

> 
> Thanks
> Hao
> 
>> +	perf_pmu_migrate_context(&priv->pmu, cpu, target);
>> +
>>  	return 0;
>>  }
>>
>> --
>> 2.31.1
>