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

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Message-ID: <DM6PR11MB38197304C3BC02672304201A85159@DM6PR11MB3819.namprd11.prod.outlook.com>
Date:   Mon, 12 Jul 2021 02:27:24 +0000
From:   "Wu, Hao" <hao.wu@...el.com>
To:     Kajol Jain <kjain@...ux.ibm.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

> 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>

Thanks
Hao

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