linux-kernel - Re: [PATCH v2] perf: xgene: Add CPU hotplug support

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Message-ID: <20181002114627.omsungd77lfmbqfj@lakrids.cambridge.arm.com>
Date:   Tue, 2 Oct 2018 12:46:27 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Hoan Tran <hoan.tran@...erecomputing.com>
Cc:     Will Deacon <will.deacon@....com>,
        Tai Nguyen <ttnguyen@...erecomputing.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Open Source Submission <patches@...erecomputing.com>
Subject: Re: [PATCH v2] perf: xgene: Add CPU hotplug support

Hi Hoan,

On Wed, Sep 19, 2018 at 06:44:30PM +0000, Hoan Tran wrote:
> This patch adds CPU hotplug support where the PMU migrates the context to
> another online CPU when its CPU is offline.
> 
> It fixes the below issue where the user does offline the CPU which is assigned
> to this PMU.
> 
> Assuming, CPU0 is assigned for this PMU. When the user does offline CPU0
> [root@(none) ~]# echo 0 > /sys/devices/system/cpu/cpu0/online
> This PMU does not work anymore and shows the below error.
> [root@(none) ~]# perf stat -a -e l3c0/cycle-count/,l3c0/write/ sleep 1
> Error:
> The sys_perf_event_open() syscall returned with 19 (No such device) for event (l3c0/cycle-count/).
> /bin/dmesg may provide additional information.
> No CONFIG_PERF_EVENTS=y kernel support configured?
> 
> With this patch, when CPU0 is offline, PMU migrates to another online CPU and
> works on that CPU.
> 
> Signed-off-by: Hoan Tran <hoan.tran@...erecomputing.com>
> ---
> v2:
>  * Remove the cpuhp instance when unregistering the PMU

Unfortunately, this has come through whitespae-damaged, with a
disclaimer in the footer.

Could you please resend with those two details fixed?

Thanks,
Mark.