[PATCH] fpga: dfl: fme: Fix cpu hotplug issue in performance reporting

[PATCH] fpga: dfl: fme: Fix cpu hotplug issue in performance reporting

[Kajol Jain]

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@intel.com>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
---
 drivers/fpga/dfl-fme-perf.c | 4 ++++
 1 file changed, 4 insertions(+)

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

Re: [PATCH] fpga: dfl: fme: Fix cpu hotplug issue in performance reporting

[kajoljain]

On 6/28/21 3:47 PM, Kajol Jain wrote:
> 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.
> 

Adding stable@vger.kernel.org in cc list as suggested by Moritz Fischer.

Thanks,
Kajol Jain

> Fixes: 724142f8c42a ("fpga: dfl: fme: add performance reporting support")
> Tested-by: Xu Yilun <yilun.xu@intel.com>
> Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
> ---
>  drivers/fpga/dfl-fme-perf.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> ---
> Changelog:
> - 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 */
> +	perf_pmu_migrate_context(&priv->pmu, cpu, target);
> +
>  	return 0;
>  }
>  
> 

Re: [PATCH] fpga: dfl: fme: Fix cpu hotplug issue in performance reporting

[Greg KH]

On Tue, Jun 29, 2021 at 12:45:20PM +0530, kajoljain wrote:
> 
> 
> On 6/28/21 3:47 PM, Kajol Jain wrote:
> > 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.
> > 
> 
> Adding stable@vger.kernel.org in cc list as suggested by Moritz Fischer.


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

Re: [PATCH] fpga: dfl: fme: Fix cpu hotplug issue in performance reporting

[kajoljain]

On 6/29/21 12:57 PM, Greg KH wrote:
> On Tue, Jun 29, 2021 at 12:45:20PM +0530, kajoljain wrote:
>>
>>
>> On 6/28/21 3:47 PM, Kajol Jain wrote:
>>> 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.
>>>
>>
>> Adding stable@vger.kernel.org in cc list as suggested by Moritz Fischer.
> 
> 
> <formletter>
> 
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read:
>     https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.

Thanks Greg for pointing it, I will take care in my next version.

Thanks,
Kajol Jain

> 
> </formletter>
>