linux-kernel - Re: [PATCH] perf: qcom_l2: fix column exclusion check

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Date:   Tue, 25 Jul 2017 18:01:06 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Neil Leeder <nleeder@...eaurora.org>
Cc:     Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Mark Langsdorf <mlangsdo@...hat.com>,
        Mark Salter <msalter@...hat.com>, Jon Masters <jcm@...hat.com>,
        Timur Tabi <timur@...eaurora.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] perf: qcom_l2: fix column exclusion check

On Mon, Jul 24, 2017 at 05:17:02PM -0400, Neil Leeder wrote:
> The check for column exclusion did not verify that the event being
> checked was an L2 event, and not a software event.
> Software events should not be checked for column exclusion.
> This resulted in a group with both software and L2 events sometimes
> incorrectly rejecting the L2 event for column exclusion and
> not counting it.
> 
> Add a check for PMU type before applying column exclusion logic.
> 
> Signed-off-by: Neil Leeder <nleeder@...eaurora.org>

This looks correct, so:

Acked-by: Mark Rutland <mark.rutland@....com>

Should this have:

Fixes: 21bdbb7102edeaeb ("perf: add qcom l2 cache perf events driver")

... ?

> ---
>  drivers/perf/qcom_l2_pmu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c
> index c259848..b242cce 100644
> --- a/drivers/perf/qcom_l2_pmu.c
> +++ b/drivers/perf/qcom_l2_pmu.c
> @@ -546,6 +546,7 @@ static int l2_cache_event_init(struct perf_event *event)
>  	}
>  
>  	if ((event != event->group_leader) &&
> +	    !is_software_event(event->group_leader) &&
>  	    (L2_EVT_GROUP(event->group_leader->attr.config) ==
>  	     L2_EVT_GROUP(event->attr.config))) {
>  		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
> @@ -558,6 +559,7 @@ static int l2_cache_event_init(struct perf_event *event)
>  	list_for_each_entry(sibling, &event->group_leader->sibling_list,
>  			    group_entry) {
>  		if ((sibling != event) &&
> +		    !is_software_event(sibling) &&
>  		    (L2_EVT_GROUP(sibling->attr.config) ==
>  		     L2_EVT_GROUP(event->attr.config))) {
>  			dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,

It's unfortunate that we duplicate the checks for the leader and
siblings, but that's not a new problem, and we can fix that in a
follow-up patch.

Thanks,
Mark.