linux-kernel - Re: [PATCH 2/3] perf/arm-cci: Remove pointless PMU disabling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20180511143814.i4iorhlhyxslgkzn@lakrids.cambridge.arm.com>
Date:   Fri, 11 May 2018 15:38:14 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     will.deacon@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, pawel.moll@....com,
        suzuki.poulose@....com
Subject: Re: [PATCH 2/3] perf/arm-cci: Remove pointless PMU disabling

On Fri, May 11, 2018 at 03:29:13PM +0100, Robin Murphy wrote:
> The CCI PMU driver bears some legacy remnants of the arm_pmu framework
> from when it was split in c6f85cb4305b ("bus: cci: move away from
> arm_pmu framework"). In particular this perf_pmu_{dis,en}able() dance
> around pmu->add which was fixed for arm_pmu in a9e469d1c89b
> ("drivers/perf: arm_pmu: remove pointless PMU disabling").
> 
> For the exact same reasons (i.e. perf core already does this around the
> call anyway), give cci_pmu_add() the exact same change, which also
> prevents having to export those core functions to build it as a module.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>

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

Mark.

> ---
>  drivers/perf/arm-cci.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/perf/arm-cci.c b/drivers/perf/arm-cci.c
> index 53c774b20563..7029d8fe8f44 100644
> --- a/drivers/perf/arm-cci.c
> +++ b/drivers/perf/arm-cci.c
> @@ -1184,16 +1184,11 @@ static int cci_pmu_add(struct perf_event *event, int flags)
>  	struct cci_pmu_hw_events *hw_events = &cci_pmu->hw_events;
>  	struct hw_perf_event *hwc = &event->hw;
>  	int idx;
> -	int err = 0;
> -
> -	perf_pmu_disable(event->pmu);
>  
>  	/* If we don't have a space for the counter then finish early. */
>  	idx = pmu_get_event_idx(hw_events, event);
> -	if (idx < 0) {
> -		err = idx;
> -		goto out;
> -	}
> +	if (idx < 0)
> +		return idx;
>  
>  	event->hw.idx = idx;
>  	hw_events->events[idx] = event;
> @@ -1205,9 +1200,7 @@ static int cci_pmu_add(struct perf_event *event, int flags)
>  	/* Propagate our changes to the userspace mapping. */
>  	perf_event_update_userpage(event);
>  
> -out:
> -	perf_pmu_enable(event->pmu);
> -	return err;
> +	return 0;
>  }
>  
>  static void cci_pmu_del(struct perf_event *event, int flags)
> -- 
> 2.17.0.dirty
>