linux-kernel - Re: [PATCH] drivers: CCI: fix used_mask init in validate

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Message-ID: <20150409135124.GA9648@leverpostej>
Date:	Thu, 9 Apr 2015 14:51:25 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Mark Salter <msalter@...hat.com>
Cc:	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] drivers: CCI: fix used_mask init in validate_group()

On Wed, Apr 08, 2015 at 07:21:24PM +0100, Mark Salter wrote:
> Currently in validate_group(), there is a static initializer
> for fake_pmu.used_mask which is based on CPU_BITS_NONE but
> the used_mask array size is based on CCI_PMU_MAX_HW_EVENTS.
> CCI_PMU_MAX_HW_EVENTS is not based on NR_CPUS, so CPU_BITS_NONE
> is not correct and will cause a build failure if NR_CPUS
> is set high enough to make CPU_BITS_NONE larger than used_mask.

Whoops. My bad.

> This patch changes the used_mask initialization to be runtime
> based on the actual size of the array.
> 
> Signed-off-by: Mark Salter <msalter@...hat.com>
> ---
>  drivers/bus/arm-cci.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
> index 84fd660..1d83072 100644
> --- a/drivers/bus/arm-cci.c
> +++ b/drivers/bus/arm-cci.c
> @@ -679,13 +679,13 @@ static int
>  validate_group(struct perf_event *event)
>  {
>  	struct perf_event *sibling, *leader = event->group_leader;
> -	struct cci_pmu_hw_events fake_pmu = {
> -		/*
> -		 * Initialise the fake PMU. We only need to populate the
> -		 * used_mask for the purposes of validation.
> -		 */
> -		.used_mask = CPU_BITS_NONE,

Can we not simply change this to:

		.used_mask = { 0 },

That should result in the entire array being zeroed.

Thanks,
Mark.
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