linux-kernel - Re: [PATCH v2 1/2] net/mlx4_core: clean up cq_res_start_move

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Message-ID: <20140116094639.6fe72bcf@jpm-OptiPlex-GX620>
Date:	Thu, 16 Jan 2014 09:46:39 +0200
From:	Jack Morgenstein <jackm@....mellanox.co.il>
To:	Paul Bolle <pebolle@...cali.nl>
Cc:	Or Gerlitz <ogerlitz@...lanox.com>,
	Rony Efraim <ronye@...lanox.com>,
	Hadar Hen Zion <hadarh@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] net/mlx4_core: clean up cq_res_start_move_to()

ACK.  OK.

-Jack

On Tue, 14 Jan 2014 20:45:36 +0100
Paul Bolle <pebolle@...cali.nl> wrote:

> Building resource_tracker.o triggers a GCC warning:
>     drivers/net/ethernet/mellanox/mlx4/resource_tracker.c: In
> function 'mlx4_HW2SW_CQ_wrapper':
> drivers/net/ethernet/mellanox/mlx4/resource_tracker.c:3019:16:
> warning: 'cq' may be used uninitialized in this function
> [-Wmaybe-uninitialized] atomic_dec(&cq->mtt->ref_count); ^
> 
> This is a false positive. But a cleanup of cq_res_start_move_to() can
> help GCC here. The code currently uses a switch statement where an
> if/else construct would do too, since only two of the switch's four
> cases can ever occur. Dropping that switch makes the warning go away.
> 
> While we're at it, add some missing braces.
> 
> Signed-off-by: Paul Bolle <pebolle@...cali.nl>
> ---
> v2: adjust to Jack's review.
> 
>  .../net/ethernet/mellanox/mlx4/resource_tracker.c  | 52
> ++++++++-------------- 1 file changed, 19 insertions(+), 33
> deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c
> b/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c index
> 2f3f2bc..15cd659 100644 ---
> a/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c +++
> b/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c @@ -1340,43
> +1340,29 @@ static int cq_res_start_move_to(struct mlx4_dev *dev, int
> slave, int cqn, spin_lock_irq(mlx4_tlock(dev));
>  	r = res_tracker_lookup(&tracker->res_tree[RES_CQ], cqn);
> -	if (!r)
> +	if (!r) {
>  		err = -ENOENT;
> -	else if (r->com.owner != slave)
> +	} else if (r->com.owner != slave) {
>  		err = -EPERM;
> -	else {
> -		switch (state) {
> -		case RES_CQ_BUSY:
> -			err = -EBUSY;
> -			break;
> -
> -		case RES_CQ_ALLOCATED:
> -			if (r->com.state != RES_CQ_HW)
> -				err = -EINVAL;
> -			else if (atomic_read(&r->ref_count))
> -				err = -EBUSY;
> -			else
> -				err = 0;
> -			break;
> -
> -		case RES_CQ_HW:
> -			if (r->com.state != RES_CQ_ALLOCATED)
> -				err = -EINVAL;
> -			else
> -				err = 0;
> -			break;
> -
> -		default:
> +	} else if (state == RES_CQ_ALLOCATED) {
> +		if (r->com.state != RES_CQ_HW)
>  			err = -EINVAL;
> -		}
> +		else if (atomic_read(&r->ref_count))
> +			err = -EBUSY;
> +		else
> +			err = 0;
> +	} else if (state != RES_CQ_HW || r->com.state !=
> RES_CQ_ALLOCATED) {
> +		err = -EINVAL;
> +	} else {
> +		err = 0;
> +	}
>  
> -		if (!err) {
> -			r->com.from_state = r->com.state;
> -			r->com.to_state = state;
> -			r->com.state = RES_CQ_BUSY;
> -			if (cq)
> -				*cq = r;
> -		}
> +	if (!err) {
> +		r->com.from_state = r->com.state;
> +		r->com.to_state = state;
> +		r->com.state = RES_CQ_BUSY;
> +		if (cq)
> +			*cq = r;
>  	}
>  
>  	spin_unlock_irq(mlx4_tlock(dev));

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