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

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Message-ID: <20140116094738.025833a6@jpm-OptiPlex-GX620>
Date:	Thu, 16 Jan 2014 09:47:38 +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 2/2] net/mlx4_core: clean up srq_res_start_move_to()

ACK.  OK.

-Jack

On Tue, 14 Jan 2014 20:46:52 +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_SRQ_wrapper':
> drivers/net/ethernet/mellanox/mlx4/resource_tracker.c:3202:17:
> warning: 'srq' may be used uninitialized in this function
> [-Wmaybe-uninitialized] atomic_dec(&srq->mtt->ref_count); ^
> 
> This is a false positive. But a cleanup of srq_res_start_move_to() can
> help GCC here. The code currently uses a switch statement where a
> plain if/else would do, 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, and convert state to the
> correct type.
> 
> Signed-off-by: Paul Bolle <pebolle@...cali.nl>
> ---
> v2: adjust to Jack's review.
> 
>  .../net/ethernet/mellanox/mlx4/resource_tracker.c  | 46
> ++++++++-------------- 1 file changed, 16 insertions(+), 30
> deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c
> b/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c index
> 15cd659..4acd84c 100644 ---
> a/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c +++
> b/drivers/net/ethernet/mellanox/mlx4/resource_tracker.c @@ -1371,7
> +1371,7 @@ static int cq_res_start_move_to(struct mlx4_dev *dev, int
> slave, int cqn, } 
>  static int srq_res_start_move_to(struct mlx4_dev *dev, int slave,
> int index,
> -				 enum res_cq_states state, struct
> res_srq **srq)
> +				 enum res_srq_states state, struct
> res_srq **srq) {
>  	struct mlx4_priv *priv = mlx4_priv(dev);
>  	struct mlx4_resource_tracker *tracker =
> &priv->mfunc.master.res_tracker; @@ -1380,39 +1380,25 @@ static int
> srq_res_start_move_to(struct mlx4_dev *dev, int slave, int index, 
>  	spin_lock_irq(mlx4_tlock(dev));
>  	r = res_tracker_lookup(&tracker->res_tree[RES_SRQ], index);
> -	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_SRQ_BUSY:
> -			err = -EINVAL;
> -			break;
> -
> -		case RES_SRQ_ALLOCATED:
> -			if (r->com.state != RES_SRQ_HW)
> -				err = -EINVAL;
> -			else if (atomic_read(&r->ref_count))
> -				err = -EBUSY;
> -			break;
> -
> -		case RES_SRQ_HW:
> -			if (r->com.state != RES_SRQ_ALLOCATED)
> -				err = -EINVAL;
> -			break;
> -
> -		default:
> +	} else if (state == RES_SRQ_ALLOCATED) {
> +		if (r->com.state != RES_SRQ_HW)
>  			err = -EINVAL;
> -		}
> +		else if (atomic_read(&r->ref_count))
> +			err = -EBUSY;
> +	} else if (state != RES_SRQ_HW || r->com.state !=
> RES_SRQ_ALLOCATED) {
> +		err = -EINVAL;
> +	}
>  
> -		if (!err) {
> -			r->com.from_state = r->com.state;
> -			r->com.to_state = state;
> -			r->com.state = RES_SRQ_BUSY;
> -			if (srq)
> -				*srq = r;
> -		}
> +	if (!err) {
> +		r->com.from_state = r->com.state;
> +		r->com.to_state = state;
> +		r->com.state = RES_SRQ_BUSY;
> +		if (srq)
> +			*srq = r;
>  	}
>  
>  	spin_unlock_irq(mlx4_tlock(dev));

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