linux-kernel - Re: [PATCH net] net: mvpp2: Don't re-use loop iterator

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Message-ID: <20240725080440.41c2fd97@kernel.org>
Date: Thu, 25 Jul 2024 08:04:40 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Stefan Chulski <stefanc@...vell.com>, Marcin Wojtas
 <marcin.s.wojtas@...il.com>, Russell King <linux@...linux.org.uk>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] net: mvpp2: Don't re-use loop iterator

On Wed, 24 Jul 2024 11:06:56 -0500 Dan Carpenter wrote:
> This function has a nested loop.  The problem is that both the inside
> and outside loop use the same variable as an iterator.  I found this
> via static analysis so I'm not sure the impact.  It could be that it
> loops forever or, more likely, the loop exits early.

> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 8c45ad983abc..0d62a33afa80 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -953,13 +953,13 @@ static void mvpp2_bm_pool_update_fc(struct mvpp2_port *port,
>  static void mvpp2_bm_pool_update_priv_fc(struct mvpp2 *priv, bool en)
>  {
>  	struct mvpp2_port *port;
> -	int i;
> +	int i, j;
>  
>  	for (i = 0; i < priv->port_count; i++) {
>  		port = priv->port_list[i];
>  		if (port->priv->percpu_pools) {
> -			for (i = 0; i < port->nrxqs; i++)
> -				mvpp2_bm_pool_update_fc(port, &port->priv->bm_pools[i],
> +			for (j = 0; j < port->nrxqs; j++)
> +				mvpp2_bm_pool_update_fc(port, &port->priv->bm_pools[j],
>  							port->tx_fc & en);
>  		} else {
>  			mvpp2_bm_pool_update_fc(port, port->pool_long, port->tx_fc & en);

Stefan, can you comment? priv->bm_pools are global (not per port)
AFAICT, so this may be semi-intentional.