linux-kernel - Re: [PATCH net-next 8/8] net: mscc: ocelot: fix ineffective WARN_ON() in ocelot

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Message-ID: <529b10f7-6f74-9fdb-db45-0ba589ba0cb3@intel.com>
Date:   Wed, 12 Apr 2023 14:23:06 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Vladimir Oltean <vladimir.oltean@....com>, <netdev@...r.kernel.org>
CC:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Claudiu Manoil" <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        <UNGLinuxDriver@...rochip.com>,
        Colin Foster <colin.foster@...advantage.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 8/8] net: mscc: ocelot: fix ineffective WARN_ON()
 in ocelot_stats.c



On 4/12/2023 5:47 AM, Vladimir Oltean wrote:
> Since it is hopefully now clear that, since "last" and "layout[i].reg"
> are enum types and not addresses, the existing WARN_ON() is ineffective
> in checking that the _addresses_ are sorted in the proper order.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---

This is definitely more clear after reviewing the other code dealing
with these encoded register addresses.

Nice fix.

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

Thanks,
Jake

>  drivers/net/ethernet/mscc/ocelot_stats.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mscc/ocelot_stats.c b/drivers/net/ethernet/mscc/ocelot_stats.c
> index e82c9d9d0ad3..5c55197c7327 100644
> --- a/drivers/net/ethernet/mscc/ocelot_stats.c
> +++ b/drivers/net/ethernet/mscc/ocelot_stats.c
> @@ -901,6 +901,17 @@ static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
>  		if (!layout[i].reg)
>  			continue;
>  
> +		/* enum ocelot_stat must be kept sorted in the same order
> +		 * as the addresses behind layout[i].reg in order to have
> +		 * efficient bulking
> +		 */
> +		if (last) {
> +			WARN(ocelot->map[SYS][last & REG_MASK] >= ocelot->map[SYS][layout[i].reg & REG_MASK],
> +			     "reg 0x%x had address 0x%x but reg 0x%x has address 0x%x, bulking broken!",
> +			     last, ocelot->map[SYS][last & REG_MASK],
> +			     layout[i].reg, ocelot->map[SYS][layout[i].reg & REG_MASK]);
> +		}
> +
>  		if (region && ocelot->map[SYS][layout[i].reg & REG_MASK] ==
>  		    ocelot->map[SYS][last & REG_MASK] + 4) {
>  			region->count++;
> @@ -910,12 +921,6 @@ static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
>  			if (!region)
>  				return -ENOMEM;
>  
> -			/* enum ocelot_stat must be kept sorted in the same
> -			 * order as layout[i].reg in order to have efficient
> -			 * bulking
> -			 */
> -			WARN_ON(last >= layout[i].reg);
> -
>  			region->base = layout[i].reg;
>  			region->first_stat = i;
>  			region->count = 1;