Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 10 Feb 2021 12:45:49 +0200
From:   Vladimir Oltean <olteanv@gmail.com>
To:     Nikolay Aleksandrov <nikolay@nvidia.com>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        bridge@lists.linux-foundation.org, Roopa Prabhu <roopa@nvidia.com>,
        Jiri Pirko <jiri@resnulli.us>,
        Ido Schimmel <idosch@idosch.org>,
        Claudiu Manoil <claudiu.manoil@nxp.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        UNGLinuxDriver@microchip.com, Vadym Kochan <vkochan@marvell.com>,
        Taras Chornyi <tchornyi@marvell.com>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        Ioana Ciornei <ioana.ciornei@nxp.com>,
        Ivan Vecera <ivecera@redhat.com>, linux-omap@vger.kernel.org
Subject: Re: [PATCH v3 net-next 00/11] Cleanup in brport flags switchdev
 offload for DSA
Message-ID: <20210210104549.ga3lgjafn5x3htwj@skbuf>
References: <20210210091445.741269-1-olteanv@gmail.com>
 <a8e9284b-f0a6-0343-175d-8c323371ef8d@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <a8e9284b-f0a6-0343-175d-8c323371ef8d@nvidia.com>
Precedence: bulk

Hi Nikolay,

On Wed, Feb 10, 2021 at 12:31:43PM +0200, Nikolay Aleksandrov wrote:
> Hi Vladimir,
> Let's take a step back for a moment and discuss the bridge unlock/lock sequences
> that come with this set. I'd really like to avoid those as they're a recipe
> for future problems. The only good way to achieve that currently is to keep
> the PRE_FLAGS call and do that in unsleepable context but move the FLAGS call
> after the flags have been changed (if they have changed obviously). That would
> make the code read much easier since we'll have all our lock/unlock sequences
> in the same code blocks and won't play games to get sleepable context.
> Please let's think and work in that direction, rather than having:
> +	spin_lock_bh(&p->br->lock);
> +	if (err) {
> +		netdev_err(p->dev, "%s\n", extack._msg);
> +		return err;
>  	}
> +
> 
> which immediately looks like a bug even though after some code checking we can
> verify it's ok. WDYT?
> 
> I plan to get rid of most of the br->lock since it's been abused for a very long
> time because it's essentially STP lock, but people have started using it for other
> things and I plan to fix that when I get more time.

This won't make the sysfs codepath any nicer, will it?