Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 30 Mar 2023 23:50:09 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc:     netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
        Steve Glendinning <steve.glendinning@shawell.net>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net v4] smsc911x: only update stats when interface is up
Message-ID: <20230330235009.4b6d4b8e@kernel.org>
In-Reply-To: <ZCZ+tFtp9NBBjiqv@ninjato>
References: <20230329064010.24657-1-wsa+renesas@sang-engineering.com>
        <20230329123958.045c9861@kernel.org>
        <ZCSWJxuu1EY/zBFm@shikoro>
        <20230329131724.4484a881@kernel.org>
        <ZCZ+tFtp9NBBjiqv@ninjato>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Fri, 31 Mar 2023 08:33:24 +0200 Wolfram Sang wrote:
> > Okay, core changes aside - does pm_runtime_put() imply an RCU sync?
> > Otherwise your check in get_stats is racy...  
> 
> From some light research, I can't find a trace of RCU sync. Pity, I'll
> need to move furhter investigation to later. I'll report back if I have
> something, but it may take a while. Thanks for the help!

If you don't want to spend too much time you can just call it yourself
right? :) Put a synchronize_rcu() with a comment about concurrent stat
reading after pdata->is_open = false; and that's it?