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:   Mon, 22 Aug 2022 11:05:43 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>, netdev@vger.kernel.org
Subject: Re: [PATCH 9/9] u64_stat: Remove the obsolete fetch_irq() variants
Message-ID: <20220822110543.4f1a8962@kernel.org>
In-Reply-To: <YwOd7Ex7W21WzQ8N@linutronix.de>
References: <20220817162703.728679-1-bigeasy@linutronix.de>
        <20220817162703.728679-10-bigeasy@linutronix.de>
        <20220817112745.4efd8217@kernel.org>
        <Yv5aSquR9S2KxUr2@linutronix.de>
        <20220818090200.4c6889f2@kernel.org>
        <Yv5v1E6mfpcxjnLV@linutronix.de>
        <20220818104505.010ff950@kernel.org>
        <YwOd7Ex7W21WzQ8N@linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Mon, 22 Aug 2022 17:17:00 +0200 Sebastian Andrzej Siewior wrote:
> Using u64_stats_fetch_begin() is most likely wrong in networking because
> the stats are updated while packets are received which is either in IRQ
> or in BH (except maybe for the SPI/I2C ethernet driver). The _bh()
> version was replaced with _irq() for netpoll reasons.
> u64_stats_fetch_begin() does not disable any of those two (IRQ, BH) on
> 32bit-UP and does not use a seqcount so it is possible that an update
> happens during the read out of stats. Let me look=E2=80=A6
> 	drivers/net/ethernet/cortina/gemini.c
> reads in net_device_ops::ndo_get_stats64(), updates in NAPI.
>=20
> 	drivers/net/ethernet/huawei/hinic/hinic_rx.c
> reads in net_device_ops::ndo_get_stats64() and
> ethtool_ops::get_ethtool_stats(), updates in NAPI. Good.
>=20
> So I guess these want be fixed properly instead of silently via the
> series?

Guess so, but it shouldn't be extra work if we're delaying the driver
conversion till 6.1?