Re: [PATCH net-next 2/4] net: dev: Remove get_cpu() in netif_rx_internal().

From: Eric Dumazet <edumazet@google.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: bpf <bpf@vger.kernel.org>, netdev <netdev@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH net-next 2/4] net: dev: Remove get_cpu() in netif_rx_internal().
Date: Wed, 2 Feb 2022 09:14:22 -0800	[thread overview]
Message-ID: <CANn89iJoLSRP0zckRN0HtY=ii7VDkcoCP0SzMdzL99Tiw=EJDw@mail.gmail.com> (raw)
In-Reply-To: <20220202122848.647635-3-bigeasy@linutronix.de>

On Wed, Feb 2, 2022 at 4:28 AM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> The get_cpu() usage was added in commit
>     b0e28f1effd1d ("net: netif_rx() must disable preemption")
>
> because ip_dev_loopback_xmit() invoked netif_rx() with enabled preemtion
> causing a warning in smp_processor_id(). The function netif_rx() should
> only be invoked from an interrupt context which implies disabled
> preemption. The commit
>    e30b38c298b55 ("ip: Fix ip_dev_loopback_xmit()")
>
> was addressing this and replaced netif_rx() with in netif_rx_ni() in
> ip_dev_loopback_xmit().
>
> Based on the discussion on the list, the former patch (b0e28f1effd1d)
> should not have been applied only the latter (e30b38c298b55).
>
> Remove get_cpu() since the function is supossed to be invoked from
> context with stable per-CPU pointers (either by disabling preemption or
> software interrupts).
>
> Link: https://lkml.kernel.org/r/20100415.013347.98375530.davem@davemloft.net
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks !