netdev - Re: [PATCH net-next] net: add rcu locking when changing early demux

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Message-Id: <20170424.140838.1224449140831206697.davem@davemloft.net>
Date:   Mon, 24 Apr 2017 14:08:38 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     dsa@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, subashab@...eaurora.org
Subject: Re: [PATCH net-next] net: add rcu locking when changing early demux

From: David Ahern <dsa@...ulusnetworks.com>
Date: Sat, 22 Apr 2017 09:33:16 -0700

> systemd-sysctl is triggering a suspicious RCU usage message when
> net.ipv4.tcp_early_demux or net.ipv4.udp_early_demux is changed via
> a sysctl config file:
> 
> [   33.896184] ===============================
> [   33.899558] [ ERR: suspicious RCU usage.  ]
> [   33.900624] 4.11.0-rc7+ #104 Not tainted
> [   33.901698] -------------------------------
> [   33.903059] /home/dsa/kernel-2.git/net/ipv4/sysctl_net_ipv4.c:305 suspicious rcu_dereference_check() usage!
> [   33.905724]
> other info that might help us debug this:
> 
> [   33.907656]
> rcu_scheduler_active = 2, debug_locks = 0
> [   33.909288] 1 lock held by systemd-sysctl/143:
> [   33.910373]  #0:  (sb_writers#5){.+.+.+}, at: [<ffffffff8123a370>] file_start_write+0x45/0x48
> [   33.912407]
> stack backtrace:
> [   33.914018] CPU: 0 PID: 143 Comm: systemd-sysctl Not tainted 4.11.0-rc7+ #104
> [   33.915631] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [   33.917870] Call Trace:
> [   33.918431]  dump_stack+0x81/0xb6
> [   33.919241]  lockdep_rcu_suspicious+0x10f/0x118
> [   33.920263]  proc_configure_early_demux+0x65/0x10a
> [   33.921391]  proc_udp_early_demux+0x3a/0x41
> 
> add rcu locking to proc_configure_early_demux.
> 
> Fixes: dddb64bcb3461 ("net: Add sysctl to toggle early demux for tcp and udp")
> Signed-off-by: David Ahern <dsa@...ulusnetworks.com>

Applied, thanks David.