netdev - Re: [PATCH net] net: Fix inconsistent rtnl_lock usage on dev_get

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Message-Id: <20170107.210324.2205499330408276919.davem@davemloft.net>
Date:   Sat, 07 Jan 2017 21:03:24 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     michael.chan@...adcom.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] net: Fix inconsistent rtnl_lock usage on
 dev_get_stats().

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 06 Jan 2017 12:13:23 -0800

> Well, there are cases where RTNL is quite contended, but supervisions
> like to get /proc/net/devices or various sysfs attributes
> (netstat_show() can be called very very often
> for /sys/class/net/*/statistics/*) in a reasonable amount of time.
> 
> I fear that such a change will add drifts, when devices are constantly
> added/removed.

It stands to reason that RTNETLINK could use pure RCU locking for
device and stat dumps, and frankly that would make their usage and
overhead superior to poking files over and over.