netdev - Re: [PATCH net] net: systemport: Fix 64-bit stats deadlock

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Message-Id: <20170915.142511.221689318302073484.davem@davemloft.net>
Date:   Fri, 15 Sep 2017 14:25:11 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     f.fainelli@...il.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, jqiaoulk@...il.com
Subject: Re: [PATCH net] net: systemport: Fix 64-bit stats deadlock

From: Florian Fainelli <f.fainelli@...il.com>
Date: Tue, 12 Sep 2017 13:14:26 -0700

> We can enter a deadlock situation because there is no sufficient protection
> when ndo_get_stats64() runs in process context to guard against RX or TX NAPI
> contexts running in softirq, this can lead to the following lockdep splat and
> actual deadlock was experienced as well with an iperf session in the background
> and a while loop doing ifconfig + ethtool.
 ...
> So just remove the u64_stats_update_begin()/end() pair in ndo_get_stats64()
> since it does not appear to be useful for anything. No inconsistency was
> observed with either ifconfig or ethtool, global TX counts equal the sum of
> per-queue TX counts on a 32-bit architecture.
> 
> Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

Applied.