netdev - Re: [PATCH net-next] tcp: fix lockdep splat in tcp_snd_una

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Message-Id: <20160504.005443.219521798076710212.davem@davemloft.net>
Date:	Wed, 04 May 2016 00:54:43 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	romieu@...zoreil.com, festevam@...il.com, edumazet@...gle.com,
	chuck.lever@...cle.com, trond.myklebust@...marydata.com,
	netdev@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: fix lockdep splat in tcp_snd_una_update()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 03 May 2016 16:56:03 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> tcp_snd_una_update() and tcp_rcv_nxt_update() call
> u64_stats_update_begin() either from process context or BH handler.
> 
> This triggers a lockdep splat on 32bit & SMP builds.
> 
> We could add u64_stats_update_begin_bh() variant but this would
> slow down 32bit builds with useless local_disable_bh() and
> local_enable_bh() pairs, since we own the socket lock at this point.
> 
> I add sock_owned_by_me() helper to have proper lockdep support
> even on 64bit builds, and new u64_stats_update_begin_raw()
> and u64_stats_update_end_raw methods.
> 
> Fixes: c10d9310edf5 ("tcp: do not assume TCP code is non preemptible")
> Reported-by: Fabio Estevam <festevam@...il.com>
> Diagnosed-by: Francois Romieu <romieu@...zoreil.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied.