From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arun Sharma <asharma@fb.com>
Subject: Re: Kernel crash after using new Intel NIC (igb)
Date: Tue, 24 May 2011 23:06:09 -0700
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Cc: Arun Sharma <asharma@fb.com>,
	Maximilian Engelhardt <maxi@daemonizer.de>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	StuStaNet Vorstand <vorstand@stusta.mhn.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
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On Wed, May 25, 2011 at 04:44:29AM +0200, Eric Dumazet wrote:
> 
> Hmm, thanks for the report. Are you running x86 or another arch ?
> 

This was on x86.

> We probably need some sort of memory barrier.
> 
> However, locking this central lock makes the thing too slow, I'll try to
> use an atomic_inc_return on p->refcnt instead. (and then lock
> unused_peers.lock if we got a 0->1 transition)

Another possibility is to do the list_empty() check twice. Once without
taking the lock and again with the spinlock held.

 -Arun