netdev - Re: WARNING: at mm/slub.c:3357, kernel BUG at mm/slub.c:3413

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Message-ID: <1321900743.10470.31.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Mon, 21 Nov 2011 19:39:03 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Andrew Bresticker <abrestic@...gle.com>
Cc:	"Alex,Shi" <alex.shi@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: WARNING: at mm/slub.c:3357, kernel BUG at mm/slub.c:3413

Le lundi 21 novembre 2011 à 18:35 +0100, Markus Trippelsdorf a écrit :

> New one:

...

I was just wondering if you were using CONFIG_CGROUPS=y, and if yes, if
you could try to disable it.

css_get_next() looks very buggy, the read_lock()/read_unlock() protects
nothing at all, RCU rules are not respected.


commit c1e2ee2dc43657 (memcg: replace ss->id_lock with a rwlock) missed
the point of doing a true RCU conversion to get even better results, and
fact that previous code was buggy as well.

[ After rcu lookup, we must get a stable reference, then recheck the
key , or else we can manipulate something that was queued for deletion.]

An example of a correct RCU conversion was done in commit 8af088710d1
(posix-timers: RCU conversion)



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