From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Vegard Nossum <vegardno@ifi.uio.no>,
Pekka Enberg <penberg@cs.helsinki.fi>,
casteyde.christian@free.fr,
Andrew Morton <akpm@linux-foundation.org>,
netdev@vger.kernel.org, bugzilla-daemon@bugzilla.kernel.org,
bugme-daemon@bugzilla.kernel.org
Subject: Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc_skb
Date: Tue, 10 May 2011 22:45:53 +0200 [thread overview]
Message-ID: <1305060353.2437.26.camel@edumazet-laptop> (raw)
In-Reply-To: <alpine.DEB.2.00.1105101531160.4023@router.home>
Le mardi 10 mai 2011 à 15:33 -0500, Christoph Lameter a écrit :
> On Tue, 10 May 2011, Eric Dumazet wrote:
>
> > Le mardi 10 mai 2011 à 14:38 -0500, Christoph Lameter a écrit :
> >
> > > Optimizing? You think about this as concurrency issue between multiple
> > > cpus. That is fundamentally wrong. This is dealing with access to per cpu
> > > data and the concurrency issues are only with code running on the *same*
> > > cpu.
> > >
> >
> > If you enable irqs, then this object can be allocated by _this_ cpu and
> > given to another one.
>
> That will cause an incrementing of the tid.
>
> > Another cpu can free the page, forcing you to call a very expensive
> > function, that might give obsolete result as soon it returns.
>
> No the other cpu cannot free the page since the page is pinned by
> the current cpu (see PageFrozen()).
>
What happens then ? Other cpu calls kfree() on last nonfreed object for
this slab, and yet the page stay frozen ? How this page is going to be
freed at all ?
> > Maybe I am just tired tonight, this seems very obvious, I must miss
> > something.
>
> Yeah you are way off thinking about cpu to cpu concurrency issues that do
> not apply here.
I fail to understand how current cpu can assert page ownership, if IRQs
are enabled, this seems obvious it cannot.
next prev parent reply other threads:[~2011-05-10 20:45 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-33502-10286@https.bugzilla.kernel.org/>
2011-04-18 22:38 ` [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc_skb Andrew Morton
2011-04-19 2:51 ` Eric Dumazet
2011-04-19 3:09 ` Eric Dumazet
2011-04-19 3:20 ` Eric Dumazet
2011-04-19 17:10 ` Christoph Lameter
2011-04-19 20:17 ` Eric Dumazet
2011-04-19 21:18 ` Christoph Lameter
2011-04-20 5:04 ` Eric Dumazet
2011-04-20 14:04 ` Christoph Lameter
2011-04-20 5:56 ` Pekka Enberg
2011-04-20 6:04 ` Eric Dumazet
2011-04-20 7:45 ` casteyde.christian
2011-04-20 7:49 ` Pekka Enberg
2011-04-20 8:09 ` Eric Dumazet
2011-04-20 8:21 ` Pekka Enberg
2011-04-20 9:07 ` Eric Dumazet
2011-04-20 10:02 ` Eric Dumazet
2011-04-20 14:05 ` Christoph Lameter
2011-04-20 14:26 ` Eric Dumazet
2011-04-20 14:42 ` Christoph Lameter
2011-04-20 15:01 ` Eric Dumazet
2011-04-20 15:15 ` Vegard Nossum
2011-04-20 15:34 ` Eric Dumazet
2011-04-20 15:17 ` Christoph Lameter
2011-04-20 15:30 ` Eric Dumazet
2011-04-20 19:36 ` Christian Casteyde
2011-04-20 19:55 ` Eric Dumazet
2011-04-20 20:32 ` Eric Dumazet
2011-05-05 6:18 ` Eric Dumazet
2011-05-05 6:22 ` Pekka Enberg
2011-05-05 6:50 ` Eric Dumazet
2011-05-05 18:40 ` Christoph Lameter
2011-05-05 18:48 ` Eric Dumazet
2011-05-05 19:05 ` Christoph Lameter
2011-05-09 19:44 ` Pekka Enberg
2011-05-09 20:04 ` Christoph Lameter
2011-05-09 20:06 ` Pekka Enberg
2011-05-10 8:43 ` Eric Dumazet
2011-05-10 9:47 ` Pekka Enberg
2011-05-10 10:03 ` Eric Dumazet
2011-05-10 10:10 ` Pekka Enberg
2011-05-10 10:03 ` Pekka Enberg
2011-05-10 10:17 ` Eric Dumazet
2011-05-10 10:19 ` Pekka Enberg
2011-05-10 11:52 ` Eric Dumazet
2011-05-10 12:24 ` Vegard Nossum
2011-05-10 16:39 ` Christoph Lameter
2011-05-10 17:14 ` Eric Dumazet
2011-05-10 17:30 ` Christoph Lameter
2011-05-10 17:43 ` Christoph Lameter
2011-05-10 18:05 ` Eric Dumazet
2011-05-10 18:28 ` Christoph Lameter
2011-05-10 19:05 ` Christoph Lameter
2011-05-10 19:32 ` Eric Dumazet
2011-05-10 19:38 ` Christoph Lameter
2011-05-10 20:06 ` Eric Dumazet
2011-05-10 20:33 ` Christoph Lameter
2011-05-10 20:45 ` Eric Dumazet [this message]
2011-05-10 21:22 ` Christoph Lameter
2011-05-11 3:12 ` Eric Dumazet
2011-05-12 14:36 ` Christoph Lameter
2011-05-13 21:15 ` [PATCH] slub: Make CONFIG_PAGE_ALLOC work with new fastpath Christoph Lameter
2011-05-13 21:26 ` Eric Dumazet
2011-05-10 18:07 ` [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc_skb Christoph Lameter
2011-05-10 16:33 ` Christoph Lameter
2011-04-19 17:09 ` Christoph Lameter
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