linux-kernel - Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.00.1012101533400.13986@router.home>
Date:	Fri, 10 Dec 2010 15:45:15 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Mikael Pettersson <mikpe@...uu.se>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	John Stultz <johnstul@...ibm.com>
Subject: Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM

On Fri, 10 Dec 2010, Eric Dumazet wrote:

> > There is certainly a major difference in that execution of a stream of
> > instructions on the same cpu is guaranteed to have a coherent view of
> > the data. That is not affected by interrupts etc.
> >
>
> We dont care of interrupts. We care of doing a transaction over a
> complex set of data, that cannot be done using an atomic op (or we need
> a spinlock/mutex/rwlock), and should not because of performance.

So what? The cpu gives you incoherent view of data somewhere when only
processing data from a single cpu?

If you have remote data accesses (loop summing the data?) and you have to
be concerned about data coherence then you CANNOT use this_cpu_ops since
they are not guaranteed to be coherent to other processors.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/