linux-kernel - Re: specjbb2005 and aim7 regression with 2.6.32-rc kernels

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 PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

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

Date:	Mon, 09 Nov 2009 10:55:01 +0100
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: specjbb2005 and aim7 regression with 2.6.32-rc kernels

On Mon, 2009-11-09 at 10:15 +0100, Peter Zijlstra wrote:
> On Mon, 2009-11-09 at 08:09 +0100, Mike Galbraith wrote:
> > +       smp_read_barrier_depends();
> >         cpumask_setall(cpus);
> > +       cpumask_and(cpus, cpus, cpu_online_mask);
> 
> 
> how about: cpumask_copy(cpus, cpu_online_mask); ?

Yeah, better.

> Also, iirc cpu_online_mask is guaranteed stable when preemption is
> disabled, otherwise you need to use get/put_online_cpus(), an
> rmb_depends() won't do.

Ok..  I do need a barrier though.  I don't see how it can be stable when
three other CPUs diddle it.  It looks to me like it's stable only when
all diddlers serialize on the runqueue lock.  (which iff correct means
31 has bugs too, so I'm very likely dead wrong) 

/me has very little experience with smp memory woes.  Tripping over one
is one thing, fixing the bugger is an entirely different matter.

(what I'm about to compile would probably get me spanked on lkml;)

	-Mike

--
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/