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Date: Mon, 1 Dec 2014 12:36:34 -0800
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Subject: Re: frequent lockups in 3.18rc4
From: Linus Torvalds <torvalds@linux-foundation.org>
To: =?UTF-8?Q?D=C3=A2niel_Fraga?= <fragabr@gmail.com>,
        Dave Jones <davej@redhat.com>, Sasha Levin <sasha.levin@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, Dec 1, 2014 at 12:28 PM, Dâniel Fraga <fragabr@gmail.com> wrote:
>
>         Hi Paul. Please, I'd like the patch, because without
> preemption, I'm unable to trigger this bug.

Ok, that's already interesting information. And yes, it would probably
be interesting to see if CONFIG_PREEMPT=y but !CONFIG_TREE_PREEMPT_RCU
then solves it too, to narrow it down to one but not the other..

DaveJ - what about your situation? The standard Fedora kernels use
CONFIG_PREEMPT_VOLUNTARY, do you have CONFIG_PREEMPT and
CONFIG_TREE_PREEMPT_RCU enabled? I think you and Sasha both saw some
RCU oddities too, no?

                    Linus