From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [Bug #13116] Can't boot with nosmp
Date: Sun, 3 May 2009 16:21:37 -0700
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To: David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>, Linux Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kernel Testers List <kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Stephen Hemminger <shemminger-ZtmgI6mnKB3QT0dZR+AlfA@public.gmane.org>

On Tue, Apr 28, 2009 at 3:14 PM, David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> w=
rote:
> On Sun, 26 Apr 2009, Dan Williams wrote:
>
>> Rafael J. Wysocki wrote:
>> > This message has been generated automatically as a part of a repor=
t
>> > of recent regressions.
>> >
>> > The following bug entry is on the current list of known regression=
s
>> > from 2.6.29. =A0Please verify if it still should be listed and let=
 me know
>> > (either way).
>>
>> This is still unresolved.
>>
>> Stephen, please send your config.
>>
>
> Given the stack for the initial report, why would a config other than
> enabling CONFIG_DMA_ENGINE help if there's no ifdefs involved?

=2E..because I have been unable to reproduce it and wanted to start
eliminating differences in our respective setups.  I have booted an
oversubscribed (8-virtual / 2 physical cpus) kvm instance with 2.6.29
and have not seen this reproduce.

> This is happening in the for_each_possible_cpu() loop within
> dma_channel_rebalance(), which makes sense since the machine boots fi=
ne
> normally but not with `nosmp'.
>
> channel_table[] is not being initialized per-cpu for non-online cpus?

I'm grasping, but could this possibly be a kvm quirk whereby
cpu_possible_map gets out of sync with cpu_online_map in the 'nosmp'
case?

--
Dan