linux-kernel - Re: [PATCH] sched_groups are expected to be circular linked list, make it so right after allocation

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Message-ID: <1336657544.2527.116.camel@twins>
Date:	Thu, 10 May 2012 15:45:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Igor Mammedov <imammedo@...hat.com>
Cc:	Jiang Liu <liuj97@...il.com>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, pjt@...gle.com, tglx@...utronix.de,
	seto.hidetoshi@...fujitsu.com
Subject: Re: [PATCH] sched_groups are expected to be circular linked list,
 make it so right after allocation

On Thu, 2012-05-10 at 15:26 +0200, Igor Mammedov wrote:
> [  141.699854] sched: Bonkers domain doesn't include its own cpu: 3 0-1,3
> [  141.725038] sched: Bonkers domain doesn't include its own cpu: 3 0-1 

Whee!! so cpu_mask (active_mask) does include 3, but the tl->mask()
doesn't.

> [  141.775040] sched: Topology is hosed for CPU-3!!
> [  141.775596] sched: domain: NODE 0-1
> [  141.776004] sched:  group: 0-1
> 
This seems to suggest its the node topology being wrecked.

which with your code-base would be
cpu_node_mask()->sched_domain_node_span()..

Did you specify any node topology on the qemu command line? If not, it
should all reduce to cpumask_of_node(0).

identify_secondary_cpu()->identify_cpu()->numa_add_cpu() should set that
bit. which is well before the CPU_ONLINE->cpuset_update_active_cpus()
sched domain rebuild.


Most puzzling. Can you dig a little deeper as to why these masks might
be wrong? Also, can you reproduce on actual hardware? The reason I never
use kvm or other virt for debugging is that I always end up spending
time chasing virt bugs, and I hate virt..
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