Re: Hypervisor crash(!) on xl cpupool-numa-split

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

On 01/28/11 12:07, Andre Przywara wrote:
> Juergen Gross wrote:
>> On 01/28/11 00:18, Andre Przywara wrote:
>>> Hi,
>>>
>>> when I boot my machine without restricting Dom0 (dom0_mem=
>>> dom0_max_vcpus=) I get an _hypervisor_ crash when I run
>>> # xl cpupool-numa-split
>>> If Dom0's resources are limited on the Xen cmdline, everything works
>>> fine.
>>> The crashdump points to a scheduling problem with weights, so I assume
>>> the NUMA distribution algorithm some fools the hypervisor completely.
>>>
>>> I will investigate this further tomorrow, but maybe someone has some
>>> good idea.
>>
>> I've seen this once with an older cpupool version on a 24 processor
>> machine.
>> It was NOT related to NUMA, but did occur only on reboot after a Dom0
>> panic.
>> The machine had an init script creating a cpupool and populating it with
>> cpus. The machine was in a panic loop due to the BUG in sched_acct
>> then until
>> it was resetted manually. After the reset the problem was gone.
>>
>> As I was never able to reproduce the problem later (the same software is
>> running on dozens of machines!), I assumed there was a problem related to
>> the first Dom0 panic, may be some destroyed BIOS tables.
>>
>> Can the crash be reproduced easily?
> Yes.
> If I don't specify dom0_max_vcpus= and dom0_mem= on the Xen cmdline, I
> can reliably trigger the crash with xl cpupool-numa-split.
> Omitting dom0_max_vcpus only does not suffice.

Do I understand correctly?
No crash with only dom0_max_vcpus= and no crash with only dom0_mem= ?

Could you try this patch?

diff -r b59f04eb8978 xen/common/schedule.c
--- a/xen/common/schedule.c     Fri Jan 21 18:06:23 2011 +0000
+++ b/xen/common/schedule.c     Fri Jan 28 12:42:46 2011 +0100
@@ -1301,7 +1301,9 @@ void schedule_cpu_switch(unsigned int cp

      idle = idle_vcpu[cpu];
      ppriv = SCHED_OP(new_ops, alloc_pdata, cpu);
+    BUG_ON(ppriv == NULL);
      vpriv = SCHED_OP(new_ops, alloc_vdata, idle, idle->domain->sched_priv);
+    BUG_ON(vpriv == NULL);

      pcpu_schedule_lock_irqsave(cpu, flags);



-- 
Juergen Gross                 Principal Developer Operating Systems
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