Re: xen-4.1: PV domain hanging at startup, jiffies stopped

[Marek Marczykowski <marmarek@mimuw.edu.pl>]

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On 29.08.2011 22:07, Konrad Rzeszutek Wilk wrote:
> On Sun, Aug 28, 2011 at 03:13:46PM +0200, Marek Marczykowski wrote:
>> Hey,
>>
>> I'm experiencing strange problem: non-deterministic PV domain hang, only
>> on some machines (with fast SSD drive). I've tried xen-4.1.0 and
>> xen-4.1.1 with many kernels different kernels:
>> VM:
>>  - 2.6.38.3 xenlinux based on SUSE package
>>  - vanilla 3.0.3
>>  - vanilla 3.1 rc2
>> dom0:
>>  - 2.6.38.3 xenlinux based on SUSE package
>>  - vanilla 3.1 rc2
>>
>> Result always the same: sometimes VM hang at startup, SysRq-T shows
>> modprobe waiting in "wait_for_devices" (concretely schedule_timeout) and
>> jiffies counter not increasing between task-states dumps.
>>
>> The only found thing (probably) connected with this problem are domU
>> kernel messages:
>> CE: xen increased min_delta_ns to 150000 nsec
>> (...)
>> CE: xen increased min_delta_ns to 4000000 nsec
>> CE: Reprogramming failure. Giving up
>>
>> This messages doesn't exists in successful boot.
>>
>> I've also tried some options to xen and domU kernel, but without success
>> (all combinations):
> 
> BTW, your 'xencons=..' and 'swiotlb=force' are obsolete. Use
> 'console=hvc0' and 'iommu=soft'. The 'swiotlb=force' kills performance.
> 
>> xen: tsc=unstable, cpufreq=none
>> domU: nohz=off, clocksource=tsc
>>
>> Some combination of above options lowered frequency of problem (ex
>> tsc=unstable + nohz=off), but it happens quite often - like 1 of 15
>> boots fails.
>>
>> Have you idea what is the cause and what can help?
> 
> The problem looks to be xenwatch stuck. So the problem is in Dom0 right?

This "R" state of xenwatch looks like result of SysRq, which dumps data...

[  118.679707]  [<ffffffff812a8081>] handle_sysrq+0x21/0x30
[  118.679707]  [<ffffffff8128db49>] sysrq_handler+0xb9/0xe0
[  118.679707]  [<ffffffff8128ff50>] xenwatch_thread+0xb0/0x170

And the problem is at DomU boot, Dom0 works without any problems.

-- 
Pozdrawiam / Best Regards,
Marek Marczykowski         | RLU #390519
marmarek at mimuw edu pl   | xmpp:marmarek at staszic waw pl


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