Re: [uml-devel] [PATCH v3] um: Switch clocksource to hrtimers

[Richard Weinberger <richard@nod.at>]

Am 02.11.2015 um 09:41 schrieb Anton Ivanov:
> On 02/11/15 08:37, Richard Weinberger wrote:
>> Hi!
>>
>> Am 02.11.2015 um 09:14 schrieb Anton Ivanov:
>>> I was testing under similar conditions (CPU pinning using taskset -c 0 on a multicore).
>>>
>>> I have removed it and run some retests - I cannot reproduce the hang at this point with my config
>>>
>>> I am going to run a defconfig and compare the results to see if this will give me any insights on the root cause.
>> I can reproduce on both my build machine (8 core) and my laptop (4 core).
>> If it helps I can share the rootfs.
>>
>> On my laptop I was able to reproduce within 5 minutes.
>> 1. make defconfig ARCH=um
>> 2. make -j 4 linux ARCH=um
>> 3. ./linux ubda=../Downloads/Debian-Squeeze-AMD64-root_fs mem=1G
>> 4. login to tty0
>> 5. wait a few minutes
>> 6. try to run top, it will hang in nanosleep
> 
> Pretty much the same. Does not hang, multiple test runs. Userspace is a relatively full install of a debian jessie.
> 
> I ran deconfig and did a diff. The prime suspect differences between my config and defconfig are stack order 3 (not 1) and io sched of cfq, not deadline.
> 
> I am going to retest just with these first to see if one of them is the culprit, if that does not make a difference, run it with defconfig and try to reproduce the hang.

I'm pretty sure that you don't see the issue as your Jessy userspace uses nanosleep periodically.

Thanks,
//richard

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