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

[Richard Weinberger <richard@nod.at>]

Am 31.10.2015 um 16:10 schrieb Thomas Meyer:
> Am Samstag, den 31.10.2015, 14:54 +0100 schrieb Richard Weinberger:
>> On Thu, Oct 29, 2015 at 7:23 AM, Anton Ivanov
>> <anton.ivanov@kot-begemot.co.uk> wrote:
>>> I got the first patchset to build, it works very well on a single
>>> core
>>> host or with CPU pinning of the UML - the performance gain is >
>>> 25%.
>>>
>>> However, I introduced a race somewhere along the way - it crashes
>>> UML
>>> reliably if you do not pin CPUs.
>>
>> How does the crash look like?
>> I see also an issue with that patch, after UML has an uptime of a few
>> minutes
>> a task which does nanosleep() will never wake up.
>>
>> [<000000006001a29d>] __switch_to+0x53/0x82
>> [<00000000602995d2>] __schedule+0x2f4/0x3f7
>> [<0000000060299751>] schedule+0x7c/0x95
>> [<000000006029b871>] do_nanosleep+0x8b/0x134
>> [<0000000060068a41>] hrtimer_nanosleep+0xb2/0x15a
>> [<0000000060068b90>] SyS_nanosleep+0xa7/0xbf
>> [<000000006001d492>] handle_syscall+0x6a/0x84
>> [<00000000600304a8>] userspace+0x3d8/0x463
>> [<000000006001a180>] fork_handler+0x85/0x87
>> [<ffffffffffffffff>] 0xffffffffffffffff
>>
> 
> Hi, 
> 
> is this crash/hang about the "switch clocksource to hrtimers" patch or
> about the next patch that improves UBD improvements?

Whoops. Forgot to mention. "switch clocksource to hrtimers" is the bad one.
So far I can trigger the issue only by starting UML and waiting some time.

Thanks,
//richard


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