Re: [Xen-devel] Sched_op hypercall small questions

[Daniel Castro <evil.dani@xxxxxxxxx>]

On Tue, Sep 20, 2011 at 6:08 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 20.09.11 at 10:31, Daniel Castro <evil.dani@xxxxxxxxx> wrote:
>> On Tue, Sep 20, 2011 at 4:33 PM, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>>> Daniel Castro  09/20/11 8:18 AM >>>
>>>>On Tue, Sep 20, 2011 at 2:41 PM, Keir Fraser  wrote:
>>>>> On 19/09/2011 22:21, "Daniel Castro"  wrote:
>>>>>
>>>>>> Greetings all.
>>>>>>
>>>>>> Some small question regarding schedule poll operation hypercall.
>>>>>>
>>>>>> 1. struct sched_poll poll.timeout is measured in what unit of time?
>>>>>> Secs, ms? ns?
>>>>>
>>>>> It is an absolute system time (rather than a duration), in nanoseconds.
>>>>
>>>>really an absolute system time?
>>>>
>>>>When the timeout is set and the timeout is reached, the system behaves
>>>>like if the event had been received? i.e the bit is changed?
>>>
>>> No, the bit would remain unset - the poll times out then, it doesn't
>>> "complete".
>>
>> My Guest VM would get stuck on the hypercall call, like if it was an
>> infinite loop?
>
> I'm not following. Of course, if you blindly and constantly re-issue the
> hypercall, then you'd be stuck in a loop. Allowing to prevent that is
> what the timeout is for.

What I am trying is writing to the xenstore ring, issue the send
hypercall, then wait (poll hypercall) for event, then read answer from
ring.

The waiting is not working, but If I wait enough time, the ring will
contain the answer, but apparently I have a problem with my event
channel port. So to test this theory I am using event channel status
hypercall, and I get:
Status 2 (meaning interdomain connected)
VCPU 0
The Union reports dom 32752 and port 2.

Right now, there are two things that jump to my mind, first when I
issue the poll hypercall the system continues execution, instead of
yielding CPU unitl event arrives. If it were never to arrive it should
yield infinitely, right?
Second, the bit is never set. Or it is being undone before I can check it.

Thanks,

Daniel

>
>> And once the timeout occurs or the event get delivered, then the
>> hypercall would return, right?
>
> Yes.
>
> Jan
>
>



-- 
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| +---------------------------------+ | This space intentionally blank
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| |   | Daniel Castro,                |
| |   | Consultant/Programmer.|
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