Re: [Xen-devel] [patch]Make xend to take care of dead qemu-dm process

["Jean Guyader" <jean.guyader@xxxxxxxxx>]

Hi,

On Thu, Jul 17, 2008 at 9:00 AM, shawn <xiaowei.hu@xxxxxxxxxx> wrote:
> Hi Ian,
>
> I have some question now.
> 1.For each hvm guest there will be a separate qemu-dm process created,so
> we need to track multi opened named pipes.If use blocked read,does that
> mean I have to fork a new child in xend for each hvm guest when it was
> created?

You could use a select to watch every named pipes opened in Xend.

>
> 2.If I have to fork childs in xend, Could I kill the corresponding
> domain in this child process directly?
>
> thanks
> xiaowei
>
>
> On Thu, 2008-05-29 at 10:23 +0800, shawn wrote:
>> Hi Ian,
>>
>> Thanks for your explanation:)
>> Imporving this patch
>>
>> regards,
>> xiaowei
>>
>> On Wed, 2008-05-28 at 10:37 +0100, Ian Jackson wrote:
>> > shawn writes ("Re: [Xen-devel] [patch]Make xend to take care of dead 
>> > qemu-dm process"):
>> > > Could I ask if there is any methodology mistakes to solve this problem?
>> > > or need I keep improving this patch?
>> >
>> > I made some suggestions in a recent pair of messages in the thread
>> > `c/s 17731 portability issues'.  Did you not receive those messages ?
>> > >From over here they appear to have been copied to you as the author of
>> > the errant patch.
>> >
>> > Anyway, let me repeat myself:
>> >
>> > Certainly running ps in this way is not the right way to do it.
>> >
>> > Since qemu-dm is started by xend, it is quite possible for xend to
>> > have a better and more reliable arrangement for detecting termination
>> > of the qemu-dm process.  No polling is needed (and thus failure
>> > detection can be immediate).
>> >
>> > I suggested a design involving a named pipe.  qemu-dm would be passed
>> > the writing end across exec but just keep it, and not write anything
>> > to it.  xend would keep the reading end, and when it becomes readable
>> > would collect the qemu-dm exit status with waitpid (with W_NOHANG).
>> > xend would then kill the domain and report the fact of termination and
>> > also qemu-dm's exit status if available.
>> >
>> > On restart, xend would attempt to open the fifo again with
>> > O_RDONLY|O_NONBLOCK which would fail EWOUDLBLOCK if qemu-dm was no
>> > longer running; if it was still running then termination can be
>> > detected as above, although the exit status won't be recoverable.
>> >
>> > Does this all make sense ?  I'd be happy to expand on it if you'd like
>> > to ask questions.  We'll make sure to review your next submission
>> > thoroughly.
>> >
>> > Ian.
>>
>>
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>
>
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-- 
Jean Guyader

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