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

[shawn <xiaowei.hu@xxxxxxxxxx>]

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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