[Qemu-devel] Re: [libvirt] Re: [PATCH 2/3] Introduce monitor 'wait' command

Avi Kivity avi at redhat.com
Thu Apr 9 08:24:05 UTC 2009

Paul Brook wrote:
> No you don't. If you use event flags rather than discrete events then you 
> don't need to buffer at all. You just need to be able to store the state of 
> each type of event you're going to raise, which should be a bounded set.
> This has its own set of issues - typically race conditions or "lost" events if 
> the client (libvirt) code isn't written carefully, and means you can't attach 
> information with an event, only indicate that something happened.
> However if the correct model is used (event driven polling rather than purely 
> event driven) this shouldn't be problem.

I agree.  Every event notification should be readable with an info 
command.  The best way to enforce it is to have the event just say 
'something changed' and force the management app to issue an info 
command to find out what exactly.

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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