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From: Clemens Kolbitsch <clemens.kol@gmx.at>
Subject: Re: Re: [Qemu-devel] qcow2 vs. image file format --> pci device
Date: Mon, 1 Oct 2007 10:52:27 +0200
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To: qemu-devel@nongnu.org
Cc: dor.laor@gmail.com

> Clemens Kolbitsch wrote:
> > hi everyone!
> > i have a strange problem (at least to me it seems strange :-)  ):
> >
> > i have implemented a pci device (Network IC) and it works just fine when
> > using a standard image. however i now want to support snapshotting...
> >
> > i started to convert my image into the qcow2 format and suddenly my code
> > does not work any more... even if i uncomment everything that has to do
> > with snapshotting in my code, it still blocks during qemu startup.
> >
> > the thing that could cause this: i use 2 additional threads in my NIC
> > code ... each is working with semaphores that might cause problems.
> >
> > is there something in particular i have to be careful of when using qcow2
> > file format?
> >
> > thanks!!
>
> Qcow2 uses async io which triggers io completion with SIGIO signal.
> If you use threads you must mask this (and also SIGALARM, ..) so your
> thread won't
> take over the main threads handling.
> Anyway, using threads is not the standard qemu guideline.

Hi,
Ok.. thanks! How do I tell Qemu that I use threads (in this case I don't see 
an easy way around using them... although there is one obviously ;-) )??

In what other HW example can I see how to use the SIGIO completion stuff?
Clemens