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Re: [Xen-devel] [PATCH 1/3] libxl: events: debugging output relating to ao's

Ian Campbell writes ("Re: [Xen-devel] [PATCH 1/3] libxl: events: debugging 
output relating to ao's"):
> On Wed, 2012-05-16 at 16:25 +0100, Ian Jackson wrote:
> > @@ -1437,6 +1446,8 @@ void 
> > libxl__ao_complete_check_progress_reports(libxl__egc *egc, libxl__ao *ao)
> >              /* don't bother with this if we're not in the event loop */
> >              libxl__poller_wakeup(egc, ao->poller);
> >      } else if (ao->how.callback) {
> > +        AO_GC;
> I'd prefer that we kept these sorts of magic infrastructure macro things
> at the tops of functions.

Right.  The reason I did that was because I didn't want to have to
reason about the possible validity of the gc throughout this function,
which after all is capable of destroying the ao.

But actually I don't need the gc (which is just as well), but only the
ctx.  The function already has a call to libxl__gc_owner in it.  So I
have instead moved that call to the top and now there is a ctx which
is valid throughout the function.

> > @@ -1507,6 +1532,8 @@ int libxl__ao_inprogress(libxl__ao *ao)
> >                  break;
> >              }
> >  
> > +            LOG(DEBUG,"ao %p: not ready, waiting",ao);
> This one is too verbose, with xl -vvv cr -c it spams the pygrub console
> every second making it unusable. Even before that point there is a good
> dozen of them printed out.

I will redo the patches so the debugging is off by default and needs
to be enabled at compile-time.

> I noticed that very little of this stuff ends up
> in /var/log/xen/xl-<NAME>.log. I'm not sure why though since it would
> seem the obvious place for it to go. I guess it happens in the
> foreground not the daemon?

Yes.  Arguably -c should redirect the log to the logfile, or perhaps
xl should always copy all the log output to the logfile.  (But note
that xl itself has various output functions which do not use xtl.)


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