Re: [Xen-devel] [PATCH 16/19] libxl: suspend: Abolish usleeps in domain suspend wait

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [PATCH 16/19] libxl: suspend: Abolish usleeps in 
domain suspend wait"):
> On Tue, 2014-03-04 at 14:56 +0000, Ian Jackson wrote:
> > Replace the use of a loop with usleep().
...
> > +    rc = libxl__ev_xswatch_register(gc, &dss->guest_watch,
> > +                                    suspend_common_wait_guest_watch,
> > +                                    "@releaseDomain");
> > +    if (rc) goto err;
> > +
> > +    rc = libxl__ev_time_register_rel(gc, &dss->guest_timeout, 
> > +                                     suspend_common_wait_guest_timeout,
> > +                                     60*1000);
> 
> This smells a lot like the xswait stuff you introduced towards the
> beginning of the series.
> 
> Is the difference just that you cannot read the "path" @releaseDomain?

Precisely.

> If so can we paper over that somehow in the helper?

Not without complicating its interface, I think.  We would really want
to prevent the @releaseDomain "path" being read at all.

I guess we could special-case paths starting with "@", the way
xenstore does, and always return ENOENT.  I'm not sure whether this
wrinkle (which would end up in the docs for the general facility) is
worth the saving in the one call site where it would be relevant.

Ian.

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