Re: [Xen-devel] [PATCH 06/23] libxl: init: libxl__poller_init and _get take gc

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [PATCH 06/23] libxl: init: libxl__poller_init and 
_get take gc"):
> On Tue, 2013-12-17 at 18:35 +0000, Ian Jackson wrote:
> > @@ -1622,7 +1617,7 @@ libxl__ao *libxl__ao_create(libxl_ctx *ctx, uint32_t 
> > domid,
> >      if (how) {
> >          ao->how = *how;
> >      } else {
> > -        ao->poller = libxl__poller_get(ctx);
> > +        ao->poller = libxl__poller_get(&ao->gc);
> 
> this is a bit subtle, libxl__poller_get would previously have gotten the
> toplevel ctx gc and not the ao-gc, if it had thought to init a GC at
> all.

Yes.

> It only actually uses whatever it gets for logging, so that's ok, but
> I'm not sure which would be the correct/expected gc to use. I take it
> you considered this?

Indeed.

> libxl__poller_get does a NOGC allocation and the associated manual
> memory mgmt -- now that it has the ao->gc in hand could it use that? Is
> the poller's lifecycle entirely contained within the ao?

No, it isn't.  The poller is longer-lived, mainly as a way to avoid
having to recreate the pipe on each occasion.

Ian.

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