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From: Ian Campbell <Ian.Campbell@citrix.com>
To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: Fwd: Re: [PATCH v3 3/5] libxl: call hotplug scripts from libxl for vbd
Date: Thu, 26 Apr 2012 14:09:22 +0100	[thread overview]
Message-ID: <1335445762.28015.141.camel@zakaz.uk.xensource.com> (raw)
In-Reply-To: <20377.18296.235567.918003@mariner.uk.xensource.com>

On Thu, 2012-04-26 at 14:02 +0100, Ian Jackson wrote:
> Thanks for your reply.  I see you didn't reply to all of my comments.
> Do you plan to address the others later ?
> 
> Roger Pau Monne writes ("Fwd: Re: [Xen-devel] [PATCH v3 3/5] libxl: call hotplug scripts from libxl for vbd"):
> > Ian Jackson escribió:
> > > So we no longer have any function which will synchronously and
> > > immediately destroy a domain and throw away everything to do with it.
> > > Is it actually the case that you think such a function cannot be
> > > provided ?
> > 
> > It can be provided, but we should create another command or add an
> > option to "destroy" (like -f), that doesn't wait for backend
> > disconnection and just nukes both frontend/backend xenstore entries.
> > This will also prevent us from executing hotplug scripts, and could lead
> > to unexpected results.
> 
> Quite so.  But it is important to be able to disregard a
> malfunctioning driver domain.  That would make it possible to shut
> down all the guests using it, destroy the driver domain itself, and
> restart it in a hopefully good state, for example.
> 
> > With this series we wait for the backend to disconnect for 10s, and if
> > it doesn't respond we nuke the frontend and wait for another 10s. If
> > after that it fails to disconnect we nuke the remaining backend xenstore
> > entries.
> 
> I think we need to think about these timeouts.  At the very least
> they're policy which should probably not be hardcoded in libxl; and
> arguably people might want to be able to specify infinite ("I trust my
> guest or driver domain and never want to pull the rug out from under
> its feet") or zero ("this guest or driver domain has gone wrong and I
> want it killed, now").

Unless the same is going to be true of the eventual solution (which I
suppose it may well be?) we should be wary of over engineering the
interim solution for 4.2.

> > >> +# Hack to prevent the execution of hotplug scripts from udev if the domain
> > >> +# has been launched from libxl
> > >> +if [ -n "${HOTPLUG_GATE}" ]&&  \
> > >> +   `xenstore-read "$HOTPLUG_GATE">/dev/null 2>&1`; then
> > >> +    exit 0
> > >> +fi
> > >
> > > Oh I see.  Hmm.  Why should this string not be fixed ?  I'm not sure I
> > > like the idea of being able to pass some random other xenstore path.
> > 
> > Anyway, I will have to pass an environmental variable when calling the
> > script from udev, I can rename this to UDEV_CALL=1 if that sounds better.
> 
> Perhaps it would be better to do things the other way around, and have
> an env var for the case where we're _not_ calling the script from
> udev ?  After all, udev config is configuration (at least on my
> distros) which the user may not update when the software is updated.

It was my suggestion to do it this way so that we don't end up with a
vestigial env var which must always be set for no real reason after
we've removed the udev path altogether.

I don't really mind though, we could live with that vestigial thing, or
have another, easier, transition a few releases down the line.

Ian.


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  reply	other threads:[~2012-04-26 13:09 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-20 13:23 [PATCH v3 0/5] libxl: call hotplug scripts from libxl Roger Pau Monne
2012-04-20 13:23 ` [PATCH v3 1/5] libxl: allow libxl__exec to take a parameter containing the env variables Roger Pau Monne
2012-04-23 15:37   ` Ian Jackson
2012-04-20 13:23 ` [PATCH v3 2/5] libxl: add libxl__xs_path_cleanup Roger Pau Monne
2012-04-23 15:33   ` Ian Jackson
2012-04-23 15:42     ` Roger Pau Monne
2012-04-23 16:49       ` Ian Jackson
2012-04-23 16:52   ` Ian Jackson
2012-04-25 13:19     ` Roger Pau Monne
2012-05-02  9:44     ` Roger Pau Monne
2012-04-20 13:23 ` [PATCH v3 3/5] libxl: call hotplug scripts from libxl for vbd Roger Pau Monne
2012-04-23 16:48   ` Ian Jackson
2012-04-24  9:16     ` Ian Campbell
2012-04-24 10:09       ` Ian Jackson
2012-04-24 10:17         ` Ian Campbell
2012-04-24 10:27           ` Ian Jackson
2012-04-24 10:29             ` Ian Campbell
2012-04-24 10:37               ` Ian Jackson
2012-04-25 13:53                 ` Roger Pau Monne
2012-04-25 14:59                   ` Ian Campbell
     [not found]     ` <4F982F18.2080902@citrix.com>
2012-04-26 11:48       ` Fwd: " Roger Pau Monne
2012-04-26 12:06         ` Ian Campbell
2012-04-26 12:12           ` Roger Pau Monne
2012-04-26 13:02         ` Ian Jackson
2012-04-26 13:09           ` Ian Campbell [this message]
2012-05-11 16:06             ` Ian Jackson
2012-05-11 16:26               ` Ian Campbell
2012-04-20 13:23 ` [PATCH v3 4/5] libxl: call hotplug scripts from libxl for vif Roger Pau Monne
2012-04-23 16:59   ` Ian Jackson
2012-04-24  9:18     ` Ian Campbell
2012-04-25 11:19   ` Ian Campbell
2012-04-25 11:24     ` Roger Pau Monne
2012-04-20 13:23 ` [PATCH v3 5/5] libxl: add "downscript=no" to Qemu call Roger Pau Monne
2012-04-23 15:38   ` Ian Jackson
2012-04-23 12:12 ` [PATCH v3 0/5] libxl: call hotplug scripts from libxl Marek Marczykowski
2012-04-23 13:31   ` Roger Pau Monne
2012-04-23 13:47     ` Marek Marczykowski
2012-04-23 13:59       ` Non-dom0 block backends (was: Re: [PATCH v3 0/5] libxl: call hotplug scripts from libxl) Joanna Rutkowska
2012-04-23 14:02     ` [PATCH v3 0/5] libxl: call hotplug scripts from libxl Ian Campbell
2012-04-23 16:25       ` Roger Pau Monne
2012-04-24  9:18         ` Ian Campbell

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