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From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Julien Grall <julien@xen.org>
Cc: <xen-devel@lists.xenproject.org>, Wei Liu <wl@xen.org>,
	Anthony PERARD <anthony.perard@citrix.com>,
	Juergen Gross <jgross@suse.com>,
	James Dingwall <james-xen@dingwall.me.uk>,
	Wei Liu <wei.liu@kernel.org>, Paul Durrant <paul@xen.org>
Subject: Re: [PATCH] libxl: force netback to wait for hotplug execution before connecting
Date: Tue, 25 Jan 2022 17:09:21 +0100	[thread overview]
Message-ID: <YfAgsat9NY+I0WAA@Air-de-Roger> (raw)
In-Reply-To: <8644d37a-49aa-8d9f-03ea-955d97a1cc28@xen.org>

On Tue, Jan 25, 2022 at 03:32:16PM +0000, Julien Grall wrote:
> Hi,
> 
> On 24/01/2022 16:02, Roger Pau Monne wrote:
> > By writing an empty "hotplug-status" xenstore node in the backend path
> > libxl can force Linux netback to wait for hotplug script execution
> > before proceeding to the 'connected' state.
> 
> I was actually chasing the same issue today :).
> 
> > 
> > This is required so that netback doesn't skip state 2 (InitWait) and
> 
> Technically netback never skip state 2 (otherwise it would always be
> reproducible). Instead, libxl may not be able to observe state 2 because
> receive a watch is asynchronous and doesn't contain the value of the node.
> So the backend may have moved to Connected before the state is read.

Right, might be more accurate to say it skips waiting for hotplug
script execution, and thus jumps from state 2 into 4. Note I think
it's also possible that by the time we setup the watch in libxl the
state has already been set to 4.

Thanks, Roger.


  reply	other threads:[~2022-01-25 16:10 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-24 16:02 [PATCH] libxl: force netback to wait for hotplug execution before connecting Roger Pau Monne
2022-01-25 14:02 ` Durrant, Paul
2022-01-25 15:32 ` Julien Grall
2022-01-25 16:09   ` Roger Pau Monné [this message]
2022-01-25 18:10     ` Julien Grall
2022-01-25 19:59 ` Wei Liu

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