linux-kernel - Re: [RFCv2 07/11] remoteproc: Register virtio devices after vring allocation

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Message-ID: <20121221134051.GB22252@WorkStation.localnet>
Date:	Fri, 21 Dec 2012 15:40:51 +0200
From:	Ido Yariv <ido@...ery.com>
To:	Sjur BRENDELAND <sjur.brandeland@...ricsson.com>
Cc:	Ohad Ben-Cohen <ohad@...ery.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sjur Brændeland <sjur@...ndeland.net>
Subject: Re: [RFCv2 07/11] remoteproc: Register virtio devices after vring
 allocation

Hi Sjur,

On Fri, Dec 21, 2012 at 01:20:02PM +0100, Sjur BRENDELAND wrote:
> Hi Ido,
> 
> > From: Ido Yariv [mailto:ido@...ery.com]
> > > Postpone the registration of virtio devices until all
> > > vritio ring resource has been allocated.
> > > This fixes the following bug: The driver's start callback
> > > is called before all vring notify ids are allocated and
> > > max_notifyid will be increased after starting the remoteproc.
> > 
> > It seems that this patch wont solve this issue, since
> > rproc_add_virtio_dev eventually increases max_notifyid, so the same
> > problem will simply occur at a later stage.
> > 
> > Also, it seems that the original rproc_add_virtio_dev calls were not
> > removed, so devices would be added twice.
> 
> Indeed. This was introduced by a faulty merge - I'll fix this up.
> 
> > If max_notifyid needs to be set before the first virtio device is added,
> > how about counting the number of notification ids in advance before
> > adding the devices, by traversing the resource list twice?
> 
> Ugh, thanks I missed this. How about calling rproc_alloc_vring from
> rproc_parse_vring so that the resource allocation are done before
> the virtio devices are started? 

I don't think that would solve it - rproc_parse_vring is called from
rproc_handle_vdev which is called more than once (for each vdev), so
max_notifyid could still be increased after the first call to
rproc_add_virtio_dev.

> BTW, I think most of the other review comments from you are OK. I'll
> try to address them in my next patch-set sometime early next year.

Great, thanks!
Happy new year :)

Ido.
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