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Re: [Xen-devel] [PATCH] Talk_to_backend on xenbus_probe only if drv->pro

To: Murillo Bernardes <mfb@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Talk_to_backend on xenbus_probe only if drv->probe was sucessful
From: Ewan Mellor <ewan@xxxxxxxxxxxxx>
Date: Thu, 15 Dec 2005 17:18:30 +0000
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On Thu, Dec 15, 2005 at 02:59:31PM -0200, Murillo Bernardes wrote:

> On Thursday 15 December 2005 11:38, Ewan Mellor wrote:
> > On Mon, Dec 12, 2005 at 04:35:45PM -0200, Murillo Bernardes wrote:
> > > Hi,
> > >
> > > This patch makes xenbus_probe only call talk_to_backend if drv->probe()
> > > was sucessful.
> > >
> > > There is no sense in add a watch before drv->probe, because if it fails
> > > the otherend_changed callback will be called and receive a struct with
> > > invalid pointers and we get a segfault (ooops).
> >
> > Applied, thanks Murillo.
> >
> > Ewan.
> I just found a problem on that. It breaks block devices! I don't know why yet.
> 
> Do you know why block devices rely on that watch before probe?

Yes, I found that one too!  blkback_probe calls alloc_blkif(dev->otherend_id),
so it doesn't need the watch, but it does need the otherend details to have
been read.  I'm applying another patch right now.

Ewan.

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