netdev - Re: [Xen-devel] [RFC PATCH] xen-netback: fix error handling on netback

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Message-ID: <20160915141004.GM15958@citrix.com>
Date:   Thu, 15 Sep 2016 15:10:04 +0100
From:   Wei Liu <wei.liu2@...rix.com>
To:     Filipe Manco <filipe.manco@...lab.eu>
CC:     Wei Liu <wei.liu2@...rix.com>, <netdev@...r.kernel.org>,
        Xen-devel <xen-devel@...ts.xenproject.org>
Subject: Re: [Xen-devel] [RFC PATCH] xen-netback: fix error handling on
 netback_probe()

On Thu, Sep 15, 2016 at 04:05:17PM +0200, Filipe Manco wrote:
> On 14-09-2016 12:10, Wei Liu wrote:
> >CC xen-devel as well.
> >
> >On Tue, Sep 13, 2016 at 02:11:27PM +0200, Filipe Manco wrote:
> >>In case of error during netback_probe() (e.g. an entry missing on the
> >>xenstore) netback_remove() is called on the new device, which will set
> >>the device backend state to XenbusStateClosed by calling
> >>set_backend_state(). However, the backend state wasn't initialized by
> >>netback_probe() at this point, which will cause and invalid transaction
> >>and set_backend_state() to BUG().
> >>
> >>Initialize the backend state at the beginning of netback_probe() to
> >>XenbusStateInitialising, and create a new valid state transaction on
> >>set_backend_state(), from XenbusStateInitialising to XenbusStateClosed.
> >>
> >>Signed-off-by: Filipe Manco <filipe.manco@...lab.eu>
> >There is a state machine right before set_backend_state. You would also
> >need to update that.
> Good point I'll update the diagram.
> 
> After looking at the diagram and for consistency, shouldn't the transition
> Initialising -> InitWait be handled using set_backend_state()? Currently it
> is done directly in netback_probe() code. If you agree I'll submit a v2 with
> these two changes.

That's fine with me.

Wei.