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Re: [Xen-devel] [RFC PATCH] xen-netback: fix error handling on netback_probe()



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@xxxxxxxxx>
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.
According to the definition of XenbusStateInitialising, this patch looks
plausible to me.

Wei.

Filipe
---
  drivers/net/xen-netback/xenbus.c | 10 ++++++++++
  1 file changed, 10 insertions(+)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 6a31f2610c23..c0e5f6994d01 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -270,6 +270,7 @@ static int netback_probe(struct xenbus_device *dev,
be->dev = dev;
        dev_set_drvdata(&dev->dev, be);
+       be->state = XenbusStateInitialising;
sg = 1; @@ -515,6 +516,15 @@ static void set_backend_state(struct backend_info *be,
  {
        while (be->state != state) {
                switch (be->state) {
+               case XenbusStateInitialising:
+                       switch (state) {
+                       case XenbusStateClosed:
+                               backend_switch_state(be, XenbusStateClosed);
+                               break;
+                       default:
+                               BUG();
+                       }
+                       break;
                case XenbusStateClosed:
                        switch (state) {
                        case XenbusStateInitWait:
--
2.7.4

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