[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net v5 1/1] xen-netback: Handle backend state transitions in a more robust way
On Thu, 2013-09-26 at 11:51 +0100, Paul Durrant wrote: > > -----Original Message----- > > From: Ian Campbell > > Sent: 26 September 2013 11:17 > > To: Paul Durrant > > Cc: xen-devel@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Wei Liu; David Vrabel > > Subject: Re: [PATCH net v5 1/1] xen-netback: Handle backend state > > transitions in a more robust way > > > > On Wed, 2013-09-25 at 10:59 +0100, Paul Durrant wrote: > > > When the frontend state changes netback now specifies its desired state > > to > > > a new function, set_backend_state(), which transitions through any > > > necessary intermediate states. > > > This fixes an issue observed with some old Windows frontend drivers > > where > > > they failed to transition through the Closing state and netback would not > > > behave correctly. > > > > I'm somewhat terrified of breaking compatibility with some old or > > obscure frontend here. I don't think it is reasonable to try and test > > all of those so I guess we'll just have to deal with that when it > > happens... > > > > > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx> > > > Cc: Ian Campbell <ian.campbell@xxxxxxxxxx> > > > Cc: Wei Liu <wei.liu2@xxxxxxxxxx> > > > Cc: David Vrabel <david.vrabel@xxxxxxxxxx> > > > --- > > > drivers/net/xen-netback/xenbus.c | 143 > > ++++++++++++++++++++++++++++++-------- > > > 1 file changed, 113 insertions(+), 30 deletions(-) > > > > > > diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen- > > netback/xenbus.c > > > index a53782e..01329b2 100644 > > > --- a/drivers/net/xen-netback/xenbus.c > > > +++ b/drivers/net/xen-netback/xenbus.c > > > @@ -24,6 +24,7 @@ > > > struct backend_info { > > > struct xenbus_device *dev; > > > struct xenvif *vif; > > > + enum xenbus_state state; > > > > This cannot just be read from xenstore because of the > > wait-for-hotplug-script deferral stuff, right? > > > > Yes, that's right. > > > I'm not sure it is worth clarifying that, either by a comment or by > > naming it deferred_state_change or something? > > > > Itâs the xenbus state that's deferred, the backend state leads so I > could name it 'desired_state' or 'target_state' perhaps; probably a > bit ugly so I'll add a comment above that field I think. OK. > > > > -static void destroy_backend(struct xenbus_device *dev) > > > +static void backend_connect(struct backend_info *be) > > > { > > > - struct backend_info *be = dev_get_drvdata(&dev->dev); > > > + if (be->vif) > > > + connect(be); > > > +} > > > > > > - if (be->vif) { > > > - kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE); > > > - xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status"); > > > - xenvif_free(be->vif); > > > - be->vif = NULL; > > > > Where did this uevent offlining functionality end up? > > > > It's done in netback_remove() . > > > > +static inline void backend_switch_state(struct backend_info *be, > > > + enum xenbus_state state) > > > +{ > > > + struct xenbus_device *dev = be->dev; > > > + > > > + pr_debug("%s -> %s\n", dev->nodename, xenbus_strstate(state)); > > > + be->state = state; > > > + > > > + /* If we are waiting for a hotplug script then defer the > > > + * actual xenbus state change. > > > > Is the right/wise regardless of the state we are moving too? Might the > > state change have effectively "cancelled" the need to wait for the > > script? > > > > The previous code only deferred when moving to Connected. If we are now > > moving to Closed/Closing do we still need to wait? > > > > I debated about this; we never really dealt with this before. I think > it's legitimate for the frontend to give up waiting for a backend > hotplug so we should be able to go from InitWait to Closing, so in > this case be->state will be Closing when the script (hopefully) > finishes. Thus we move to that when the watch fires rather than to > Connected. Then the frontend can move to Closed. If the hotplug script > never finishes then I don't think we're any more screwed than we were > before. OK. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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