Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH] xen-netfront: wait xenbus state change when load module manually | From | Jiri Slaby <> | Date | Fri, 24 Aug 2018 13:12:52 +0200 |
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On 07/30/2018, 10:18 AM, Xiao Liang wrote: > On 07/29/2018 11:30 PM, David Miller wrote: >> From: Xiao Liang <xiliang@redhat.com> >> Date: Fri, 27 Jul 2018 17:56:08 +0800 >> >>> @@ -1330,6 +1331,11 @@ static struct net_device >>> *xennet_create_dev(struct xenbus_device *dev) >>> netif_carrier_off(netdev); >>> xenbus_switch_state(dev, XenbusStateInitialising); >>> + wait_event(module_load_q, >>> + xenbus_read_driver_state(dev->otherend) != >>> + XenbusStateClosed && >>> + xenbus_read_driver_state(dev->otherend) != >>> + XenbusStateUnknown); >>> return netdev; >>> exit: >> What performs the wakeups that will trigger for this sleep site? > In my understanding, backend leaving closed/unknow state can trigger the > wakeups. I mean to make sure both sides are ready for creating connection.
While backporting this to 4.12, I was surprised by the commit the same as Boris and David.
So I assume the explanation is that wake_up_all of module_unload_q in netback_changed wakes also all the processes waiting on module_load_q? If so, what makes sure that module_unload_q is queued and the process is the same as for module_load_q?
To me, it looks rather error-prone. Unless it is erroneous now, at least for future changes. Wouldn't it make sense to wake up module_load_q along with module_unload_q in netback_changed? Or drop module_load_q completely and use only module_unload_q (i.e. in xennet_create_dev too)?
thanks, -- js suse labs
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