On 24/08/18 13:12, Jiri Slaby wrote: > On 07/30/2018, 10:18 AM, Xiao Liang wrote: >> On 07/29/2018 11:30 PM, David Miller wrote: >>> From: Xiao Liang <xili...@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?
How could it? Either the thread is waiting on module_unload_q _or_ on module_load_q. It can't wait on two queues at the same time. > 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)? To me this looks just wrong. A thread waiting on module_load_q won't be woken up again. I'd drop module_load_q in favor of module_unload_q. Juergen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
