what a correct use for virConnectDomainEventRegisterAny API, how to Obtain a stable expected result

[thomas.kuang]

Daniel, thanks for your help.


If it cannot receive a stable expected callback, it need a timer to handle the timeout, in the timer timeout to release memory passed to  virConnectDomainEventRegisterAny
or, maybe memory-leak now ...





At 2020-04-14 18:00:49, "Daniel P. Berrangé" <berrange at redhat.com> wrote:
>On Mon, Apr 13, 2020 at 05:32:38PM +0800, thomas.kuang wrote:
>> HI, everyone:
>> 
>> 
>> My target  deal with network hotplug use virDomainDetachDeviceFlags. Because when the API return ,the network maybe doesn’t remove from my vm guest os.
>> 
>> So I use virConnectDomainEventRegisterAny  to register an event ID: VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED ,
>> 
>>  my process as follow:
>> 
>> cb_para->call_id=virConnectDomainEventRegisterAny(cb_para->conn,cb_para->dom,VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED, VIR_DOMAIN_EVENT_CALLBACK(vnf_control_del_network_cb), cb_para, vnf_control_del_network_cb_free); 
>> 
>> 
>> 
>>     flags |= VIR_DOMAIN_AFFECT_CONFIG;
>>     if (virDomainIsActive(dom) == 1) {
>>         flags |= VIR_DOMAIN_AFFECT_LIVE;
>>     }
>> 
>>     ret = virDomainDetachDeviceFlags(dom, xml, flags);
>> 
>> 
>>  
>> 
>> above code write in thread loop ,then in the same loop :
>> 
>>  
>> 
>>        while (1) {
>> 
>>               mission = vnf_mission_queue_get(task);
>> 
>>               if (mission == NULL) {
>> 
>>                      sleep(1);
>> 
>>                      continue;
>> 
>>               } 
>> 
>>               vnf_op_process(&mission->info); // this will deal with network hotplug,will call virConnectDomainEventRegisterAny  then call  virDomainDetachDeviceFlags
>> 
>>               if (mission) {
>> 
>>                      vnf_mission_free(mission);
>> 
>>               } 
>> 
>>               if(virEventRunDefaultImpl() < 0) { // at here process  the registered callback for event-registered
>> 
>>                     printf();....
>> 
>> 
>>               }     
>> 
>>        }
>> 
>> My problem is: some time  , the virEventRunDefaultImpl can trigger the
>> vnf_control_del_network_cb  callback ,but some time  there is nothing,
>> as if the VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED has lost.
>> what cause the Unpredictable behavior ?  what is a correct use for
>> virConnectDomainEventRegisterAny ?
>
>The virDomainDetachDeviceFlags API is asynchronous and requires a cooperative
>guest to complete. It merely injects an ACPI PCI unplug request to the guest
>OS.  If the guest OS doesn't honour this request (because it is in early
>bootup, or is in BIOS, or is crashed, or is configured to disable hotplug,
>or is maliciously not responding), then the device will never be unplugged,
>and so you'll never get an event.
>
>So the first thing for you todo is to validate that the device really is
>being unplugged in the guest OS, and in QEMU.
>
>To check QEMU run:
>
>  virsh qemu-monitor-command --hmp $GUEST "info pci"
>
>and look to see if the PCI device is still listed in the output.
>
>Regards,
>Daniel
>-- 
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