Re: [libvirt] any better way to treat device-detach timeout ?
After rethinking, I guess there's still a problem:
Suggest that
1 the device got detached in qemu after 10 secs,
2 the func virDomainDetachDeviceFlags() has already returned success in the 5th second.
Libvirt won't wait for the DEVICE_DELETED event after then.
3 the 'def' has the device untouched
4 thus, 10 secs later, the device is detached successfully in qemu, but libvirt has the
device un-detached in def(transient XML).
Which means that: libvirt is not correct in device list then, we will fail to
attach/detach that device after then.
Oscar.
>
>On Fri, Mar 11, 2016 at 07:40:54 +0000, Zhangbo (Oscar) wrote:
>> Hi,all:
>>
>> I find that we remove devices only after DEVICE_DELETED
>event.(patch:3fbf78bd).
>> And it treats TIMEOUT as success. The detailed codes are shown as
>below:
>> rc = qemuDomainWaitForDeviceRemoval(vm);
>> if (rc == 0 || rc == 1)
>> ret = qemuDomainRemoveDiskDevice(driver, vm, detach);
>> else
>> ret = 0;
>>
>>
>> Here comes the problem:
>> If
>> 1. We pass
>flags=3(VIR_DOMAIN_AFFECT_LIVE|VIR_DOMAIN_AFFECT_CONFIG) to
>virDomainDetachDeviceFlags,
>> 2. It timed out to receive DEVICE_DELETED event,
>virDomainDetachDeviceFlags api will return 0(succeed).
>> Please be aware that: vm->newdef(persistent) removes the device
>while vm->def(transient) keeps it untouched.
>> 3. Then we try to attach the same device with flag 3, because it differs in
>newDef and def, the API virDomainDetachDeviceFlags() returns ERROR.
>> Consequent attach/detach jobs all fail after then.
>>
>> So, shall we make it return FAIL when it fails in
>qemuDomainWaitForDeviceRemoval()?
>
>No.
>
>> Or just remove the device in def after we get the DEVICE_DELETED event?
>
>Yes, and we already do that. The API is explicitly documented as a
>request to detach a device. It returns 0 when this request was
>successfully passed to the guest OS. Some devices (e.g., USB devices)
>are detached immediately, but others may require guest cooperation and
>may take long time to detach or the guest may even completely ignore the
>request. Thus, once virDomainDetachDeviceFlags returns 0, you need to
>either periodically check the active XML to see if the device was
>removed or you can register a callback for
>VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED event which is emitted when
I got it! Thanks!
>libvirt
>really removes the device from the domain (after getting DEVICE_DELETED
>from QEMU).
>
>Jirka
>
>--
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