fix(usbdevice): close closed channel exception

[Yu-Jack]

Problem:

Reproduce Steps

1. Plug in USB device A.
2. Unplug USB device A and plug it in again. This increases the device number.
3. Create a usbdeviceclaim.
4. Reboot the host.
5. Observe that the device number of USB device A is reset to the value from step 1.
6. Delete the usbdeviceclaim.
7. Observe the error from pcidevices-controller: close closed channel.

In this cause, the original usbdeviceclaim won't work due to device number changed. That's expected.

However, the plugin.deregistered channel is closed twice due to multiple calls to ListAndWatch. But, I cannot find the root cause yet. Check #86 (comment)

bug.mp4

Solution:

Do not use close, just make it buffered channel.

Related Issue:

harvester/harvester#5762

Test plan:

Follow above steps, it shouldn't complain the same error.

resolved.mp4

[WebberHuang1118]

LGTM, thanks, do we need a separate issue for tracking the root cause?

[Yu-Jack]

@ibrokethecloud @WebberHuang1118

I find the root cause, it's quite straightforward.

We're trying to open gRPC server, and close it after error happens. Each time we start the gRPC server, kubelete invokes ListAndWatch function.

But, the program is stuck here since it didn't receive any value from that two channels.

done := false
for !done {
	select {
	case <-plugin.update:
		if err := sendUpdate(plugin.devicesToKubeVirtDevicePlugin()); err != nil {
			return err
		}
	case <-plugin.stop:
		done = true
}

So, I'll add new channel which presents that the gRPC server is closed or not. Please check my latest commits to see the changes, thanks!

[WebberHuang1118]

LGTM, thanks.

[ibrokethecloud]

lgtm. thanks.