fix otg serial and networking tests (Bugfix)

[stanley31huang]

Description

Fix OTG test scripts for following issues

• add retries to remove kernel modules
• initial serial server on RPYC server side
• wait 2 seconds for the networking initialization

Resolved issues

Documentation

Tests

https://certification.canonical.com/hardware/202309-32027/submission/420194/

[baconYao]

See my inline suggestion

[baconYao]

I assume modules is just a straightforward list of module names—is that right? If so, I refactored the code below to make it easier to maintain and more intuitive.

Suggested change

	cp_modules = copy.deepcopy(modules)
	i = 0
	while i <= 3 and cp_modules:
	for module in modules:
	if module not in cp_modules:
	continue
	cmd = "modprobe -r {}".format(module)
	logging.info("Removing %s module", module)
	logging.info("$ %s", cmd)
	ret = subprocess.run(cmd, shell=True)
	if ret.returncode == 0:
	cp_modules.remove(module)
	i += 1
	if cp_modules:
	raise RuntimeError(
	"failed to remove modules: {}".format(cp_modules)
	if not modules:
	logging.info("No need to remove any OTG module since no candidate be provided")
	return
	retry_failed_set = set()
	# Go through each module
	for module in modules:
	max_retry_count = 3
	while max_retry_count:
	cmd = "modprobe -r {}".format(module)
	logging.info("Removing %s module", module)
	logging.info("$ %s", cmd)
	try:
	ret = subprocess.run(cmd, shell=True)
	if ret.returncode == 0:
	break
	max_retry_count -= 1
	if max_retry_count == 0:
	retry_failed_set.add(module)
	except subprocess.CalledProcessError as e:
	logging.warning("Command failed:", e)
	if retry_failed_set:
	raise RuntimeError(
	"Failed to remove modules: {}".format(retry_failed_set)

[stanley31huang]

yes, that's just a list of module name. But there're some dependencies between them, and you have to remove them in specific order. Otherwise, you won't be able to remove all of them.

let's said the list is usb_f_rndis, g_ether, usb_f_ecm, so the first module we would like to remove is usb_f_rndis, but we will get an error while we trying to remove it.

ubuntu@ubuntu:~$ lsmod  | grep libcom
libcomposite           77824  3 usb_f_rndis,g_ether,usb_f_ecm
ubuntu@ubuntu:~$ sudo modprobe -r usb_f_rndis
modprobe: FATAL: Module usb_f_rndis is in use.

So I use another mechansim to remove modules, I trying to remove all of modules at first round, and then do the same actions for rest of modules.

[baconYao]

Oh, I see. We have no idea of the modules' dependency and it causes this issue.

But it might be a risk if there are more than 3 modules and the have a dependency in a chain. For instance, four modules A, B, C, D and A depends on B, B depends C depends on D (A -> B -> C -> D). D will be removed in the first round, C will be removed in the second round, then B in third round, but will never remove A since we hardcode the iteration count as 3. I suggest we can use the count of modules we passed in as the retry count.