fix: register halt_irq PM ops to poll sockets during cooperative scheduler idle

[danbugs]

Summary

• Point both networking-py and python-agent-driver kraft.yaml at danbugs/unikraft:fix/net-poll-sleep, which registers a halt_irq PM ops callback so the cooperative scheduler's idle thread polls sockets via __hl_sleep instead of spinning
• Add urllib_get_no_timeout.py CI test that exercises urlopen() without an explicit timeout — the code path used by mxc that currently hangs on Windows

Key kernel changes (in danbugs/unikraft:fix/net-poll-sleep)

• Remove dead uk_lcpu_halt_irq from plat/hyperlight/x86/lcpu.c (was shadowed by lib/uklcpu/lcpu.c)
• Register halt_irq PM ops in plat/hyperlight/shutdown.c that calls time_block_until() — polls sockets via __hl_sleep from the scheduler's idle thread
• Re-register after uk_boot_early_init() in setup.c so the native platform's HLT-based halt_irq doesn't overwrite it

Context

When urllib.request.urlopen() is called without an explicit timeout, Python never sets SO_RCVTIMEO/SO_SNDTIMEO. The cooperative scheduler's idle thread then calls uk_lcpu_halt_irq() which was a no-op spinwait — sockets were never polled, so the connection hung indefinitely. This fix makes the idle thread poll sockets, matching the behavior when timeouts are set.

Test plan

• urllib_get_no_timeout.py passes on Linux
• urllib_get_no_timeout.py passes on Windows
• Existing networking tests unaffected

[Copilot]

Pull request overview

This PR adjusts the Hyperlight example builds to use a Unikraft branch that polls sockets during cooperative-scheduler idle (via halt_irq PM ops), and adds a regression test covering urllib.request.urlopen() without an explicit timeout (the path that previously hung due to lack of socket polling).

Changes:

• Point examples/networking-py and examples/python-agent-driver at danbugs/unikraft:fix/net-poll-sleep.
• Add urllib_get_no_timeout.py and include it in the networking-py rootfs.
• Extend CI (test-examples.yml) to run the new networking test on both Linux and Windows.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
examples/python-agent-driver/kraft.yaml	Switch Unikraft source/version to the branch containing the halt_irq socket-polling fix.
examples/networking-py/kraft.yaml	Switch Unikraft source/version to the branch containing the halt_irq socket-polling fix.
examples/networking-py/urllib_get_no_timeout.py	New urllib GET test that omits timeout= to exercise the previously-hanging code path.
examples/networking-py/Dockerfile	Include the new test script in the example rootfs.
.github/workflows/test-examples.yml	Run the new networking test in CI on Linux and Windows.

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[github-actions]

Linux Benchmarks

Details

Benchmark suite	Current: 7bed20f	Previous: 682ad20	Ratio
hello_world (median)	20 ms	20 ms	1
pandas (median)	110 ms	120 ms	0.92
density (per VM)	8 MB	8 MB	1
snapshot (disk)	654 MiB	653 MiB	1.00

This comment was automatically generated by workflow using github-action-benchmark.

[github-actions]

Windows Benchmarks

Details

Benchmark suite	Current: 7bed20f	Previous: 682ad20	Ratio
hello_world (median)	284 ms	291 ms	0.98
pandas (median)	920 ms	1024 ms	0.90
density (per VM)	7 MB	7 MB	1
snapshot (disk)	661 MiB	661 MiB	1

This comment was automatically generated by workflow using github-action-benchmark.