test/hil: avoid parallel MTP probe races

test/hil/hil_test.py

@@ -39,6 +39,7 @@
 import argparse
 import io
 import itertools
+import math
 import os
 import random
 import re
@@ -64,7 +65,7 @@ _mp = multiprocessing.get_context('fork')
 Pool, Lock, Semaphore, Manager = _mp.Pool, _mp.Lock, _mp.Semaphore, _mp.Manager
 import hashlib
 import ctypes
-from pymtp import MTP
+from pymtp import LIBMTP_DeviceEntry, LIBMTP_RawDevice, MTP
 import string
 
 # --- per-board dev-session locks (see test/hil/board_lock.py) ------------
@@ -127,11 +128,11 @@ def enum_timeout() -> int:
     return _enum_timeout
 
 
-def wait_until(predicate, step: float = 1.0):
+def wait_until(predicate, step: float = 1.0, timeout: float | None = None):
     """Poll predicate under the per-attempt enum budget. Deadline-based so a slow predicate
-    body (subprocess, libmtp scan) counts against the budget. Returns the first truthy
-    predicate value, or None on timeout."""
-    deadline = time.monotonic() + enum_timeout()
+    body (subprocess, libmtp scan) counts against the budget. An explicit timeout overrides
+    that budget. Returns the first truthy predicate value, or None on timeout."""
+    deadline = time.monotonic() + (enum_timeout() if timeout is None else timeout)
     while True:
         r = predicate()
         if r:
@@ -503,23 +504,120 @@ def read_disk_file(uid: str, lun: int, fname: str) -> bytes:
     return data
 
 
-def open_mtp_dev(uid):
+def open_mtp_dev(uid: str):
     mtp = MTP()
+    last_usb = None
+    deadline = time.monotonic() + 2 * enum_timeout()
 
-    def try_open():
-        # unmount gio/gvfs MTP mount which blocks libmtp from accessing the device
-        subprocess.run(f"gio mount -u mtp://TinyUsb_TinyUsb_Device_{uid}/",
-                       shell=True, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
-        for raw in mtp.detect_devices():
-            mtp.device = mtp.mtp.LIBMTP_Open_Raw_Device(ctypes.byref(raw))
-            if mtp.device:
-                sn = mtp.get_serialnumber().decode('utf-8')
-                if sn == uid:
-                    return mtp
-                mtp.disconnect()
+    def find_usb():
+        nonlocal last_usb
+        for serial_fname in glob.glob('/sys/bus/usb/devices/*/serial'):
+            dev_path = Path(serial_fname).parent
+            try:
+                if (Path(serial_fname).read_text().strip().lower() != uid.lower()
+                        or (dev_path / 'idVendor').read_text().strip() != 'cafe'
+                        or (dev_path / 'idProduct').read_text().strip() != '4017'):
+                    continue
+                busnum = int((dev_path / 'busnum').read_text())
+                devnum = int((dev_path / 'devnum').read_text())
+                last_usb = (dev_path.name, busnum, devnum)
+                usb_node = Path('/dev/bus/usb') / f'{busnum:03d}' / f'{devnum:03d}'
+                if usb_node.exists():
+                    return dev_path, busnum, devnum
+            except (OSError, ValueError):
+                pass
         return None
 
-    return wait_until(try_open)
+    def remaining() -> float:
+        return max(0.0, deadline - time.monotonic())
+
+    target = wait_until(find_usb, step=0.05, timeout=remaining())
+    if target is None:
+        if last_usb:
+            name, busnum, devnum = last_usb
+            raise AssertionError(
+                f'MTP USB node not ready for {uid} at {name} ({busnum:03d}/{devnum:03d})')
+        raise AssertionError(f'MTP USB device not enumerated for {uid}')
+
+    dev_path, busnum, devnum = target
+    wait_seconds = max(1, math.ceil(remaining()))
+    try:
+        udev_wait = subprocess.run(
+            ['udevadm', 'wait', '--initialized=yes', f'--timeout={wait_seconds}', str(dev_path)],
+            capture_output=True, text=True, timeout=wait_seconds + 2)
+    except FileNotFoundError:
+        udev_wait = None
+    except subprocess.TimeoutExpired as e:
+        raise AssertionError(
+            f'udev initialization timed out for MTP {uid} at {busnum:03d}/{devnum:03d}') from e
+
+    if udev_wait is not None and udev_wait.returncode != 0:
+        try:
+            wait_help = subprocess.run(
+                ['udevadm', 'wait', '--help'], stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL, timeout=2)
+            wait_supported = wait_help.returncode == 0
+        except (FileNotFoundError, subprocess.TimeoutExpired):
+            wait_supported = False
+
+        if wait_supported:
+            detail = (udev_wait.stderr or udev_wait.stdout).strip().replace('\n', ' ')
+            detail = detail[-300:] or 'no diagnostic'
+            raise AssertionError(
+                f'udevadm wait failed for MTP {uid} at {busnum:03d}/{devnum:03d}: {detail}')
+        udev_wait = None
+
+    if udev_wait is None:
+        # systemd < 251 has no target-specific udev wait. Its libmtp rule creates
+        # this link only after synchronous mtp-probe has released the interface.
+        def find_libmtp_marker():
+            found = find_usb()
+            if found is None:
+                return None
+            found_path, found_busnum, found_devnum = found
+            marker = Path('/dev') / f'libmtp-{found_path.name}'
+            usb_node = Path('/dev/bus/usb') / f'{found_busnum:03d}' / f'{found_devnum:03d}'
+            if marker.exists() and marker.resolve() == usb_node:
+                return found
+            return None
+
+        target = wait_until(find_libmtp_marker, step=0.05, timeout=remaining())
+        if target is None:
+            raise AssertionError(
+                f'udevadm wait unsupported and libmtp marker absent for MTP {uid}; '
+                'install libmtp-runtime')
+        dev_path, busnum, devnum = target
+    elif find_usb() != target:
+        raise AssertionError(f'MTP USB device {uid} changed while waiting for udev initialization')
+
+    # A desktop GVFS session may claim MTP after udev probing. This is a no-op on
+    # headless runners, but preserves support for rigs where the mount exists.
+    try:
+        subprocess.run(['gio', 'mount', '-u', f'mtp://TinyUsb_TinyUsb_Device_{uid}/'],
+                       stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, timeout=2)
+    except (FileNotFoundError, subprocess.TimeoutExpired):
+        pass
+
+    # TinyUSB needs no libmtp device quirks. Construct its raw entry directly so
+    # this test never probes another MTP board that is still being initialized.
+    entry = LIBMTP_DeviceEntry(None, 0xcafe, None, 0x4017, 0)
+    raw = LIBMTP_RawDevice(entry, busnum, devnum)
+    mtp.device = mtp.mtp.LIBMTP_Open_Raw_Device(ctypes.byref(raw))
+    if not mtp.device:
+        raise AssertionError(f'libmtp could not open MTP {uid} at {busnum:03d}/{devnum:03d}')
+
+    try:
+        serial_raw = mtp.get_serialnumber()
+        serial = serial_raw.decode('utf-8') if serial_raw else ''
+        if serial.lower() != uid.lower():
+            raise AssertionError(f'MTP serial mismatch at {busnum:03d}/{devnum:03d}: {serial}')
+    except Exception:
+        try:
+            mtp.disconnect()
+        except Exception:
+            pass
+        raise
+    return mtp
 
 
 def get_printer_dev(id: str, vendor_str, product_str, ifnum: int):
@@ -1432,15 +1530,13 @@ def test_device_mtp(board):
     _null = os.open(os.devnull, os.O_WRONLY)
     os.dup2(_null, fd)
 
-    mtp = open_mtp_dev(uid)
-
-    # --- AFTER: restore stderr ---
-    os.dup2(_saved, fd)
-    os.close(_null)
-    os.close(_saved)
-
-    if mtp is None or mtp.device is None:
-        assert False, 'MTP device not found'
+    try:
+        mtp = open_mtp_dev(uid)
+    finally:
+        # --- AFTER: restore stderr ---
+        os.dup2(_saved, fd)
+        os.close(_null)
+        os.close(_saved)
 
     try:
         assert b"TinyUSB" == mtp.get_manufacturer(), 'MTP wrong manufacturer'