From 1c613dc4b4545f9c352edf834cc039e0939dc1bf Mon Sep 17 00:00:00 2001
From: Abdessamad Derraz <3028866+Abdess@users.noreply.github.com>
Date: Tue, 27 Oct 2026 21:08:47 +0100
Subject: [PATCH] fix: take the probe lock per standalone run

standalone_probe now holds the host probe lock for one run, its load check included, as core_probe does, and the docs no longer wrap region_check or standalone_probe in flock.
---
 scripts/standalone_probe.py    |  7 +++++++
 tests/test_standalone_probe.py | 24 ++++++++++++++++++++++++
 wiki/tools.md                  | 10 +++++-----
 3 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/scripts/standalone_probe.py b/scripts/standalone_probe.py
index ac1e67a9d..9a945be15 100644
--- a/scripts/standalone_probe.py
+++ b/scripts/standalone_probe.py
@@ -510,6 +510,13 @@ def probe(args: argparse.Namespace) -> int:
         for problem in problems:
             print(f"ERROR: {problem}", file=sys.stderr)
         return 2
+    # One run on the host at a time, as core_probe: the lock is held for
+    # this run, its load check included, and freed when it ends.
+    with cp.host_probe_lock():
+        return _probe(args, emu)
+
+
+def _probe(args: argparse.Namespace, emu: Emulator) -> int:
     meta, tree = installed(emu, args.sha256)
     max_load = args.max_load if args.max_load is not None else (os.cpu_count() or 1) / 4
     load_before = cp.load_average()
diff --git a/tests/test_standalone_probe.py b/tests/test_standalone_probe.py
index 73763f648..6a51f731c 100644
--- a/tests/test_standalone_probe.py
+++ b/tests/test_standalone_probe.py
@@ -157,6 +157,30 @@ class Oracle(unittest.TestCase):
         self.assertEqual(result["verdicts"], {"absent": "bios_error", "scph5501.bin": "boots"})
 
 
+class HostLock(unittest.TestCase):
+    def test_a_run_holds_the_probe_lock_for_itself(self) -> None:
+        import contextlib
+        from unittest import mock
+
+        events = []
+
+        @contextlib.contextmanager
+        def lock():
+            events.append("take")
+            yield
+            events.append("free")
+
+        def body(_args, _emu):
+            events.append("run")
+            return 0
+
+        with tempfile.NamedTemporaryFile(suffix=".cue") as content, \
+                mock.patch.object(sp.cp, "host_probe_lock", lock), mock.patch.object(sp, "_probe", body):
+            args = sp.build_parser().parse_args(["run", "duckstation", "--content", content.name])
+            self.assertEqual(sp.probe(args), 0)
+        self.assertEqual(events, ["take", "run", "free"])
+
+
 class CommandLine(unittest.TestCase):
     def test_check_refuses_two_destinations(self) -> None:
         with tempfile.NamedTemporaryFile(suffix=".cue") as content:
diff --git a/wiki/tools.md b/wiki/tools.md
index cbcb32c4b..a9b205bb8 100644
--- a/wiki/tools.md
+++ b/wiki/tools.md
@@ -1098,7 +1098,7 @@ times, each a record whose subject is `region-<core>-<game>-<variant>`.
 | `pack` | the files of `generate_pack.py --emulator E --region R`, where the pack puts them |
 
 ```bash
-flock ~/.local/state/retrobios/probe.lock python scripts/region_check.py run \
+python scripts/region_check.py run \
   --emulator beetle_psx --system sony-playstation --core-name mednafen_psx
 python scripts/region_check.py report        # the outcome of every region record, as JSON
 ```
@@ -1120,7 +1120,7 @@ frame for a game, a variant counts as booting when it samples the same frames
 as the `full` run, and the outcome says it was judged that way. The system
 pages show each outcome as a sentence ("the Japanese BIOS boots the Japanese
 game, the other regions' BIOS do not") with links to the four records. A
-maintainer starts each run under the probe lock. Nothing runs by itself.
+maintainer starts each run. Each core_probe run takes the host probe lock for itself and frees it before the next, so do not wrap the command in `flock`. Nothing runs by itself.
 
 ### standalone_probe.py
 
@@ -1134,11 +1134,11 @@ sandbox, oracle and record functions, imported and not copied.
 ```bash
 python scripts/standalone_probe.py resolve duckstation   # the asset EmuDeck's installer picks
 python scripts/standalone_probe.py fetch duckstation     # download and unpack it, by sha256
-flock ~/.local/state/retrobios/probe.lock python scripts/standalone_probe.py run duckstation \
+python scripts/standalone_probe.py run duckstation \
   --content game.cue --content-label "Bust-A-Move 2 - Arcade Edition (USA)" \
   --bios-file scph5501.bin=bios/Sony/PlayStation/scph5501.bin \
   --samples 60 --interval 1.5 --require-sandbox --record
-flock ~/.local/state/retrobios/probe.lock python scripts/standalone_probe.py check pcsx2 \
+python scripts/standalone_probe.py check pcsx2 \
   --content game.bin --vary ps2-0230a-20080220.bin= \
   --vary "ps2-0230a-20080220.bin=bios/Sony/PlayStation 2/ps2-0230a-20080220.bin" \
   --claim "..." --method "..." --require-sandbox --record
@@ -1168,7 +1168,7 @@ Supported: DuckStation and PCSX2. Dolphin, Flycast, PPSSPP, melonDS, xemu and
 MAME are installed by EmuDeck from Flathub, Ryujinx from a Codeberg tarball and
 RPCS3 from its own update server: each needs its installer's rule before it
 can be added. Cemu is an AppImage like the two supported ones, and waits for
-Wii U content, which no catalog romfetch reads holds. A maintainer starts each run under the probe lock. Nothing runs
+Wii U content, which no catalog romfetch reads holds. Each run takes the host probe lock (`RETROBIOS_PROBE_LOCK`) for itself, its load check included, and frees it when it ends, as `core_probe.py` does. A maintainer starts each run. Nothing runs
 by itself.
 
 ### Other tools