Memray's test suite fails due to a deadlock with Textual 0.67.1

[godlygeek]

Memray's test suite fails due to a deadlock with Textual 0.67.1

[godlygeek]

Sorry, yep, I can confirm it's fixed. And we've switched to TEXTUAL_PRESS as well, so hopefully our tests are more robust in the future.

[pablogsal]

And then running the tree reporter on that capture file in a subprocess:

You may need to execute this command a couple of times until it reproduces (it looks like some kind of race).

[godlygeek]

Ah! It's now reproducing for me on Linux. I swear it wasn't before, but thank heavens for small favors. Previously I tried reproducing it with an existing virtualenv, but it reproduced after creating a new one. pip list shows:

Package                 Version
----------------------- -------
asttokens               2.4.1
coverage                7.5.3
Cython                  3.0.10
decorator               5.1.1
executing               2.0.1
greenlet                3.0.3
iniconfig               2.0.0
ipython                 8.25.0
jedi                    0.19.1
Jinja2                  3.1.4
linkify-it-py           2.0.3
markdown-it-py          3.0.0
MarkupSafe              2.1.5
matplotlib-inline       0.1.7
mdit-py-plugins         0.4.1
mdurl                   0.1.2
memray                  1.12.0
packaging               24.0
parso                   0.8.4
pexpect                 4.9.0
pip                     24.0
pkgconfig               1.5.5
pluggy                  1.5.0
prompt_toolkit          3.0.46
ptyprocess              0.7.0
pure-eval               0.2.2
Pygments                2.18.0
pytest                  8.2.2
pytest-cov              5.0.0
pytest-textual-snapshot 0.4.0
rich                    13.7.1
setuptools              65.5.0
six                     1.16.0
stack-data              0.6.3
syrupy                  4.6.1
textual                 0.67.1
traitlets               5.14.3
typing_extensions       4.12.1
uc-micro-py             1.0.3
wcwidth                 0.2.13

[godlygeek]

Adding some debugging to the rlock acquires:

diff --git a/src/textual/rlock.py b/src/textual/rlock.py
index d7a6af2d5..e1acce7fc 100644
--- a/src/textual/rlock.py
+++ b/src/textual/rlock.py
@@ -1,6 +1,10 @@
 from __future__ import annotations

 from asyncio import Lock, Task, current_task
+import datetime
+import traceback
+
+textual_log = open("/tmp/textual.log", "w")


 class RLock:
@@ -16,9 +20,12 @@ class RLock:
         task = current_task()
         assert task is not None
         if self._owner is None or self._owner is not task:
+            print(f"\n{datetime.datetime.now().isoformat()} Acquiring {self} at:", file=textual_log)
+            traceback.print_stack(limit=5, file=textual_log)
             await self._lock.acquire()
             self._owner = task
         self._count += 1
+        print(f"\n{datetime.datetime.now().isoformat()} Lock {self} acquired with count={self._count}", file=textual_log)

     def release(self) -> None:
         """Release a previously acquired lock."""
@@ -28,6 +35,7 @@ class RLock:
         if self._count < 0:
             # Should not occur if every acquire as a release
             raise RuntimeError("RLock.release called too many times")
+        print(f"\n{datetime.datetime.now().isoformat()} Lock {self} released, new count={self._count}", file=textual_log)
         if self._owner is task:
             if not self._count:
                 self._owner = None

and filtering out the locks that were acquired and then successfully released shows these 3 interesting events, the last one happening immediately before a hang of App.CLOSE_TIMEOUT seconds:

2024-06-12T14:27:53.508720 Acquiring <textual.rlock.RLock object at 0x7f6469f4b290> at:
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/app.py", line 1572, in run_async
    await app._shutdown()
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/app.py", line 2788, in _shutdown
    await self._close_all()
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/app.py", line 2763, in _close_all
    async with self._dom_lock:
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/rlock.py", line 51, in __aenter__
    await self.acquire()
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/rlock.py", line 24, in acquire
    traceback.print_stack(limit=5, file=textual_log)

2024-06-12T14:27:53.509372 Lock <textual.rlock.RLock object at 0x7f6469f4b290> acquired with count=1

2024-06-12T14:27:53.509662 Acquiring <textual.rlock.RLock object at 0x7f6468d92050> at:
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/widget.py", line 1130, in recompose
    async with self.batch():
  File "/opt/bb/lib/python3.11/contextlib.py", line 210, in __aenter__
    return await anext(self.gen)
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/widget.py", line 3487, in batch
    async with self.lock:
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/rlock.py", line 51, in __aenter__
    await self.acquire()
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/rlock.py", line 24, in acquire
    traceback.print_stack(limit=5, file=textual_log)

2024-06-12T14:27:53.510188 Lock <textual.rlock.RLock object at 0x7f6468d92050> acquired with count=1

2024-06-12T14:27:53.514009 Acquiring <textual.rlock.RLock object at 0x7f6469f4b290> at:
  File "/opt/bb/lib/python3.11/asyncio/events.py", line 84, in _run
    self._context.run(self._callback, *self._args)
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/app.py", line 3356, in prune_widgets_task
    await self._prune_nodes(widgets)
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/app.py", line 3383, in _prune_nodes
    async with self._dom_lock:
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/rlock.py", line 51, in __aenter__
    await self.acquire()
  File "/tmp/memray-issue/lib/python3.11/site-packages/textual/rlock.py", line 24, in acquire
    traceback.print_stack(limit=5, file=textual_log)

So:

1. App._close_all acquires self._dom_lock
2. Widget.recompose (for the Footer widget) acquires self.lock (a different lock), but never releases it
3. App._prune_nodes tries to acquire self._dom_lock and blocks, because the task calling App._close_all never released it

[godlygeek]

OK, here's a minimal reproducer for the issue:

Create a crash_reproducer.py with these contents:

from textual.app import App
from textual.binding import Binding
from textual.widgets import Footer


class MyApp(App[None]):
    BINDINGS = [
        Binding(key="q", action="quit", description="Quit the app"),
    ]

    def compose(self):
        yield Footer()


app = MyApp()
app.run()

And then run it with a "q" passed to stdin:

echo q | python crash_reproducer.py

[willmcgugan]

Thanks for doing the legwork on this. Looking at it now.

[willmcgugan]

In the meantime, an alternative to piping stdin is to use the TEXTUAL_PRESS env var to simulate keys.

TEXTUAL_PRESS=q python crash_reproducer.py

This is probably better in a test environment, because when stdin is not a tty it can subtly change how the app behaves.

[willmcgugan]

Please try Textual 0.68.0

[willmcgugan]

Closing, assumed fix.

[github-actions]

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