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Merged
ericsnowcurrently merged 17 commits into from
May 19, 2025
Merged

gh-128639: Don't assume one thread in subinterpreter finalization #128640

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025cc17
Fix subinterpreter cleanup.
ZeroIntensity Jan 8, 2025
eea3ba9
Add and fix tests.
ZeroIntensity Jan 8, 2025
149e0cf
Add blurb
ZeroIntensity Jan 8, 2025
1761c37
Fix threading tests.
ZeroIntensity Jan 8, 2025
8febfbf
Fix test_embed.
ZeroIntensity Jan 8, 2025
5a73ce1
Remove buggy test.
ZeroIntensity Jan 8, 2025
a7cc3fe
Skip flaky test.
ZeroIntensity Jan 8, 2025
7c44c0b
Add an assertion.
ZeroIntensity Feb 4, 2025
6551bfa
Remove stray newline.
ZeroIntensity Feb 5, 2025
f19e28d
Add another assertion.
ZeroIntensity Feb 5, 2025
02da72a
Merge branch 'main' into subinterpreter-thread-shutdown
ZeroIntensity Feb 7, 2025
a759540
Merge branch 'main' of https://github.com/python/cpython into subinte…
ZeroIntensity Mar 28, 2025
76e4ec9
Use new is_after_fork parameter
ZeroIntensity Mar 28, 2025
1555731
Apply suggestions from code review
ZeroIntensity May 19, 2025
d61099e
Move call to finalize_subinterpreters()
ZeroIntensity May 19, 2025
09851dc
Unskip the threading test.
ZeroIntensity May 19, 2025
b223396
Add a comment for the test.
ZeroIntensity May 19, 2025
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60 changes: 58 additions & 2 deletions Lib/test/test_interpreters/test_api.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -647,6 +647,59 @@ def test_created_with_capi(self):
self.interp_exists(interpid))


def test_remaining_threads(self):
r_interp, w_interp = self.pipe()

FINISHED = b'F'

# It's unlikely, but technically speaking, it's possible
# that the thread could've finished before interp.close() is
# reached, so this test might not properly exercise the case.
# However, it's quite unlikely and I'm too lazy to deal with it.
interp = interpreters.create()
interp.exec(f"""if True:
import os
import threading
import time

def task():
time.sleep(1)
os.write({w_interp},{FINISHED!r})

threads = [threading.Thread(target=task) for _ in range(3)]
for t in threads:
t.start()
""")
interp.close()

self.assertEqual(os.read(r_interp, 1), FINISHED)

def test_remaining_daemon_threads(self):
interp = _interpreters.create(
types.SimpleNamespace(
use_main_obmalloc=False,
allow_fork=False,
allow_exec=False,
allow_threads=True,
allow_daemon_threads=True,
check_multi_interp_extensions=True,
gil='own',
)
)
_interpreters.exec(interp, f"""if True:
import threading
import time

def task():
time.sleep(100)

threads = [threading.Thread(target=task, daemon=True) for _ in range(3)]
for t in threads:
t.start()
""")
_interpreters.destroy(interp)


class TestInterpreterPrepareMain(TestBase):

def test_empty(self):
Expand DownExpand Up@@ -756,7 +809,10 @@ def script():
spam.eggs()

interp = interpreters.create()
interp.exec(script)
try:
interp.exec(script)
finally:
interp.close()
""")

stdout, stderr = self.assert_python_failure(scriptfile)
Expand All@@ -765,7 +821,7 @@ def script():
# File "{interpreters.__file__}", line 179, in exec
self.assertEqual(stderr, dedent(f"""\
Traceback (most recent call last):
File "{scriptfile}", line 9, in <module>
File "{scriptfile}", line 10, in <module>
interp.exec(script)
~~~~~~~~~~~^^^^^^^^
{interpmod_line.strip()}
Expand Down
6 changes: 5 additions & 1 deletion Lib/test/test_interpreters/test_lifecycle.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -132,6 +132,7 @@ def test_sys_path_0(self):
'sub': sys.path[0],
}}, indent=4), flush=True)
""")
interp.close()
'''
# <tmp>/
# pkg/
Expand DownExpand Up@@ -172,7 +173,10 @@ def test_gh_109793(self):
argv = [sys.executable, '-c', '''if True:
from test.support import interpreters
interp = interpreters.create()
raise Exception
try:
raise Exception
finally:
interp.close()
''']
proc = subprocess.run(argv, capture_output=True, text=True)
self.assertIn('Traceback', proc.stderr)
Expand Down
5 changes: 1 addition & 4 deletions Lib/test/test_threading.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -1612,10 +1612,7 @@ def f():

_testcapi.run_in_subinterp(%r)
""" % (subinterp_code,)
with test.support.SuppressCrashReport():
rc, out, err = assert_python_failure("-c", script)
self.assertIn("Fatal Python error: Py_EndInterpreter: "
"not the last thread", err.decode())
assert_python_ok("-c", script)

def _check_allowed(self, before_start='', *,
allowed=True,
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-01-08-12-52-47.gh-issue-128640.9nbh9z.rst
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
Fix a crash when using threads inside of a subinterpreter.
9 changes: 6 additions & 3 deletions Programs/_testembed.c
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Expand Up@@ -1424,9 +1424,12 @@ static int test_audit_subinterpreter(void)
PySys_AddAuditHook(_audit_subinterpreter_hook, NULL);
_testembed_Py_InitializeFromConfig();

Py_NewInterpreter();
Py_NewInterpreter();
Py_NewInterpreter();
PyThreadState *tstate = PyThreadState_Get();
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@ZeroIntensityZeroIntensityJan 8, 2025

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I think this test working before was a fluke. Py_NewInterpreter changes the thread state, and I don't think we support calling Py_Finalize from a subinterpreter.

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@ericsnowcurrentlyericsnowcurrentlyMay 19, 2025

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It's probably okay but your change helps future-proof the test.

for (int i = 0; i < 3; ++i)
{
Py_EndInterpreter(Py_NewInterpreter());
PyThreadState_Swap(tstate);
}

Py_Finalize();

Expand Down
56 changes: 28 additions & 28 deletions Python/pylifecycle.c
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Original file line numberDiff line numberDiff line change
Expand Up@@ -1982,6 +1982,7 @@ resolve_final_tstate(_PyRuntimeState *runtime)
}
else{
/* Fall back to the current tstate. It's better than nothing. */
// XXX No it's not
main_tstate = tstate;
}
}
Expand DownExpand Up@@ -2027,6 +2028,16 @@ _Py_Finalize(_PyRuntimeState *runtime)

_PyAtExit_Call(tstate->interp);

/* Clean up any lingering subinterpreters.

Two preconditions need to be met here:

- This has to happen before _PyRuntimeState_SetFinalizing is
called, or else threads might get prematurely blocked.
- The world must not be stopped, as finalizers can run.
*/
finalize_subinterpreters();

assert(_PyThreadState_GET() == tstate);

/* Copy the core config, PyInterpreterState_Delete() free
Expand DownExpand Up@@ -2114,9 +2125,6 @@ _Py_Finalize(_PyRuntimeState *runtime)
_PyImport_FiniExternal(tstate->interp);
finalize_modules(tstate);

/* Clean up any lingering subinterpreters. */
finalize_subinterpreters();

/* Print debug stats if any */
_PyEval_Fini();

Expand DownExpand Up@@ -2400,9 +2408,8 @@ Py_NewInterpreter(void)
return tstate;
}

/* Delete an interpreter and its last thread. This requires that the
given thread state is current, that the thread has no remaining
frames, and that it is its interpreter's only remaining thread.
/* Delete an interpreter. This requires that the given thread state
is current, and that the thread has no remaining frames.
It is a fatal error to violate these constraints.

(Py_FinalizeEx() doesn't have these constraints -- it zaps
Expand DownExpand Up@@ -2432,14 +2439,15 @@ Py_EndInterpreter(PyThreadState *tstate)
_Py_FinishPendingCalls(tstate);

_PyAtExit_Call(tstate->interp);

if (tstate != interp->threads.head || tstate->next != NULL){
Py_FatalError("not the last thread");
}
_PyRuntimeState *runtime = interp->runtime;
_PyEval_StopTheWorldAll(runtime);
PyThreadState *list = _PyThreadState_RemoveExcept(tstate);

/* Remaining daemon threads will automatically exit
when they attempt to take the GIL (ex: PyEval_RestoreThread()). */
_PyInterpreterState_SetFinalizing(interp, tstate);
_PyEval_StartTheWorldAll(runtime);
_PyThreadState_DeleteList(list, /*is_after_fork=*/0);

// XXX Call something like _PyImport_Disable() here?

Expand DownExpand Up@@ -2470,6 +2478,8 @@ finalize_subinterpreters(void)
PyInterpreterState *main_interp = _PyInterpreterState_Main();
assert(final_tstate->interp == main_interp);
_PyRuntimeState *runtime = main_interp->runtime;
assert(!runtime->stoptheworld.world_stopped);
assert(_PyRuntimeState_GetFinalizing(runtime) == NULL);
struct pyinterpreters *interpreters = &runtime->interpreters;

/* Get the first interpreter in the list. */
Expand DownExpand Up@@ -2498,27 +2508,17 @@ finalize_subinterpreters(void)

/* Clean up all remaining subinterpreters. */
while (interp != NULL){
assert(!_PyInterpreterState_IsRunningMain(interp));

/* Find the tstate to use for fini. We assume the interpreter
will have at most one tstate at this point. */
PyThreadState *tstate = interp->threads.head;
if (tstate != NULL){
/* Ideally we would be able to use tstate as-is, and rely
on it being in a ready state: no exception set, not
running anything (tstate->current_frame), matching the
current thread ID (tstate->thread_id). To play it safe,
we always delete it and use a fresh tstate instead. */
assert(tstate != final_tstate);
_PyThreadState_Attach(tstate);
PyThreadState_Clear(tstate);
_PyThreadState_Detach(tstate);
PyThreadState_Delete(tstate);
/* Make a tstate for finalization. */
PyThreadState *tstate = _PyThreadState_NewBound(interp, _PyThreadState_WHENCE_FINI);
if (tstate == NULL){
// XXX Some graceful way to always get a thread state?
Py_FatalError("thread state allocation failed");
}
tstate = _PyThreadState_NewBound(interp, _PyThreadState_WHENCE_FINI);

/* Destroy the subinterpreter. */
/* Enter the subinterpreter. */
_PyThreadState_Attach(tstate);

/* Destroy the subinterpreter. */
Py_EndInterpreter(tstate);
assert(_PyThreadState_GET() == NULL);

Expand Down
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