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gh-117300: Use stop the world to make sys._current_frames and sys._current_exceptions thread-safe. (#117301)

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This adds a stop the world pause to make the two functions thread-safe
when the GIL is disabled in the free-threaded build.

Additionally, the main test thread may call `sys._current_exceptions()` as
soon as `g_raised.set()` is called. The background thread may not yet reach
the `leave_g.wait()` line.
This commit is contained in:
Sam Gross 2024-03-29 15:33:06 -04:00 • committed by GitHub
parent 94c97423a9
commit 01bd74eadb
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2 changed files with 6 additions and 1 deletions
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3
Lib/test/test_sys.py
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@ -562,7 +562,8 @@ def g456():
# And the next record must be for g456(). # And the next record must be for g456().
filename, lineno, funcname, sourceline = stack[i+1] filename, lineno, funcname, sourceline = stack[i+1]
self.assertEqual(funcname, "g456") self.assertEqual(funcname, "g456")
self.assertTrue(sourceline.startswith("if leave_g.wait(")) self.assertTrue((sourceline.startswith("if leave_g.wait(") or
sourceline.startswith("g_raised.set()")))
finally: finally:
# Reap the spawned thread. # Reap the spawned thread.
leave_g.set() leave_g.set()

4
Python/pystate.c
View file

@ -2408,6 +2408,7 @@ _PyThread_CurrentFrames(void)
* Because these lists can mutate even when the GIL is held, we * Because these lists can mutate even when the GIL is held, we
* need to grab head_mutex for the duration. * need to grab head_mutex for the duration.
*/ */
_PyEval_StopTheWorldAll(runtime);
HEAD_LOCK(runtime); HEAD_LOCK(runtime);
PyInterpreterState *i; PyInterpreterState *i;
for (i = runtime->interpreters.head; i != NULL; i = i->next) { for (i = runtime->interpreters.head; i != NULL; i = i->next) {
@ -2441,6 +2442,7 @@ _PyThread_CurrentFrames(void)
done: done:
HEAD_UNLOCK(runtime); HEAD_UNLOCK(runtime);
_PyEval_StartTheWorldAll(runtime);
return result; return result;
} }
@ -2472,6 +2474,7 @@ _PyThread_CurrentExceptions(void)
* Because these lists can mutate even when the GIL is held, we * Because these lists can mutate even when the GIL is held, we
* need to grab head_mutex for the duration. * need to grab head_mutex for the duration.
*/ */
_PyEval_StopTheWorldAll(runtime);
HEAD_LOCK(runtime); HEAD_LOCK(runtime);
PyInterpreterState *i; PyInterpreterState *i;
for (i = runtime->interpreters.head; i != NULL; i = i->next) { for (i = runtime->interpreters.head; i != NULL; i = i->next) {
@ -2504,6 +2507,7 @@ _PyThread_CurrentExceptions(void)
done: done:
HEAD_UNLOCK(runtime); HEAD_UNLOCK(runtime);
_PyEval_StartTheWorldAll(runtime);
return result; return result;
} }