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gh-87135: Hang non-main threads that attempt to acquire the GIL during finalization (GH-105805)

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Instead of surprise crashes and memory corruption, we now hang threads that attempt to re-enter the Python interpreter after Python runtime finalization has started. These are typically daemon threads (our long standing mis-feature) but could also be threads spawned by extension modules that then try to call into Python. This marks the `PyThread_exit_thread` public C API as deprecated as there is no plausible safe way to accomplish that on any supported platform in the face of things like C++ code with finalizers anywhere on a thread's stack. Doing this was the least bad option.

Co-authored-by: Gregory P. Smith <greg@krypto.org>
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Jeremy Maitin-Shepard 2024-10-02 09:17:49 -07:00 • committed by GitHub
parent 113b2d7583
commit 8cc5aa47ee
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10 changed files with 247 additions and 29 deletions
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21
Include/pythread.h
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@ -17,7 +17,26 @@ typedef enum PyLockStatus {
PyAPI_FUNC(void) PyThread_init_thread(void);
PyAPI_FUNC(unsigned long) PyThread_start_new_thread(void (*)(void *), void *);
PyAPI_FUNC(void) _Py_NO_RETURN PyThread_exit_thread(void);
/* Terminates the current thread. Considered unsafe.
*
* WARNING: This function is only safe to call if all functions in the full call
* stack are written to safely allow it. Additionally, the behavior is
* platform-dependent. This function should be avoided, and is no longer called
* by Python itself. It is retained only for compatibility with existing C
* extension code.
*
* With pthreads, calls `pthread_exit` causes some libcs (glibc?) to attempt to
* unwind the stack and call C++ destructors; if a `noexcept` function is
* reached, they may terminate the process. Others (macOS) do unwinding.
*
* On Windows, calls `_endthreadex` which kills the thread without calling C++
* destructors.
*
* In either case there is a risk of invalid references remaining to data on the
* thread stack.
*/
Py_DEPRECATED(3.14) PyAPI_FUNC(void) _Py_NO_RETURN PyThread_exit_thread(void);
PyAPI_FUNC(unsigned long) PyThread_get_thread_ident(void);
#if (defined(__APPLE__) || defined(__linux__) || defined(_WIN32) \