https://github.com/python/cpython/commit/1a2e7a747540f74414e7c50556bcb2cc127... commit: 1a2e7a747540f74414e7c50556bcb2cc127e9d1c branch: main author: Donghee Na <donghee.na@python.org> committer: corona10 <donghee.na92@gmail.com> date: 2024-06-28T06:46:46+09:00 summary: gh-120837: Update _Py_DumpExtensionModules to be async-signal-safe (gh-121051) files: M Python/pylifecycle.c diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c index 9bbfa831db317b..39eaa86098b2e5 100644 --- a/Python/pylifecycle.c +++ b/Python/pylifecycle.c @@ -3035,6 +3035,30 @@ fatal_error_exit(int status) } } +static inline int +acquire_dict_lock_for_dump(PyObject *obj) +{ +#ifdef Py_GIL_DISABLED + PyMutex *mutex = &obj->ob_mutex; + if (_PyMutex_LockTimed(mutex, 0, 0) == PY_LOCK_ACQUIRED) { + return 1; + } + return 0; +#else + return 1; +#endif +} + +static inline void +release_dict_lock_for_dump(PyObject *obj) +{ +#ifdef Py_GIL_DISABLED + PyMutex *mutex = &obj->ob_mutex; + // We can not call PyMutex_Unlock because it's not async-signal-safe. + // So not to wake up other threads, we just use a simple atomic store in here. + _Py_atomic_store_uint8(&mutex->_bits, _Py_UNLOCKED); +#endif +} // Dump the list of extension modules of sys.modules, excluding stdlib modules // (sys.stdlib_module_names), into fd file descriptor. @@ -3062,13 +3086,18 @@ _Py_DumpExtensionModules(int fd, PyInterpreterState *interp) PyObject *stdlib_module_names = NULL; if (interp->sysdict != NULL) { pos = 0; - while (PyDict_Next(interp->sysdict, &pos, &key, &value)) { + if (!acquire_dict_lock_for_dump(interp->sysdict)) { + // If we cannot acquire the lock, just don't dump the list of extension modules. + return; + } + while (_PyDict_Next(interp->sysdict, &pos, &key, &value, NULL)) { if (PyUnicode_Check(key) && PyUnicode_CompareWithASCIIString(key, "stdlib_module_names") == 0) { stdlib_module_names = value; break; } } + release_dict_lock_for_dump(interp->sysdict); } // If we failed to get sys.stdlib_module_names or it's not a frozenset, // don't exclude stdlib modules. @@ -3080,7 +3109,11 @@ _Py_DumpExtensionModules(int fd, PyInterpreterState *interp) int header = 1; Py_ssize_t count = 0; pos = 0; - while (PyDict_Next(modules, &pos, &key, &value)) { + if (!acquire_dict_lock_for_dump(modules)) { + // If we cannot acquire the lock, just don't dump the list of extension modules. + return; + } + while (_PyDict_Next(modules, &pos, &key, &value, NULL)) { if (!PyUnicode_Check(key)) { continue; } @@ -3121,6 +3154,7 @@ _Py_DumpExtensionModules(int fd, PyInterpreterState *interp) _Py_DumpASCII(fd, key); count++; } + release_dict_lock_for_dump(modules); if (count) { PUTS(fd, " (total: ");