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gh-116167: Allow disabling the GIL with PYTHON_GIL=0 or -X gil=0 (#116338)

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In free-threaded builds, running with `PYTHON_GIL=0` will now disable the
GIL. Follow-up issues track work to re-enable the GIL when loading an
incompatible extension, and to disable the GIL by default.

In order to support re-enabling the GIL at runtime, all GIL-related data
structures are initialized as usual, and disabling the GIL simply sets a flag
that causes `take_gil()` and `drop_gil()` to return early.
This commit is contained in:
Brett Simmers 2024-03-11 11:02:58 -04:00 • committed by GitHub
parent 546eb7a3be
commit 2731913dd5
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GPG key ID: B5690EEEBB952194
12 changed files with 163 additions and 1 deletions
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45
Python/initconfig.c
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@ -95,6 +95,9 @@ static const PyConfigSpec PYCONFIG_SPEC[] = {
SPEC(safe_path, BOOL),
SPEC(int_max_str_digits, INT),
SPEC(cpu_count, INT),
#ifdef Py_GIL_DISABLED
SPEC(enable_gil, INT),
#endif
SPEC(pathconfig_warnings, BOOL),
SPEC(program_name, WSTR),
SPEC(pythonpath_env, WSTR_OPT),
@ -278,6 +281,9 @@ static const char usage_envvars[] =
"PYTHON_CPU_COUNT: Overrides the return value of os.process_cpu_count(),\n"
" os.cpu_count(), and multiprocessing.cpu_count() if set to\n"
" a positive integer.\n"
#ifdef Py_GIL_DISABLED
"PYTHON_GIL : When set to 0, disables the GIL.\n"
#endif
"PYTHONDEVMODE : enable the development mode.\n"
"PYTHONPYCACHEPREFIX: root directory for bytecode cache (pyc) files.\n"
"PYTHONWARNDEFAULTENCODING: enable opt-in EncodingWarning for 'encoding=None'.\n"
@ -862,6 +868,9 @@ _PyConfig_InitCompatConfig(PyConfig *config)
config->_is_python_build = 0;
config->code_debug_ranges = 1;
config->cpu_count = -1;
#ifdef Py_GIL_DISABLED
config->enable_gil = _PyConfig_GIL_DEFAULT;
#endif
}
@ -1574,6 +1583,24 @@ config_wstr_to_int(const wchar_t *wstr, int *result)
return 0;
}
static PyStatus
config_read_gil(PyConfig *config, size_t len, wchar_t first_char)
{
#ifdef Py_GIL_DISABLED
if (len == 1 && first_char == L'0') {
config->enable_gil = _PyConfig_GIL_DISABLE;
}
else if (len == 1 && first_char == L'1') {
config->enable_gil = _PyConfig_GIL_ENABLE;
}
else {
return _PyStatus_ERR("PYTHON_GIL / -X gil must be \"0\" or \"1\"");
}
return _PyStatus_OK();
#else
return _PyStatus_ERR("PYTHON_GIL / -X gil are not supported by this build");
#endif
}
static PyStatus
config_read_env_vars(PyConfig *config)
@ -1652,6 +1679,15 @@ config_read_env_vars(PyConfig *config)
config->safe_path = 1;
}
const char *gil = config_get_env(config, "PYTHON_GIL");
if (gil != NULL) {
size_t len = strlen(gil);
status = config_read_gil(config, len, gil[0]);
if (_PyStatus_EXCEPTION(status)) {
return status;
}
}
return _PyStatus_OK();
}
@ -2207,6 +2243,15 @@ config_read(PyConfig *config, int compute_path_config)
config->show_ref_count = 1;
}
const wchar_t *x_gil = config_get_xoption_value(config, L"gil");
if (x_gil != NULL) {
size_t len = wcslen(x_gil);
status = config_read_gil(config, len, x_gil[0]);
if (_PyStatus_EXCEPTION(status)) {
return status;
}
}
#ifdef Py_STATS
if (config_get_xoption(config, L"pystats")) {
config->_pystats = 1;