Disable the GIL by default

Lib/subprocess.py

@@ -345,8 +345,6 @@ def _args_from_interpreter_flags():
     # -X options
     if dev_mode:
         args.extend(('-X', 'dev'))
-    if sys.flags.nogil:
-        args.extend(('-X', 'nogil'))
     for opt in ('faulthandler', 'tracemalloc', 'importtime',
                 'showrefcount', 'utf8'):
         if opt in xoptions:

Lib/test/test_capi/test_misc.py

@@ -247,7 +247,7 @@ def test_return_null_without_error(self):
                 r'SystemError: <built-in function return_null_without_error> '
                     r'returned NULL without setting an exception\n'
                 r'\n'
-                r'Current thread.*:\n'
+                r'Stack.*:\n'
                 r'  File .*", line 6 in <module>\n')
         else:
             with self.assertRaises(SystemError) as cm:
@@ -281,7 +281,7 @@ def test_return_result_with_error(self):
                         r'function return_result_with_error> '
                         r'returned a result with an exception set\n'
                     r'\n'
-                    r'Current thread.*:\n'
+                    r'Stack.*:\n'
                     r'  File .*, line 6 in <module>\n')
         else:
             with self.assertRaises(SystemError) as cm:

Lib/test/test_concurrent_futures.py

@@ -485,9 +485,11 @@ def test_cancel_futures_wait_false(self):
         rc, out, err = assert_python_ok('-c', """if True:
             from concurrent.futures import ThreadPoolExecutor
             from test.test_concurrent_futures import sleep_and_print
+            import time
             if __name__ == "__main__":
                 t = ThreadPoolExecutor()
                 t.submit(sleep_and_print, .1, "apple")
+                time.sleep(0.01) # wait for thread to start sleep_and_print
                 t.shutdown(wait=False, cancel_futures=True)
             """)
         # Errors in atexit hooks don't change the process exit code, check

Lib/test/test_embed.py

@@ -427,7 +427,7 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         use_environment=0,
         utf8_mode=0,
         dev_mode=0,
-        disable_gil=0,
+        disable_gil=1,
         coerce_c_locale=0,
     )
 
@@ -443,7 +443,7 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'isolated': 0,
         'use_environment': 1,
         'dev_mode': 0,
-        'disable_gil': 0,
+        'disable_gil': 1,
 
         'install_signal_handlers': 1,
         'use_hash_seed': 0,

Python/initconfig.c

@@ -866,7 +866,7 @@ PyConfig_InitIsolatedConfig(PyConfig *config)
     config->use_environment = 0;
     config->user_site_directory = 0;
     config->dev_mode = 0;
-    config->disable_gil = 0;
+    config->disable_gil = 1;
     config->install_signal_handlers = 0;
     config->use_hash_seed = 0;
     config->faulthandler = 0;

Python/preconfig.c

@@ -280,7 +280,7 @@ _PyPreCmdline_Read(_PyPreCmdline *cmdline, const PyPreConfig *preconfig)
             cmdline->disable_gil = (strcmp(env, "0") == 0);
         }
         else {
-            cmdline->disable_gil = 0;
+            cmdline->disable_gil = 1;
         }
     }