gh-116738: Make grp module thread-safe

Lib/test/support/threading_helper.py

@@ -248,3 +248,27 @@ def requires_working_threading(*, module=False):
             raise unittest.SkipTest(msg)
     else:
         return unittest.skipUnless(can_start_thread, msg)
+
+
+def run_concurrently(worker_func, args, nthreads):
+    """
+    Run the worker function concurrently in multiple threads.
+    """
+    barrier = threading.Barrier(nthreads)
+
+    def wrapper_func(*args):
+        # Wait for all threads to reach this point before proceeding.
+        barrier.wait()
+        worker_func(*args)
+
+    with catch_threading_exception() as cm:
+        workers = (
+            threading.Thread(target=wrapper_func, args=args)
+            for _ in range(nthreads)
+        )
+        with start_threads(workers):
+            pass
+
+        # If a worker thread raises an exception, re-raise it.
+        if cm.exc_value is not None:
+            raise cm.exc_value

Lib/test/test_free_threading/test_grp.py

@@ -0,0 +1,36 @@
+import unittest
+
+from test.support import import_helper, threading_helper
+from test.support.threading_helper import run_concurrently
+
+grp = import_helper.import_module("grp")
+
+from test import test_grp
+
+
+NTHREADS = 10
+
+
+@threading_helper.requires_working_threading()
+class TestGrp(unittest.TestCase):
+    def setUp(self):
+        self.test_grp = test_grp.GroupDatabaseTestCase()
+
+    def test_racing_test_values(self):
+        # test_grp.test_values() calls grp.getgrall() and checks the entries
+        run_concurrently(
+            worker_func=self.test_grp.test_values, args=(), nthreads=NTHREADS
+        )
+
+    def test_racing_test_values_extended(self):
+        # test_grp.test_values_extended() calls grp.getgrall(), grp.getgrgid(),
+        # grp.getgrnam() and checks the entries
+        run_concurrently(
+            worker_func=self.test_grp.test_values_extended,
+            args=(),
+            nthreads=NTHREADS,
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()

Lib/test/test_free_threading/test_heapq.py

@@ -3,10 +3,10 @@
 import heapq
 
 from enum import Enum
-from threading import Thread, Barrier
 from random import shuffle, randint
 
 from test.support import threading_helper
+from test.support.threading_helper import run_concurrently
 from test import test_heapq
 
 
@@ -28,7 +28,7 @@ def test_racing_heapify(self):
         heap = list(range(OBJECT_COUNT))
         shuffle(heap)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heapq.heapify, args=(heap,), nthreads=NTHREADS
         )
         self.test_heapq.check_invariant(heap)
@@ -40,7 +40,7 @@ def heappush_func(heap):
             for item in reversed(range(OBJECT_COUNT)):
                 heapq.heappush(heap, item)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heappush_func, args=(heap,), nthreads=NTHREADS
         )
         self.test_heapq.check_invariant(heap)
@@ -61,7 +61,7 @@ def heappop_func(heap, pop_count):
             # Each local list should be sorted
             self.assertTrue(self.is_sorted_ascending(local_list))
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heappop_func,
             args=(heap, per_thread_pop_count),
             nthreads=NTHREADS,
@@ -77,7 +77,7 @@ def heappushpop_func(heap, pushpop_items):
                 popped_item = heapq.heappushpop(heap, item)
                 self.assertTrue(popped_item <= item)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heappushpop_func,
             args=(heap, pushpop_items),
             nthreads=NTHREADS,
@@ -93,7 +93,7 @@ def heapreplace_func(heap, replace_items):
             for item in replace_items:
                 heapq.heapreplace(heap, item)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heapreplace_func,
             args=(heap, replace_items),
             nthreads=NTHREADS,
@@ -105,7 +105,7 @@ def test_racing_heapify_max(self):
         max_heap = list(range(OBJECT_COUNT))
         shuffle(max_heap)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heapq.heapify_max, args=(max_heap,), nthreads=NTHREADS
         )
         self.test_heapq.check_max_invariant(max_heap)
@@ -117,7 +117,7 @@ def heappush_max_func(max_heap):
             for item in range(OBJECT_COUNT):
                 heapq.heappush_max(max_heap, item)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heappush_max_func, args=(max_heap,), nthreads=NTHREADS
         )
         self.test_heapq.check_max_invariant(max_heap)
@@ -138,7 +138,7 @@ def heappop_max_func(max_heap, pop_count):
             # Each local list should be sorted
             self.assertTrue(self.is_sorted_descending(local_list))
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heappop_max_func,
             args=(max_heap, per_thread_pop_count),
             nthreads=NTHREADS,
@@ -154,7 +154,7 @@ def heappushpop_max_func(max_heap, pushpop_items):
                 popped_item = heapq.heappushpop_max(max_heap, item)
                 self.assertTrue(popped_item >= item)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heappushpop_max_func,
             args=(max_heap, pushpop_items),
             nthreads=NTHREADS,
@@ -170,7 +170,7 @@ def heapreplace_max_func(max_heap, replace_items):
             for item in replace_items:
                 heapq.heapreplace_max(max_heap, item)
 
-        self.run_concurrently(
+        run_concurrently(
             worker_func=heapreplace_max_func,
             args=(max_heap, replace_items),
             nthreads=NTHREADS,
@@ -214,27 +214,6 @@ def create_random_list(a, b, size):
         """
         return [randint(-a, b) for _ in range(size)]
 
-    def run_concurrently(self, worker_func, args, nthreads):
-        """
-        Run the worker function concurrently in multiple threads.
-        """
-        barrier = Barrier(nthreads)
-
-        def wrapper_func(*args):
-            # Wait for all threads to reach this point before proceeding.
-            barrier.wait()
-            worker_func(*args)
-
-        with threading_helper.catch_threading_exception() as cm:
-            workers = (
-                Thread(target=wrapper_func, args=args) for _ in range(nthreads)
-            )
-            with threading_helper.start_threads(workers):
-                pass
-
-            # Worker threads should not raise any exceptions
-            self.assertIsNone(cm.exc_value)
-
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2025-06-12-00-03-34.gh-issue-116738.iBBAdo.rst

@@ -0,0 +1 @@
+Make methods in :mod:`grp` thread-safe on the :term:`free threaded <free threading>` build.

Modules/grpmodule.c

@@ -168,9 +168,16 @@ grp_getgrgid_impl(PyObject *module, PyObject *id)
 
     Py_END_ALLOW_THREADS
 #else
+    static PyMutex getgrgid_mutex = {0};
+    PyMutex_Lock(&getgrgid_mutex);
+    // The getgrgid() function need not be thread-safe.
+    // https://pubs.opengroup.org/onlinepubs/9699919799/functions/getgrgid.html
     p = getgrgid(gid);
 #endif
     if (p == NULL) {
+#ifndef HAVE_GETGRGID_R
+        PyMutex_Unlock(&getgrgid_mutex);
+#endif
         PyMem_RawFree(buf);
         if (nomem == 1) {
             return PyErr_NoMemory();
@@ -185,6 +192,8 @@ grp_getgrgid_impl(PyObject *module, PyObject *id)
     retval = mkgrent(module, p);
 #ifdef HAVE_GETGRGID_R
     PyMem_RawFree(buf);
+#else
+    PyMutex_Unlock(&getgrgid_mutex);
 #endif
     return retval;
 }
@@ -249,9 +258,16 @@ grp_getgrnam_impl(PyObject *module, PyObject *name)
 
     Py_END_ALLOW_THREADS
 #else
+    static PyMutex getgrnam_mutex = {0};
+    PyMutex_Lock(&getgrnam_mutex);
+    // The getgrnam() function need not be thread-safe.
+    // https://pubs.opengroup.org/onlinepubs/9699919799/functions/getgrnam.html
     p = getgrnam(name_chars);
 #endif
     if (p == NULL) {
+#ifndef HAVE_GETGRNAM_R
+        PyMutex_Unlock(&getgrnam_mutex);
+#endif
         if (nomem == 1) {
             PyErr_NoMemory();
         }
@@ -261,6 +277,9 @@ grp_getgrnam_impl(PyObject *module, PyObject *name)
         goto out;
     }
     retval = mkgrent(module, p);
+#ifndef HAVE_GETGRNAM_R
+    PyMutex_Unlock(&getgrnam_mutex);
+#endif
 out:
     PyMem_RawFree(buf);
     Py_DECREF(bytes);