add unit test

Author: LindaSummer

Lib/test/test_free_threading/test_gc.py

@@ -1,7 +1,7 @@
 import unittest
 
 import threading
-from threading import Thread
+from threading import Barrier, Thread
 from unittest import TestCase
 import gc
 
@@ -94,6 +94,34 @@ def evil():
         thread.start()
         thread.join()
 
+    def test_set_threshold(self):
+        # GH-148613: Setting the GC threshold from another thread could causes
+        # race between the `gc_should_collect` and `gc_set_threshold` functions.
+        NUM_THREADS = 8
+        NUM_ITERS = 100_000
+        barrier = Barrier(NUM_THREADS)
+
+        class CyclicReference:
+            def __init__(self):
+                self.r = self
+
+        def allocator():
+            barrier.wait()
+            for _ in range(NUM_ITERS):
+                CyclicReference()
+
+        def setter():
+            barrier.wait()
+            for i in range(NUM_ITERS):
+                gc.set_threshold(100 + (i % 100), 10 + (i % 10), 10 + (i % 10))
+
+        threads = [Thread(target=allocator) for _ in range(NUM_THREADS - 1)]
+        threads.append(Thread(target=setter))
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join()
+
 
 if __name__ == "__main__":
     unittest.main()

Modules/gcmodule.c

@@ -167,12 +167,12 @@ gc_set_threshold_impl(PyObject *module, int threshold0, int group_right_1,
         gcstate->generations[2].threshold = threshold2;
     }
 #else
-    _Py_atomic_exchange_int(&gcstate->young.threshold, threshold0);
+    _Py_atomic_store_int(&gcstate->young.threshold, threshold0);
     if (group_right_1) {
-        _Py_atomic_exchange_int(&gcstate->old[0].threshold, threshold1);
+        _Py_atomic_store_int(&gcstate->old[0].threshold, threshold1);
     }
     if (group_right_2) {
-        _Py_atomic_exchange_int(&gcstate->old[1].threshold, threshold2);
+        _Py_atomic_store_int(&gcstate->old[1].threshold, threshold2);
     }
 #endif
     Py_RETURN_NONE;

Python/gc_free_threading.c

@@ -1665,7 +1665,7 @@ void
 _PyGC_InitState(GCState *gcstate)
 {
     // TODO: move to pycore_runtime_init.h once the incremental GC lands.
-    _Py_atomic_exchange_int(&gcstate->young.threshold, 2000);
+    gcstate->young.threshold = 2000;
 }