gh-116738: use PyMutex in lzma module (#140711)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>

Lib/test/test_free_threading/test_lzma.py

@@ -0,0 +1,56 @@
+import unittest
+
+from test.support import import_helper, threading_helper
+from test.support.threading_helper import run_concurrently
+
+lzma = import_helper.import_module("lzma")
+from lzma import LZMACompressor, LZMADecompressor
+
+from test.test_lzma import INPUT
+
+
+NTHREADS = 10
+
+
+@threading_helper.requires_working_threading()
+class TestLZMA(unittest.TestCase):
+    def test_compressor(self):
+        lzc = LZMACompressor()
+
+        # First compress() outputs LZMA header
+        header = lzc.compress(INPUT)
+        self.assertGreater(len(header), 0)
+
+        def worker():
+            # it should return empty bytes as it buffers data internally
+            data = lzc.compress(INPUT)
+            self.assertEqual(data, b"")
+
+        run_concurrently(worker_func=worker, nthreads=NTHREADS - 1)
+        full_compressed = header + lzc.flush()
+        decompressed = lzma.decompress(full_compressed)
+        # The decompressed data should be INPUT repeated NTHREADS times
+        self.assertEqual(decompressed, INPUT * NTHREADS)
+
+    def test_decompressor(self):
+        chunk_size = 128
+        chunks = [bytes([ord("a") + i]) * chunk_size for i in range(NTHREADS)]
+        input_data = b"".join(chunks)
+        compressed = lzma.compress(input_data)
+
+        lzd = LZMADecompressor()
+        output = []
+
+        def worker():
+            data = lzd.decompress(compressed, chunk_size)
+            self.assertEqual(len(data), chunk_size)
+            output.append(data)
+
+        run_concurrently(worker_func=worker, nthreads=NTHREADS)
+        self.assertEqual(len(output), NTHREADS)
+        # Verify the expected chunks (order doesn't matter due to append race)
+        self.assertSetEqual(set(output), set(chunks))
+
+
+if __name__ == "__main__":
+    unittest.main()