bpo-45997: Fix asyncio.Semaphore re-acquiring order (GH-31910)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/Lib/test/test_asyncio/test_locks.py b/Lib/test/test_asyncio/test_locks.py
index d8b164a..920b3b5 100644
--- a/Lib/test/test_asyncio/test_locks.py
+++ b/Lib/test/test_asyncio/test_locks.py
@@ -917,6 +917,31 @@ class SemaphoreTests(unittest.IsolatedAsyncioTestCase):
         sem.release()
         self.assertFalse(sem.locked())
 
+    async def test_acquire_fifo_order(self):
+        sem = asyncio.Semaphore(1)
+        result = []
+
+        async def coro(tag):
+            await sem.acquire()
+            result.append(f'{tag}_1')
+            await asyncio.sleep(0.01)
+            sem.release()
+
+            await sem.acquire()
+            result.append(f'{tag}_2')
+            await asyncio.sleep(0.01)
+            sem.release()
+
+        async with asyncio.TaskGroup() as tg:
+            tg.create_task(coro('c1'))
+            tg.create_task(coro('c2'))
+            tg.create_task(coro('c3'))
+
+        self.assertEqual(
+            ['c1_1', 'c2_1', 'c3_1', 'c1_2', 'c2_2', 'c3_2'],
+            result
+        )
+
 
 if __name__ == '__main__':
     unittest.main()