testsuite: use concurrent.futures.ThreadPoolExecutor in the driver

The testsuite driver used to create one thread per test case, and
explicitly use semaphore and locks for rate limiting and
synchronization. This is a bad practice in any language, and
occasionally may result in livelock conditions (e.g. #22889). This
patch uses concurrent.futures.ThreadPoolExecutor for scheduling test
case runs, which is simpler and more robust.

1 files changed, 0 insertions, 20 deletions

diff --git a/testsuite/driver/testutil.py b/testsuite/driver/testutil.py
index e7b6bf2948..f2c63c5a2d 100644
--- a/testsuite/driver/testutil.py
+++ b/testsuite/driver/testutil.py
@@ -5,8 +5,6 @@ import tempfile
 from pathlib import Path, PurePath
 from term_color import Color, colored
 
-import threading
-
 from my_typing import *
 
 
@@ -125,24 +123,6 @@ else:
         else:
             os.symlink(str(src), str(dst))
 
-class Watcher(object):
-    def __init__(self, count: int) -> None:
-        self.pool = count
-        self.evt = threading.Event()
-        self.sync_lock = threading.Lock()
-        if count <= 0:
-            self.evt.set()
-
-    def wait(self):
-        self.evt.wait()
-
-    def notify(self):
-        self.sync_lock.acquire()
-        self.pool -= 1
-        if self.pool <= 0:
-            self.evt.set()
-        self.sync_lock.release()
-
 def memoize(f):
     """
     A decorator to memoize a nullary function.