utils.py: remove 'is_single_threaded' method, we use it only in tests

This moves it to tests with a simplified usage, since we don't use it
anywhere else

2 files changed, 23 insertions, 40 deletions

diff --git a/src/buildstream/testing/_fixtures.py b/src/buildstream/testing/_fixtures.py
index 520f68587..095a5f6f1 100644
--- a/src/buildstream/testing/_fixtures.py
+++ b/src/buildstream/testing/_fixtures.py
@@ -16,26 +16,44 @@
 
 # pylint: disable=redefined-outer-name
 
+import time
+
 import psutil
 import pytest
 
-from buildstream import node, utils, DownloadableFileSource
+from buildstream import node, DownloadableFileSource
+
+
+# Number of seconds to wait for background threads to exit.
+_AWAIT_THREADS_TIMEOUT_SECONDS = 5
+
+
+def has_no_unexpected_background_threads(expected_num_threads):
+    # Use psutil as threading.active_count() doesn't include gRPC threads.
+    process = psutil.Process()
+
+    wait = 0.1
+    for _ in range(0, int(_AWAIT_THREADS_TIMEOUT_SECONDS / wait)):
+        if process.num_threads() == expected_num_threads:
+            return True
+        time.sleep(wait)
+
+    return False
 
 
 @pytest.fixture(autouse=True, scope="session")
 def default_thread_number():
     # xdist/execnet has its own helper thread.
-    # Ignore that for `utils._is_single_threaded` checks.
-    utils._INITIAL_NUM_THREADS_IN_MAIN_PROCESS = psutil.Process().num_threads()
+    return psutil.Process().num_threads()
 
 
 # Catch tests that don't shut down background threads, which could then lead
 # to other tests hanging when BuildStream uses fork().
 @pytest.fixture(autouse=True)
 def thread_check(default_thread_number):
-    assert utils._is_single_threaded()
+    assert has_no_unexpected_background_threads(default_thread_number)
     yield
-    assert utils._is_single_threaded()
+    assert has_no_unexpected_background_threads(default_thread_number)
 
 
 # Reset global state in node.pyx to improve test isolation
diff --git a/src/buildstream/utils.py b/src/buildstream/utils.py
index 8e6a51273..04bbf261c 100644
--- a/src/buildstream/utils.py
+++ b/src/buildstream/utils.py
@@ -35,7 +35,6 @@ import subprocess
 from subprocess import TimeoutExpired
 import tempfile
 import threading
-import time
 import datetime
 import itertools
 from contextlib import contextmanager
@@ -62,16 +61,6 @@ BST_ARBITRARY_TIMESTAMP = calendar.timegm((2011, 11, 11, 11, 11, 11))
 _ALIAS_SEPARATOR = ":"
 _URI_SCHEMES = ["http", "https", "ftp", "file", "git", "sftp", "ssh"]
 
-# Main process pid
-_MAIN_PID = os.getpid()
-
-# The number of threads in the main process at startup.
-# This is 1 except for certain test environments (xdist/execnet).
-_INITIAL_NUM_THREADS_IN_MAIN_PROCESS = 1
-
-# Number of seconds to wait for background threads to exit.
-_AWAIT_THREADS_TIMEOUT_SECONDS = 5
-
 # The process's file mode creation mask.
 # Impossible to retrieve without temporarily changing it on POSIX.
 _UMASK = os.umask(0o777)
@@ -1600,30 +1589,6 @@ def _get_compression(tar):
         return ""
 
 
-# _is_single_threaded()
-#
-# Return whether the current Process is single-threaded. Don't count threads
-# in the main process that were created by a test environment (xdist/execnet)
-# before BuildStream was executed.
-#
-def _is_single_threaded():
-    # Use psutil as threading.active_count() doesn't include gRPC threads.
-    process = psutil.Process()
-
-    if process.pid == _MAIN_PID:
-        expected_num_threads = _INITIAL_NUM_THREADS_IN_MAIN_PROCESS
-    else:
-        expected_num_threads = 1
-
-    # gRPC threads are not joined when shut down. Wait for them to exit.
-    wait = 0.1
-    for _ in range(0, int(_AWAIT_THREADS_TIMEOUT_SECONDS / wait)):
-        if process.num_threads() == expected_num_threads:
-            return True
-        time.sleep(wait)
-    return False
-
-
 # _parse_version():
 #
 # Args: