Fix Arial.ttf threaded multi-download bug (#3725)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/utils/__init__.py

@@ -252,6 +252,36 @@ if WINDOWS:  # emoji-safe logging
     LOGGER.addFilter(EmojiFilter())
 
 
+class ThreadingLocked:
+    """
+    A decorator class for ensuring thread-safe execution of a function or method.
+    This class can be used as a decorator to make sure that if the decorated function
+    is called from multiple threads, only one thread at a time will be able to execute the function.
+
+    Attributes:
+        lock (threading.Lock): A lock object used to manage access to the decorated function.
+
+    Usage:
+        @ThreadingLocked()
+        def my_function():
+            # Your code here
+            pass
+    """
+
+    def __init__(self):
+        self.lock = threading.Lock()
+
+    def __call__(self, f):
+        from functools import wraps
+
+        @wraps(f)
+        def decorated(*args, **kwargs):
+            with self.lock:
+                return f(*args, **kwargs)
+
+        return decorated
+
+
 def yaml_save(file='data.yaml', data=None):
     """
     Save YAML data to a file.

ultralytics/yolo/utils/checks.py

@@ -20,9 +20,9 @@ import requests
 import torch
 from matplotlib import font_manager
 
-from ultralytics.yolo.utils import (AUTOINSTALL, LOGGER, ONLINE, ROOT, USER_CONFIG_DIR, TryExcept, clean_url, colorstr,
+from ultralytics.yolo.utils import (AUTOINSTALL, LOGGER, ONLINE, ROOT, USER_CONFIG_DIR, ThreadingLocked, TryExcept,
-                                    downloads, emojis, is_colab, is_docker, is_jupyter, is_kaggle, is_online,
+                                    clean_url, colorstr, downloads, emojis, is_colab, is_docker, is_jupyter, is_kaggle,
-                                    is_pip_package, url2file)
+                                    is_online, is_pip_package, url2file)
 
 
 def is_ascii(s) -> bool:
@@ -155,6 +155,7 @@ def check_pip_update_available():
     return False
 
 
+@ThreadingLocked()
 def check_font(font='Arial.ttf'):
     """
     Find font locally or download to user's configuration directory if it does not already exist.