Fix class BoundedAttributes to have RLock rather than Lock

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fix class BoundedAttributes to have RLock rather than Lock
+  ([#3859](https://github.com/open-telemetry/opentelemetry-python/pull/3859))
 - Remove thread lock by loading RuntimeContext explicitly.
   ([#3763](https://github.com/open-telemetry/opentelemetry-python/pull/3763))
 - Update proto version to v1.2.0

opentelemetry-api/src/opentelemetry/attributes/__init__.py

@@ -150,7 +150,7 @@ def __init__(
         self.max_value_len = max_value_len
         # OrderedDict is not used until the maxlen is reached for efficiency.
         self._dict = {}  # type: dict | OrderedDict
-        self._lock = threading.Lock()  # type: threading.Lock
+        self._lock = threading.RLock()  # type: threading.RLock
         if attributes:
             for key, value in attributes.items():
                 self[key] = value

opentelemetry-api/tests/attributes/test_attributes.py

@@ -180,3 +180,17 @@ def test_immutable(self):
         bdict = BoundedAttributes()
         with self.assertRaises(TypeError):
             bdict["should-not-work"] = "dict immutable"
+
+    def test_locking(self):
+        """Supporting test case for a commit titled: Fix class BoundedAttributes to have RLock rather than Lock. See #3858.
+        The change was introduced because __iter__ of the class BoundedAttributes holds lock, and we observed some deadlock symptoms
+        in the codebase. This test case is to verify that the fix works as expected.
+        """
+        bdict = BoundedAttributes(immutable=False)
+
+        with bdict._lock:
+            for num in range(100):
+                bdict[str(num)] = num
+
+        for num in range(100):
+            self.assertEqual(bdict[str(num)], num)