From d8862904641efabcded42a8db16f255f171e59e7 Mon Sep 17 00:00:00 2001
From: "Andrew M. Kuchling" <amk@amk.ca>
Date: Fri, 2 Apr 2010 17:48:23 +0000
Subject: #6647: document that catch_warnings is not thread-safe

---
 Doc/library/warnings.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Doc/library/warnings.rst b/Doc/library/warnings.rst
index e4343e8..91ab085 100644
--- a/Doc/library/warnings.rst
+++ b/Doc/library/warnings.rst
@@ -383,6 +383,14 @@ Available Context Managers
 
     .. note::
 
+        The :class:`catch_warnings` manager works by replacing and
+        then later restoring the module's
+        :func:`showwarning` function and internal list of filter
+        specifications.  This means the context manager is modifying
+        global state and therefore is not thread-safe.
+
+    .. note::
+
         In Python 3.0, the arguments to the constructor for
         :class:`catch_warnings` are keyword-only arguments.
 
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