[Python-checkins] cpython (3.4): Issue #22185: Fix an occasional RuntimeError in threading.Condition.wait()

[antoine.pitrou]

http://hg.python.org/cpython/rev/4cce39cfe46c
changeset:   92268:4cce39cfe46c
branch:      3.4
parent:      92262:a3452677a386
user:        Antoine Pitrou <solipsis at pitrou.net>
date:        Fri Aug 29 23:26:36 2014 +0200
summary:
  Issue #22185: Fix an occasional RuntimeError in threading.Condition.wait() caused by mutation of the waiters queue without holding the lock.

Patch by Doug Zongker.

files:
  Lib/threading.py |  11 ++++++-----
  Misc/ACKS        |   1 +
  Misc/NEWS        |   4 ++++
  3 files changed, 11 insertions(+), 5 deletions(-)


diff --git a/Lib/threading.py b/Lib/threading.py
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -284,6 +284,7 @@
         waiter.acquire()
         self._waiters.append(waiter)
         saved_state = self._release_save()
+        gotit = False
         try:    # restore state no matter what (e.g., KeyboardInterrupt)
             if timeout is None:
                 waiter.acquire()
@@ -293,14 +294,14 @@
                     gotit = waiter.acquire(True, timeout)
                 else:
                     gotit = waiter.acquire(False)
-                if not gotit:
-                    try:
-                        self._waiters.remove(waiter)
-                    except ValueError:
-                        pass
             return gotit
         finally:
             self._acquire_restore(saved_state)
+            if not gotit:
+                try:
+                    self._waiters.remove(waiter)
+                except ValueError:
+                    pass
 
     def wait_for(self, predicate, timeout=None):
         """Wait until a condition evaluates to True.
diff --git a/Misc/ACKS b/Misc/ACKS
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1500,4 +1500,5 @@
 Kai Zhu
 Tarek Ziadé
 Gennadiy Zlobin
+Doug Zongker
 Peter Åstrand
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -27,6 +27,10 @@
 Library
 -------
 
+- Issue #22185: Fix an occasional RuntimeError in threading.Condition.wait()
+  caused by mutation of the waiters queue without holding the lock.  Patch
+  by Doug Zongker.
+
 - Issue #22182: Use e.args to unpack exceptions correctly in
   distutils.file_util.move_file. Patch by Claudiu Popa.
 

-- 
Repository URL: http://hg.python.org/cpython