# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1446831273 -3600
# Node ID cad23243f170b78e48a74b8df43a9542293efcca
# Parent  e81fe95cfbd68e400651ab81011327d6f280b1e0
Adopted unique "old" lock directory names to prevent race conditions causing
exceptions and locks being left in place.

diff -r e81fe95cfbd6 -r cad23243f170 imiptools/filesys.py
--- a/imiptools/filesys.py	Fri Nov 06 17:17:22 2015 +0100
+++ b/imiptools/filesys.py	Fri Nov 06 18:34:33 2015 +0100
@@ -172,10 +172,16 @@
         parts = parts and list(parts) or []
         target = parts[:]
 
-        # Move the directory.
+        # Move the directory to a unique name. This prevents unlikely but
+        # possible conflicts as a slow unlocking process is caught up by a
+        # following, faster locking-then-unlocking process which would then
+        # try and rename the active lock directory to a common old lock
+        # directory name, causing a "directory not empty" exception and the
+        # continued existence of the lock.
 
         parts.append(self.lock_name)
-        target.append(self.old_lock_name)
+        old_lock_name = "%s.%d" % (self.old_lock_name, getpid())
+        target.append(old_lock_name)
         rename(self.get_object_in_store(*parts), self.get_object_in_store(*target))
 
         # Then remove the moved directory and its contents.