main(): Before we write to the aliases.db file, we must drop an

exclusive advisory lock on it, so Postfix doesn't try to read the file
while we're updating it.  For a discussion of why we have to do this
so cruftily, see Mailman/MTA/Postfix.py

1 files changed, 9 insertions, 1 deletions

diff --git a/bin/genaliases b/bin/genaliases
index 951c3eabc..b71a74d1b 100644
--- a/bin/genaliases
+++ b/bin/genaliases
@@ -31,6 +31,7 @@ Options:
 import sys
 import getopt
 import dbhash
+import fcntl
 
 import paths                                      # path hacking
 from Mailman import Utils
@@ -66,9 +67,13 @@ def main():
     # we're doing it.
     lock = Postfix.makelock()
     lock.lock()
+    lockfp = None
     try:
         # Overwrite the current file contents, since we're going to be adding
-        # all new entries.
+        # all new entries.  See the discussion in Mailman/MTA/Postfix.py for
+        # why we do the locking this way.
+        lockfp = open(Postfix.DBFILE)
+        fcntl.flock(lockfp.fileno(), fcntl.LOCK_EX)
         db = dbhash.open(Postfix.DBFILE, 'n')
         fp = open(Postfix.TEXTFILE, 'w')
         for listname in Utils.list_names():
@@ -77,6 +82,9 @@ def main():
         db.sync()
         fp.close()
     finally:
+        if lockfp:
+            fcntl.flock(lockfp.fileno(), fcntl.LOCK_UN)
+            lockfp.close()
         lock.unlock(unconditionally=1)