4.76. I can't access one of my lists via the web interface. One of my lists is not sending mail. List locked.
Problems that affect only one list in an installation can be caused by stale locks for the list.
A list lock is implemented as a pair of files in mailman's locks/ directory. One file is named '<listname>.lock' and the other is named '<listname>.lock.<hostname>.<pid>.<seq>' where
<listname> is the name of the list
<hostname> is the name of the host that set the lock
<pid> is the process id of the process on <hostname> that set the lock
<seq> is a sequence number
The contents of both files (actually they are the same file with two names - hard linked) is
There may be additional files named '<listname>.lock.<hostname>.<pid>.<seq>' for the same listname. These represent lock requests waiting for the lock to be relinquished.
Sometimes due to a crash of some sort, a lock will be left in place after the process that set it is gone. This is a stale lock. One can often identify a stale lock by its age. Also, if <pid> no longer exists on <hostname>, the lock is definitely stale.
Stale locks can safely be simply removed. If there are other processes waiting on the stale lock, removing the '<listname>.lock' file will allow the other processes to acquire and relinquish the lock normally.
Note that pre-2.1.7 Mailman could stop sending to a single list because of a problem with a message in the lists/<listname>/digest.mbox file. This will not affect the web interface for the list, but if this is why the list is not sending, there will be a 'shunting' message and a traceback of an exception involving Mailman/Handlers/ToDigest.py in Mailman's 'error' log for each list post. See the post at http://mail.python.org/pipermail/mailman-users/2007-December/059426.html and other posts referenced by it for more information, but note that this post only discusses one specific error. There are many other possible message defects that can cause a different exception with the same end result.
Converted from the Mailman FAQ Wizard
This is one of many Frequently Asked Questions.