3 files changed, 38 insertions, 4 deletions

diff --git a/Mailman/Cgi/admin.py b/Mailman/Cgi/admin.py
index 1e4b710b7..95d5558af 100644
--- a/Mailman/Cgi/admin.py
+++ b/Mailman/Cgi/admin.py
@@ -24,6 +24,7 @@ import cgi
 import types
 import sha
 import urllib
+import signal
 from string import lowercase, digits
 
 from mimelib.address import unquote
@@ -121,7 +122,7 @@ def main():
     # The html page document
     doc = Document()
     doc.set_language(mlist.preferred_language)
-    # Now we're ready to do normal form processing.  For this, though we must
+    # Now we're ready to do normal form processing.  For this though, we must
     # lock the mailing list, and everything from here on out must be wrapped
     # in a try/except.
     #
@@ -130,8 +131,23 @@ def main():
     # or stale lock on the list.  Maybe we should have a configurable timeout
     # setting after which we'll just inform the user that the operation
     # couldn't be performed?
+    #
+    # Set things up so that we can clean up the list lock even if the user
+    # hits the browser's stop button.  Note that Apache under mod_cgi
+    # apparently can catch the SIGPIPE that results, and calls SIGTERM on the
+    # CGI process.  Python doesn't install a signal handler for SIGTERM, so
+    # that would cause us to summarily exit, leaving list locks laying around
+    # (and this behavior has been confirmed).  We can't just ignore SIGTERM
+    # because three seconds later Apache will SIGKILL us, giving us no chance
+    # to exit cleanly.  By installing this signal handler, we can catch the
+    # SIGTERM and do the right thing.  This may not work under other web
+    # servers, or even other Apache/cgi modules (mod_python, etc.).
+    def sigterm_handler(signum, frame, mlist=mlist):
+        mlist.Unlock()
+
     mlist.Lock()
     try:
+        signal.signal(signal.SIGTERM, sigterm_handler)
         if cgidata.keys():
             # There are options to change
             change_options(mlist, category, cgidata, doc)
@@ -161,8 +177,12 @@ def main():
         # Glom up the results page and print it out
         show_results(mlist, doc, category, category_suffix, cgidata)
         print doc.Format(bgcolor='#ffffff')
-    finally:
         mlist.Save()
+    finally:
+        # Now be sure to unlock the list.  It's okay if we get a signal here
+        # because essentially, the signal handler will do the same thing.  And
+        # unlocking is conditional, so it's not an error if we unlock while
+        # we're already unlocked.
         mlist.Unlock()
 
 
diff --git a/Mailman/Cgi/admindb.py b/Mailman/Cgi/admindb.py
index 65b33e975..cc061be26 100644
--- a/Mailman/Cgi/admindb.py
+++ b/Mailman/Cgi/admindb.py
@@ -20,6 +20,7 @@ import os
 import types
 import cgi
 import errno
+import signal
 
 from mimelib.Parser import Parser
 from mimelib.MsgReader import MsgReader
@@ -78,8 +79,14 @@ def main():
     # should not need to be locked just to read the request database.  However
     # the request database asserts that the list is locked in order to load
     # it and it's not worth complicating that logic.
+    #
+    # Also, see the comment in admin.py about the need for the signal handler.
+    def sigterm_handler(signum, frame, mlist=mlist):
+        mlist.Unlock()
+
     mlist.Lock()
     try:
+        signal.signal(signal.SIGTERM, sigterm_handler)
         realname = mlist.real_name
         if not cgidata.keys():
             # If this is not a form submission (i.e. there are no keys in the
@@ -91,8 +98,8 @@ def main():
             process_form(mlist, doc, cgidata)
         # Now print the results and we're done
         show_requests(mlist, doc)
-    finally:
         mlist.Save()
+    finally:
         mlist.Unlock()
 
     print doc.Format(bgcolor='#ffffff')
diff --git a/Mailman/Cgi/confirm.py b/Mailman/Cgi/confirm.py
index 2fabebff8..2fee4d930 100644
--- a/Mailman/Cgi/confirm.py
+++ b/Mailman/Cgi/confirm.py
@@ -16,6 +16,8 @@
 
 """Confirm a pending action via URL."""
 
+import signal
+
 from Mailman import mm_cfg
 from Mailman import Errors
 from Mailman import i18n
@@ -55,9 +57,14 @@ def main():
     i18n.set_language(mlist.preferred_language)
     doc.set_language(mlist.preferred_language)
 
+    # See the comment in admin.py about the need for the signal handler.
+    def sigterm_handler(signum, frame, mlist=mlist):
+        mlist.Unlock()
+
     # Now dig out the cookie
     mlist.Lock()
     try:
+        signal.signal(signal.SIGTERM, sigterm_handler)
         try:
             cookie = parts[1]
             data = mlist.ProcessConfirmation(cookie)
@@ -70,8 +77,8 @@ def main():
             please try to re-submit your subscription.'''))
         doc.AddItem(mlist.GetMailmanFooter())
         print doc.Format(bgcolor='#ffffff')
-    finally:
         mlist.Save()
+    finally:
         mlist.Unlock()