Skiplist errors on Cyrus 2.3.12

[Bron Gondwana]

On Fri, Jul 11, 2008 at 11:37:52AM +0200, Reinhard Zierke wrote:
> Jul 11 10:32:41 mailhost.informatik.uni-hamburg.de cyradm[13944]: [ID 637875 local6.error] Fatal error: Internal error: assertion failed: cyrusdb_skiplist.c: 622: db->lock_status == UNLOCKED
> Jul 11 10:32:41 mailhost.informatik.uni-hamburg.de cyradm[13944]: [ID 558109 local6.error] skiplist: closed while still locked

We think we've figured this one out now :)  Finally.  John Capo came up
with a basic patch that fixed it, and I've done a slightly more
ambitious refactor.  Rudy has tested my patch, and we're running it at
FastMail as well.

I've rebuild our webpage with the new patch included.  NOTE: this patch
obsoletes the old readlocktracking patch, and conflicts with it.  This
way is much cleaner.

Bron.

http://cyrus.brong.fastmail.fm/patches/cyrus-skiplist-locking-rework-2.3.12.diff