apr-1.2.9, apr-util-1.2.8, gdbm-1.8.3, httpd-2.2.4, FreeBSD 6.1 [Tue Jul 24 19:12:32 2007] [error] [client ...] Could not LOCK /upload/index.html due to a failed precondition (e.g. other locks). [500, #0] [Tue Jul 24 19:12:32 2007] [error] [client ...] The locks could not be queried for verification against a possible "If:" header. [500, #0] [Tue Jul 24 19:12:32 2007] [error] [client ...] Item not found [500, #15] "Item not found"/#15 appears to be directly from gdbm. When I rebuilt apr-util to use sdbm, all was well.
CC myself on FreeBSD related bugs
I stumbled into this bug with httpd 2.4.6 as well and tracked it down. The problem is the APR DBM wrapper for GDBM, see bug #57900. BTW, it seems rather unsafe to use GDBM with mod_dav_fs in httpd 2.4.x with one of the threaded MPMs, as GDBM is not thread safe. Shouldn't mod_dav_fs explicitly request a known thread-safe DBM provider?
Marking as duplicate. Issues with thread-safety and DBM were fixed in r1914438 - more discussion at https://lists.apache.org/thread/81lrr7joy9r37b44mhlz6sc887lngmb2 *** This bug has been marked as a duplicate of bug 57900 ***