On FreeBSD 11.0-CURRENT #0 r267672: Fri Jun 20 14:41:08 CEST 2014
email@example.com:/usr/src/sys/amd64/compile/PHO amd64 running the gbde.sh stress2 test repeatedly results in a deadlock. Details at http://people.freebsd.org/~pho/stress/log/gbde2.txt
It seems that the problem may be related to a slow g_bde_purge_sector() holding onto the g_bde_worklist which is the same one that IO requests wait on to queue new work. Thus any slowness in the worker thread will slow down and block the queueing of new work.
I am not seeing this problem any more.