gst_mini_object_unlock: assertion 'state >= SHARE_ONE' failed

Submitted by bill-auger

Description

Created attachment 315406
minimal pipeline exposing this bug

upon setting pipeline state to NULL at shutdown the following assertion is thrown repeatedly countless times:

GStreamer-CRITICAL **: gst_mini_object_unlock: assertion 'state >= SHARE_ONE' failed

this is accompanied by wild disk thrashing and in the larger project where this was discovered it quite often also renders the entire system unresponsive where the only remedy is to pull the plug

i have isolated this behavior to a bin containing a pngdec and imagefreeze and ghostpad src to another bin

a .cpp file with a minimal pipeline exposing this is attached - a thread dump and valgrind profile is available in this gist along with the same .cpp file
https://gist.github.com/bill-auger/b003a77c20cfbe8a704b

Attachment 315406, "minimal pipeline exposing this bug":
pngdec.cpp

Version: 1.6.1