Re: Logical decoding (contrib/test_decoding) walsender broken in 9.5 master?

I started bisecting from e6df2e1 (stamp 9.4beta1, good) to 095d401 (bad).
The problem revision appears to be 9402869:

commit 9402869
Author: Heikki Linnakangas <heikki(dot)linnakangas(at)iki(dot)fi>
Date: Sat Jan 17 01:14:32 2015 +0200

Advance backend's advertised xmin more aggressively.

which is somewhat logical given the crash location and symptoms.

Bisection procedure used:

For each step:

./configure --enable-debug --enable-cassert --prefix=/home/craig/pg/95
CFLAGS="-Og -ggdb -fno-omit-frame-pointer" && make clean install && make -C
contrib/test_decoding/ clean install && rm -rf ~/tmp/slottest95 &&
PATH=$HOME/pg/95/bin:$PATH initdb -D ~/tmp/slottest95 && cp
~/tmp/{postgresql.conf,pg_hba.conf} ~/tmp/slottest95 &&
PATH=$HOME/pg/95/bin:$PATH PGPORT=5123 postgres -D ~/tmp/slottest95/

then manually:

psql -p 5123 -c 'SELECT pg_create_logical_replication_slot('test',
'test_decoding');'

PGPORT=5123 PATH=$HOME/pg/95/bin:$PATH pg_recvlogical -d postgres -S test
--start -f -

psql -p 5123 -c 'CREATE TABLE x AS SELECT xx FROM generate_series(1,10000)
xx;'

I have to go out now; I'll follow up further but wanted to update promptly.