diff --git a/tools/test/stress2/misc/ptrace12.sh b/tools/test/stress2/misc/ptrace12.sh
new file mode 100755
index 000000000000..b7381c4937e1
--- /dev/null
+++ b/tools/test/stress2/misc/ptrace12.sh
@@ -0,0 +1,82 @@
+#!/bin/sh
+
+#
+# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+#
+# Copyright (c) 2021 Peter Holm <pho@FreeBSD.org>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+
+[ `id -u ` -ne 0 ] && echo "Must be root!" && exit 1
+
+# D29955: ptrace(PT_COREDUMP) test scenario.
+
+# "panic: Assertion td->td_sleepqueue != NULL failed" seen with WiP kernel code.
+
+. ../default.cfg
+
+mount | grep $mntpoint | grep -q /dev/md && umount -f $mntpoint
+mdconfig -l | grep -q md$mdstart &&  mdconfig -d -u $mdstart
+mdconfig -a -t swap -s 2g -u $mdstart
+newfs $newfs_flags -n md$mdstart > /dev/null
+mount /dev/md$mdstart $mntpoint
+chmod 777 $mntpoint
+
+export runRUNTIME=10m
+export RUNDIR=$mntpoint/stressX
+set `df -ik $mntpoint | tail -1 | awk '{print $4,$7}'`
+export KBLOCKS=$(($1 / 2))
+export INODES=$(($2 / 2))
+
+su $testuser -c 'cd ..; ./run.sh marcus.cfg' &
+sleep 5
+while pgrep -q run; do
+	# exclude "swap" due to core file size
+	list=`ps -U$testuser | sed 1d | grep -vE "\.sh|run|defunct|swap" | \
+	    awk '{print $1}'`
+	[ -z "$list" ] && { pkill swap; continue; }
+	n=0
+	pids=
+	for p in $list; do
+		( gcore -k -c $mntpoint/core.$p $p 2>&1 | \
+		      grep -v 'No such process' ) &
+		pids="$pids $!"
+		n=$((n + 1))
+		[ $n -ge 2 ] && break
+	done
+	for p in "$pids"; do
+		wait $p
+	done
+	rm -f $mntpoint/core.*
+done
+while pkill -U$testuser; do sleep 2; done
+wait
+
+n=0
+while mount | grep $mntpoint | grep -q /dev/md; do
+	umount $mntpoint || sleep 1
+	[ $((n += 1)) -gt 300 ] && { echo FAIL; exit 1; }
+done
+checkfs /dev/md$mdstart; s=$?
+mdconfig -d -u $mdstart
+exit $s