stress2: Added a regression test

tools/test/stress2/misc/killpg5.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# Test scenario from:
+# Bug 290843 - killpg deadlock against a stopped interrupted fork
+# By : Bryan Drewery <bdrewery@FreeBSD.org>
+
+# Seen:
+# 0 70877  3650  7   0  0 14856  3680 sigsusp  I+    0    0:00.00 sh -x ./killpg5.sh
+# 0 70881 70877 10   0  0 14856  3688 killpg r D+    0    0:00.07 sh -c trap "kill -9 %1; exit" INT; foo() { unset cmd; cmd=$(/sbin/sysctl -n vm.loadavg|/u
+
+sh -c 'trap "kill -9 %1; exit" INT; foo() { unset cmd; cmd=$(/sbin/sysctl -n vm.loadavg|/usr/bin/awk "{print \$2,\$3,\$4}"); case "${cmd:+set}" in set) ;; *) exit 99 ;; esac }; runner() { while foo; do :; done }; launch() { local -; set -m; PS4="child+ " runner & }; set -x; while :; do launch; sleep 0.1; kill -STOP %1; kill -TERM %1; kill -CONT %1; ret=0; wait; if [ $ret -eq 99 ]; then exit 99; fi; done;' > /dev/null 2>&1 &
+sleep 60
+kill -9 $!
+sleep .2
+killpgpid=`ps -lUroot | grep -v grep | grep ' killpg ' | awk '{print $2}'`
+[ -n "$killpgpid" ] && { ps -lp$killpgpid; exit 1; }	# The bug
+pgrep -f 'foo()' | xargs kill > /dev/null 2>&1		# Cleanup
+wait
+exit 0