rc.subr: Fix premature return from wait_for_pids

Use pwait's new -r option to wait until the target processes have not
only terminated, but also been reaped.

PR:		293183
MFC after:	1 week
Sponsored by:	Klara, Inc.
Sponsored by:	NetApp, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D58391

UPDATING

@@ -27,6 +27,18 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 16.x IS SLOW:
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20260722:
+	The wait_for_pids() function in rc.subr, used by rc scripts
+	when stopping or restarting a service, has been modified to
+	use pwait(1)'s new -r option, which requires kernel support.
+	When upgrading across this change, you should install a new
+	kernel first, then reboot, then install a new world, run
+	etcupdate, and reboot again.  Otherwise, you may find that
+	rc.subr is unable to stop services because the running kernel
+	does not provide the support that the updated pwait(1) needs.
+	Alternatively, if you deem it safe, you may use fastboot(8) to
+	reboot without shutting down services first.
+
 20260620:
 	On powerpc64le, long double is now IEEE 754 binary128 (quad
 	precision, 113-bit mantissa) instead of 64-bit double.  This is an

libexec/rc/rc.subr

@@ -803,7 +803,7 @@ sort_lite()
 #
 wait_for_pids()
 {
-	local _list _prefix _j
+	local _list= _prefix= _j=
 
 	for _j in "$@"; do
 		if kill -0 $_j 2>/dev/null; then
@@ -814,7 +814,7 @@ wait_for_pids()
 	while [ -n "$_list" ]; do
 		echo -n ${_prefix:-"Waiting for PIDS: "}$_list
 		_prefix=", "
-		_list=$(pwait -op $_list 2>/dev/null)
+		_list=$(pwait -opr $_list 2>/dev/null)
 	done
 	if [ -n "$_prefix" ]; then
 		echo "."

libexec/rc/tests/rc_subr_test.sh

@@ -123,20 +123,12 @@ wait_for_pids_progress_head()
 }
 wait_for_pids_progress_body()
 {
-	cat >>script <<'EOF'
-. /etc/rc.subr
-sleep 15 &
-a=$!
-sleep 10 &
-b=$!
-sleep 5 &
-c=$!
-wait_for_pids $a $b $c
-EOF
-	re="^Waiting for PIDS: [0-9]+ [0-9]+ [0-9]+"
-	re="${re}, [0-9]+ [0-9]+"
-	re="${re}, [0-9]+\.$"
-	atf_check -s exit:0 -o match:"${re}" /bin/sh script
+	a=$(sleep 4 >/dev/null & echo $!)
+	b=$(sleep 3 >/dev/null & echo $!)
+	c=$(sleep 2 >/dev/null & echo $!)
+	atf_check \
+	    -o inline:"Waiting for PIDS: $a $b $c, $a $b, $a.\n" \
+	    /bin/sh -c ". /etc/rc.subr; wait_for_pids $a $b $c"
 }
 
 atf_init_test_cases()