shutdown: sleep a little, if a process was killed

If a process (maybe plymouth) was still pinning /oldroot, then shutdown
would
- kill -9 $pid
- umount_a
- umount_a
in a very short timeframe. A small sleep hopefully lets the scheduler free
up /oldroot in the mean time.

modules.d/99base/dracut-lib.sh

@@ -118,6 +118,7 @@ str_replace() {
 killall_proc_mountpoint() {
     local _pid
     local _t
+    local _killed=0
     for _pid in /proc/*; do
         _pid=${_pid##/proc/}
         case $_pid in
@@ -125,8 +126,12 @@ killall_proc_mountpoint() {
         esac
         [ -e "/proc/$_pid/exe" ] || continue
         [ -e "/proc/$_pid/root" ] || continue
-        strstr "$(ls -l -- "/proc/$_pid" "/proc/$_pid/fd" 2>/dev/null)" "$1" && kill -9 "$_pid"
+        if strstr "$(ls -l -- "/proc/$_pid" "/proc/$_pid/fd" 2>/dev/null)" "$1" ; then
+            kill -9 "$_pid"
+            _killed=1
+        fi
     done
+    return $_killed
 }
 
 getcmdline() {

modules.d/99shutdown/module-setup.sh

@@ -14,7 +14,7 @@ depends() {
 # called by dracut
 install() {
     local _d
-    inst_multiple umount poweroff reboot halt losetup stat
+    inst_multiple umount poweroff reboot halt losetup stat sleep
     inst_multiple -o kexec
     inst "$moddir/shutdown.sh" "$prefix/shutdown"
     [ -e "${initdir}/lib" ] || mkdir -m 0755 -p ${initdir}/lib

modules.d/99shutdown/shutdown.sh

@@ -38,7 +38,7 @@ source_hook pre-shutdown
 
 warn "Killing all remaining processes"
 
-killall_proc_mountpoint /oldroot
+killall_proc_mountpoint /oldroot || sleep 0.2
 
 umount_a() {
     local _did_umount="n"