udev-cache: fix to use udev-cache correctly

Previouly, the udev-cache has no real effect even if it's installed
into the system. The key problem here is that at first boot, the
/etc/dev.tar is not present, thus resulting /dev/shm/udev.cache not
created on first boot even if udev-cache is enabled.

This patch fixes this problem. The /dev/shm/udev.cache will be created
if necessary, that is, on first boot or when some part of the system is
changed. In the latter case, the udev cache may not be valid.

[YOCTO #4738]

(From OE-Core rev: 84e0ec2e677fb0236a38478372cdd75797cf5a2e)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/systemd/systemd/init

@@ -59,8 +59,12 @@ case "$1" in
                     if [ "$READDATA" = "$VERSION$CMDLINE$DEVICES$ATAGS" ]; then
                             (cd /; tar xf $DEVCACHE > /dev/null 2>&1)
                             not_first_boot=1
+                            [ "$VERBOSE" != "no" ] && echo "udev: using cache file $DEVCACHE"
+                            [ -e /dev/shm/udev.cache ] && rm -f /dev/shm/udev.cache
+                    else
+                            echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
                     fi
-
+            else
                     echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
             fi
     fi

meta/recipes-core/udev/udev/init

@@ -68,8 +68,12 @@ case "$1" in
                     if [ "$READDATA" = "$VERSION$CMDLINE$DEVICES$ATAGS" ]; then
                             (cd /; tar xf $DEVCACHE > /dev/null 2>&1)
                             not_first_boot=1
+                            [ "$VERBOSE" != "no" ] && echo "udev: using cache file $DEVCACHE"
+                            [ -e /dev/shm/udev.cache ] && rm -f /dev/shm/udev.cache
+                    else
+                            echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
                     fi
-
+            else
                     echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
             fi
     fi

meta/recipes-core/udev/udev/udev-cache

@@ -17,12 +17,10 @@ export TZ=/etc/localtime
 
 [ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
 
-if [ "$DEVCACHE" != "" ]; then
+if [ "$DEVCACHE" != "" -a -e /dev/shm/udev.cache ]; then
 	echo "Populating dev cache"
 	(cd /; tar cf "$DEVCACHE" dev)
 	mv /dev/shm/udev.cache /etc/udev/cache.data
-else
-	rm -f /dev/shm/udev.cache
 fi
 
 exit 0