udev: improve udev-cache robustness

* allow udev-cache to be disabled at runtime (using
   /etc/default/udev-cache);

 * make cache invalidated if kernel, bootparams or device list
   changes;

(From OE-Core rev: 22b72b23653736436f10d394de36201c32630d5d)

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/udev/udev.inc

@@ -25,6 +25,7 @@ SRC_URI = "${KERNELORG_MIRROR}/linux/utils/kernel/hotplug/udev-${PV}.tar.gz \
            file://network.sh \
            file://local.rules \
            file://udev-cache \
+           file://udev-cache.default \
            file://init"
 
 inherit autotools pkgconfig update-rc.d
@@ -58,7 +59,7 @@ FILES_libgudev = "${base_libdir}/libgudev*.so.* ${libdir}/libgudev*.so.*"
 FILES_libgudev-dbg = "${base_libdir}/.debug/libgudev*.so.* ${libdir}/.debug/libgudev*.so.*"
 FILES_libgudev-dev = "${includedir}/gudev* ${libdir}/libgudev*.so ${libdir}/libgudev*.la \
                      ${libdir}/libgudev*.a ${libdir}/pkgconfig/gudev*.pc"
-FILES_udev-cache = "${sysconfdir}/init.d/udev-cache"
+FILES_udev-cache = "${sysconfdir}/init.d/udev-cache ${sysconfdir}/default/udev-cache"
 
 FILES_udev-acl = "${base_libdir}/udev/udev-acl ${base_libdir}/udev/rules.d/70-acl.rules"
 
@@ -72,6 +73,11 @@ do_install_append () {
 	install -m 0755 ${WORKDIR}/init ${D}${sysconfdir}/init.d/udev
 	install -m 0755 ${WORKDIR}/udev-cache ${D}${sysconfdir}/init.d/udev-cache
 
+	install -d ${D}${sysconfdir}/default
+	install -m 0755 ${WORKDIR}/udev-cache.default ${D}${sysconfdir}/default/udev-cache
+
+	touch ${D}${sysconfdir}/udev/cache.data
+
 	install -d ${D}${sysconfdir}/udev/rules.d/
 
 	install -m 0644 ${WORKDIR}/local.rules         ${D}${sysconfdir}/udev/rules.d/local.rules

meta/recipes-core/udev/udev/init

@@ -14,8 +14,19 @@ export TZ=/etc/localtime
 [ -d /sys/class ] || exit 1
 [ -r /proc/mounts ] || exit 1
 [ -x /sbin/udevd ] || exit 1
+[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
 [ -f /etc/udev/udev.conf ] && . /etc/udev/udev.conf
 
+readfile () {
+   filename=$1
+   READDATA=""
+   if [ -r $filename ]; then
+       while read line; do
+           READDATA="$READDATA$line"
+       done < $filename
+   fi
+}
+
 kill_udevd() {
 	if [ -x /sbin/pidof ]; then
 		pid=`/sbin/pidof -x udevd`
@@ -34,10 +45,26 @@ LANG=C awk '$2 == "/dev" && ($3 == "tmpfs" || $3 == "devtmpfs") { exit 1 }' /pro
 [ -e /dev/pts ] || mkdir -m 0755 /dev/pts
 [ -e /dev/shm ] || mkdir -m 1777 /dev/shm
 
+# cache handling
+if [ "$DEVCACHE" != "" ]; then
+	readfile /proc/version
+	VERSION="$READDATA"
+	readfile /proc/cmdline
+	CMDLINE="$READDATA"
+	readfile /proc/devices
+	DEVICES="$READDATA"
+	readfile /proc/atags
+	ATAGS="$READDATA"
 
-if [ -e /etc/dev.tar ]; then
-	(cd /; tar xf /etc/dev.tar 2>&1 | grep -v 'time stamp' || true)
-	not_first_boot=1
+	if [ -e $DEVCACHE ]; then
+		readfile /etc/udev/cache.data
+		if [ "$READDATA" = "$VERSION$CMDLINE$DEVICES$ATAGS" ]; then
+			(cd /; tar xf $DEVCACHE > /dev/null 2>&1)
+			not_first_boot=1
+		fi
+
+		echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
+	fi
 fi
 
 # make_extra_nodes

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

@@ -9,12 +9,20 @@
 # Short-Description: cache /dev to speedup the udev next boot
 ### END INIT INFO
 
-[ -d /sys/class ] || exit 1
+export TZ=/etc/localtime
+
 [ -r /proc/mounts ] || exit 1
 [ -x /sbin/udevd ] || exit 1
+[ -d /sys/class ] || exit 1
 
-if [ ! -e /etc/dev.tar ]; then
-	(cd /; tar cf /etc/dev.tar dev)
+[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
+
+if [ "$DEVCACHE" != "" ]; then
+	echo "Populating dev cache"
+	(cd /; tar cf "$DEVCACHE" dev)
+	mv /dev/shm/udev.cache /etc/udev/cache.data
+else
+	rm -f /dev/shm/udev.cache
 fi
 
 exit 0

meta/recipes-core/udev/udev/udev-cache.default

@@ -0,0 +1,4 @@
+# Default for /etc/init.d/udev
+
+# Comment this out to disable device cache
+DEVCACHE="/etc/dev.tar"

meta/recipes-core/udev/udev_164.bb

@@ -1,6 +1,6 @@
 include udev.inc
 
-PR = "r9"
+PR = "r10"
 
 SRC_URI += "file://udev-166-v4l1-1.patch"