Patchwork [6/9] udev: improve udev-cache robustness

diff --git a/meta/recipes-core/udev/udev.inc b/meta/recipes-core/udev/udev.inc
index eac7903..7b6ed64 100644
--- a/meta/recipes-core/udev/udev.inc
+++ b/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
@@ -56,7 +57,7 @@  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"
 
@@ -68,6 +69,14 @@  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/saved.uname
+	touch ${D}${sysconfdir}/udev/saved.cmdline
+	touch ${D}${sysconfdir}/udev/saved.devices
+	touch ${D}${sysconfdir}/udev/saved.atags
+
 	install -d ${D}${sysconfdir}/udev/rules.d/
 
 	install -m 0644 ${WORKDIR}/local.rules         ${D}${sysconfdir}/udev/rules.d/local.rules
diff --git a/meta/recipes-core/udev/udev/init b/meta/recipes-core/udev/udev/init
index 0b25b07..a2b6f53 100644
--- a/meta/recipes-core/udev/udev/init
+++ b/meta/recipes-core/udev/udev/init
@@ -14,6 +14,7 @@  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
 
 kill_udevd() {
@@ -34,9 +35,20 @@  LANG=C awk '$2 == "/dev" && $3 == "tmpfs" || $3 == "devtmpfs") { exit 1 }' /proc
 	mkdir -m 1777 /dev/shm
 }
 
-if [ -e /etc/dev.tar ]; then
-	(cd /; tar xf /etc/dev.tar 2>&1 | grep -v 'time stamp' || true)
-	not_first_boot=1
+if [ "$DEVCACHE" != "" ]; then
+	# Invalidate udev cache if the kernel or its bootargs/cmdline have changed
+	[ -x /bin/uname ] && /bin/uname -mrspv > /tmp/uname || touch /tmp/uname
+	[ -r /proc/cmdline ] && cat /proc/cmdline > /tmp/cmdline || touch /tmp/cmdline
+	[ -r /proc/devices ] && cat /proc/devices > /tmp/devices || touch /tmp/devices
+	[ -r /proc/atags ] && cat /proc/atags > /tmp/atags || touch /tmp/atags
+	if [ -e $DEVCACHE ] && \
+		cmp -s /tmp/uname /etc/udev/saved.uname && \
+		cmp -s /tmp/cmdline /etc/udev/saved.cmdline && \
+		cmp -s /tmp/devices /etc/udev/saved.devices && \
+		cmp -s /tmp/atags /etc/udev/saved.atags; then
+		(cd /; tar xf $DEVCACHE > /dev/null 2>&1)
+		not_first_boot=1
+	fi
 fi
 
 # make_extra_nodes
diff --git a/meta/recipes-core/udev/udev/udev-cache b/meta/recipes-core/udev/udev/udev-cache
index 77bbda6..797cb82 100644
--- a/meta/recipes-core/udev/udev/udev-cache
+++ b/meta/recipes-core/udev/udev/udev-cache
@@ -9,12 +9,25 @@ 
 # Short-Description: cache /dev to speedup the udev next boot
 ### END INIT INFO
 
-[ -d /sys/class ] || exit 1
-[ -r /proc/mounts ] || exit 1
-[ -x /sbin/udevd ] || exit 1
+export TZ=/etc/localtime
 
-if [ ! -e /etc/dev.tar ]; then
-	(cd /; tar cf /etc/dev.tar dev)
+[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
+
+echo "Caching udev devnodes"
+
+if [ "$DEVCACHE" != "" ]; then
+	echo -n "Populating dev cache"
+	(cd /; tar cf $DEVCACHE dev)
+	mv /tmp/uname /etc/udev/saved.uname
+	mv /tmp/cmdline /etc/udev/saved.cmdline
+	mv /tmp/devices /etc/udev/saved.devices
+	mv /tmp/atags /etc/udev/saved.atags
+	echo
+else
+	rm -f /tmp/uname
+	rm -f /tmp/cmdline
+	rm -f /tmp/devices
+	rm -f /tmp/atags
 fi
 
 exit 0
diff --git a/meta/recipes-core/udev/udev/udev-cache.default b/meta/recipes-core/udev/udev/udev-cache.default
new file mode 100644
index 0000000..5c4937a
--- /dev/null
+++ b/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"
diff --git a/meta/recipes-core/udev/udev_164.bb b/meta/recipes-core/udev/udev_164.bb
index f952c90..c89eab4 100644
--- a/meta/recipes-core/udev/udev_164.bb
+++ b/meta/recipes-core/udev/udev_164.bb
@@ -1,6 +1,6 @@ 
 include udev.inc
 
-PR = "r8"
+PR = "r9"
 
 SRC_URI += "file://udev-166-v4l1-1.patch"