The validity of the udev cache is determined by the sysconf file (/etc/udev/cache.data). Currently, there is a substantial delay between sysconf generation in /etc/init.d/udev and cache generation in /etc/init.d/udev-cache. If a hotplug event arrives in the middle of this, then the sysconf will be out of date with respect to the cache.
The solution is two-pronged. First, we minimize the race window by regenerating the sysconf immediately before the cache, in /etc/init.d/udev-cache. This allows us to kill the race entirely by stopping the udev event queue while the sysconf and cache are being generated. Signed-off-by: Richard Tollerton <[email protected]> --- meta/recipes-core/udev/udev/udev-cache | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/meta/recipes-core/udev/udev/udev-cache b/meta/recipes-core/udev/udev/udev-cache index 497d257..a1410f5 100644 --- a/meta/recipes-core/udev/udev/udev-cache +++ b/meta/recipes-core/udev/udev/udev-cache @@ -19,8 +19,22 @@ export TZ=/etc/localtime DEVCACHE_TMP="/dev/shm/udev-cache-tmp.tar" SYSCONF_CACHED="/etc/udev/cache.data" SYSCONF_TMP="/dev/shm/udev.cache" + +# A list of files which are used as a criteria to judge whether the udev cache could be reused. +CMP_FILE_LIST="/proc/version /proc/cmdline /proc/devices /proc/atags" [ -f /etc/default/udev-cache ] && . /etc/default/udev-cache +readfiles () { + READDATA="" + for filename in $@; do + if [ -r $filename ]; then + while read line; do + READDATA="$READDATA$line" + done < $filename + fi + done +} + if [ "$ROOTFS_READ_ONLY" = "yes" ]; then [ "$VERBOSE" != "no" ] && echo "udev-cache: read-only rootfs, skip generating udev-cache" exit 0 @@ -28,11 +42,15 @@ fi if [ "$DEVCACHE" != "" -a -e "$SYSCONF_TMP" ]; then echo "Populating dev cache" + udevadm control --stop-exec-queue + readfiles $CMP_FILE_LIST + echo "$READDATA" > "$SYSCONF_TMP" find /dev -xdev \( -type b -o -type c -o -type l \) | cut -c 2- \ | xargs tar cf "${DEVCACHE_TMP}" -T- gzip < "${DEVCACHE_TMP}" > "$DEVCACHE" rm -f "${DEVCACHE_TMP}" mv "$SYSCONF_TMP" "$SYSCONF_CACHED" + udevadm control --start-exec-queue fi exit 0 -- 2.1.3 -- _______________________________________________ Openembedded-core mailing list [email protected] http://lists.openembedded.org/mailman/listinfo/openembedded-core
