udev-cache: stop race between sysconf and cache generation
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this, then the sysconf will be out of date with respect to the cache.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 <rich.tollerton@ni.com>
