busybox: mdev: Ensure /dev/initctl exists after tmpfs mount
During boot, there is a brief window during which /dev/initctl is
missing, which breaks initscripts that would need to access it. This
occurs because /etc/init.d/mountall.sh (rcS.d/S02...) attempts to ensure
/dev/initctl is present, but /etc/init.d/mdev (rcS.d/S06...) mounts over
/dev and clobbers the work done by mountall, and then does not wait
synchronously until initctl is ready before continuing.
To close this window, in /etc/init.d/mdev, we check whether /dev/initctl
is present, and if not, we remove it and recreate it. This is the same
thing that is done by /etc/init.d/mountall.sh, and we have verified that
any writers of /dev/initctl will wait synchronously until sysvinit
notices the change in fd and does the read, so no race exists.
Signed-off-by: Richard Tollerton <rich.tollerton@ni.com> Signed-off-by: Ben Shelton <ben.shelton@ni.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
