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busybox: mdev: Ensure /dev/initctl exists after tmpfs mount

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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.

(From OE-Core rev: 53543363a8ab4424c17ed7aec0e8aefc4df86b3d)

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>
This commit is contained in:
Ben Shelton
2014-07-21 11:53:47 -05:00
committed by Richard Purdie
parent 034790df8f
commit acfe054e32
1 changed files with 10 additions and 0 deletions
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10
meta/recipes-core/busybox/files/mdev
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@@ -7,3 +7,13 @@ mount -t devpts devpts /dev/pts
touch /dev/mdev.seq
echo "/sbin/mdev" > /proc/sys/kernel/hotplug
mdev -s
#
# We might have mounted something over /dev, see if /dev/initctl is there.
#
if test ! -p /dev/initctl
then
rm -f /dev/initctl
mknod -m 600 /dev/initctl p
fi