Patchwork [3/4] busybox: mdev: Ensure /dev/initctl exists after tmpfs mount

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Submitter Ben Shelton
Date July 21, 2014, 4:53 p.m.
Message ID <1405961628-25284-3-git-send-email-ben.shelton@ni.com>
Download mbox | patch
Permalink /patch/76211/
State Accepted
Commit acfe054e32b9e60db3970d7546e759b37fde74c2
Headers show

Comments

Ben Shelton - July 21, 2014, 4:53 p.m.
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>
---
 meta/recipes-core/busybox/files/mdev | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch

diff --git a/meta/recipes-core/busybox/files/mdev b/meta/recipes-core/busybox/files/mdev
index c4447ef..9625247 100755
--- a/meta/recipes-core/busybox/files/mdev
+++ b/meta/recipes-core/busybox/files/mdev
@@ -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
+