[FS#741] RB750r2 sysupgrade cant unmount Resource busy error

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Francis (francisuk1989) 

Attached to Project - LEDE Project
Summary - RB750r2 sysupgrade cant unmount Resource busy error
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Mikrotik RB750r2 (hEX lite)
Reboot (SNAPSHOT, r4049-9412fc2) The snapshot build dated 28/04/2017 (Europe timezone)

I first did a boot up on TFTP with **mikrotik-rb-nor-flash-16M-initramfs-kernel.bin** and then downloaded the **lede-ar71xx-mikrotik-rb-nor-flash-16M-squashfs-sysupgrade.bin** via wget into cd /tmp

Then i did sysupgrade lede-ar71xx-mikrotik-rb-nor-flash-16M-squashfs-sysupgrade.bin however everything seems to be installed ok but got theses following errors?
   

 root at LEDE:/tmp# sysupgrade lede-ar71xx-mikrotik-rb-nor-flash-16M-squashfs-sysupgrade.bin
Cannot save config while running from ramdisk.
killall: watchdog: no process killed
Unlocking firmware ...
Erasing firmware ...
Sending TERM to remaining processes ... udhcpc odhcp6c ntpd dnsmasq ubusd askfirst logd netifd odhcpd
Sending KILL to remaining processes ... askfirst
Performing system upgrade...
Unlocking firmware ..
Writing from  to firmware ...
Appending jffs2 data from /tmp/sysupgrade.tgz to firmware..
.File /tmp/sysupgrade.tgz does not exist
Upgrade completed
Rebooting system...
umount: can't unmount /dev/pts: Resource busy
umount: can't unmount /dev: Resource busy
umount: can't unmount /tmp: Resource busy
umount: can't unmount /: Invalid argument

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=741