Here's a very simple workaround on how to fix frozen app store and 'softwareupdated' issues while installing the latest OS X Yosemite 10.10.4 or iTunes 12.2.
How to Fix Frozen App Store Updates & High softwareupdated CPU in OS X While Updating Your Macbook
All you need to do is fix it manually from the command line software update mechanism, which avoids the App Store.
First, if softwareupdate is consuming significant CPU, you can kill the process with the following Terminal command:
Next, you can install iTunes 12.2 update manually with the following command string:
softwareupdate -i iTunesXPatch-12.2
Once iTunes 12.2 installs and is no longer available as an update, everything else worked fine in the App Store.
For some users, the problem has persisted with the actual OS X 10.10.4 update as well.
For installing OS X 10.10.4, you can either attempt to update from the command line, or download and use the Combo Updater. Either way you’ll want to back up the Mac beforehand, like you would with any other system update.
The command to initiate the OS X 10.10.4 installation from the Terminal is as follows:
softwareupdate -i OSXUpd10.10.4-10.10.4
A restart is required to complete the installation.