When plugging an iPhone to a Ubuntu machine for few times, the CPU becomes busy with 100% utilization.

This is due to some bugs which causes iphone-set-info and sometimes gvfs-afc-volume-monitor program to misbehave.

To fix this, run the following commands at the terminal

sudo killall -9 iphone-set-info
sudo killall -9 gvfs-afc-volume-monitor

This will only kill the programs, and will not affect the iPhone's charging.