syslog GPU errors when running multiple BRP4G tasks

Running the amd gpupro (all versions 16.30, 16.30.3 and the recent 16.40) on Ubuntu 16.04 and RX-480 GPU.  This host

The syslog has an entry every few seconds when running two BRP4G tasks (0.5)

see sample

Leaving only ONE task running - stops the errors.

I don't know where to look to find out what exactly a GPU fault 147 is, a bit of googling showed the bitcoin community had come across this error and fixed it here Ethereum - fixed faux GPU failures

Looking over the code there seems to be a change to the locking and unlocking calls.

I'll probably leave this running at 1.0 for a while to see if there is a change in this host's invalid rate.