tree 85527c3ea1f78c35eaf02df1c0584f16a88d9511
parent ee2ba19cec96347d11e3661077ef3c4c0eb068c2
author Pau Espin Pedrol <pespin@sysmocom.de> 1568393768 +0200
committer Pau Espin Pedrol <pespin@sysmocom.de> 1568999842 +0200

radioInterface: Atomically fetch and change underrun variable

Otherwise, it could happen that underrun events are lost:
TxLower (isUnderrun):	RxLower (pullBuffer):
read(underrun)
			read(underrun)
			write(underrun, |val) [maybe underrun becomes TRUE]
write(underrun, false)

Similary, it could happen the other direction if atomic was only applied
to isUnderrun:
TxLower (isUnderrun):	RxLower (pullBuffer):
			read(underrun) -> true
read(underrun)-> true
write(underrun, false)
			write(underrun, true|val) where val=false

So in here isUnderrun would return true twice while it should only
return one.

Change-Id: I684e0a5d2a9583a161d5a6593559b3a9e7cd57e3