  We examine status updating systems in which time-stamped status updates are
stored/written in shared-memory. Specifically, we compare Read-Copy-Update
(RCU) and Readers-Writer lock (RWL) as shared-memory synchronization primitives
on the update freshness. To demonstrate the tension between readers and writers
accessing shared-memory, we consider a network scenario with a pair of coupled
updating processes. Location updates of a mobile terminal are written to a
shared-memory Forwarder Information Base (FIB) at a network forwarder. An
application server sends ``app updates'' to the mobile terminal via the
forwarder. Arriving app updates at forwarder are addressed (by reading the FIB)
and forwarded to the mobile terminal. If a FIB read returns an outdated
address, the misaddressed app update is lost in transit. We redesign these
reader and writer processes using preemption mechanisms that improve the
timeliness of updates. We present a Stochastic Hybrid System (SHS) framework to
analyze location and app update age processes and show how these two age
processes are coupled through synchronization primitives. Our analysis shows
that using a lock-based primitive (RWL) can serve fresher app updates to the
mobile terminal at higher location update rates while lock-less (RCU) mechanism
favors timely delivery of app updates at lower location update rates.
