Peterson's 1981 two-process algorithm showed that mutual exclusion could be expressed with only ordinary shared variables—provided the memory model supplied the ordering guarantees the proof assumes.
Leslie Lamport's 1979 definition of sequential consistency gave shared-memory programmers a precise contract: concurrent execution should look like one interleaving that preserves each processor's program order.
POSIX.1c turned a fragmented collection of vendor thread packages into a portable Unix API for creating threads, synchronizing them, and building shared-memory applications across systems.
Non-uniform memory access architectures preserved a shared address space while admitting that memory latency depends on where data is physically located; Stanford DASH helped prove that coherent shared memory could scale beyond a single bus.
Leslie Lamport's 1974 bakery algorithm showed that mutual exclusion could be achieved using ordinary shared reads and writes, even under surprisingly weak assumptions about overlapping memory operations.
The MESI family of cache-coherence protocols let multiprocessors keep private copies of shared memory while preserving the illusion that processors still agree on the values of shared cache lines.
Monitors moved mutual exclusion and condition synchronization into structured program modules, helping make shared-memory concurrency easier to reason about.
OpenMP standardized directive-based parallel programming across Fortran, C and C++, giving shared-memory applications a portable path from serial loops to multicore execution.