Interthread

Interthread refers to communication and coordination between threads within the same process. It enables safe data exchange and task synchronization across multiple threads while avoiding the higher overhead and isolation boundaries of inter-process communication. Interthread communication relies on shared memory and explicit synchronization, since threads share the same address space.

Common mechanisms include shared memory guarded by synchronization primitives such as mutexes or atomic operations to protect access to shared data. Condition variables and semaphores are used for signaling state changes or coordinating sequencing. Thread-safe queues or buffers provide a safe conduit for passing data between producers and consumers. Higher-level abstractions such as futures, promises, or channels (present in several languages) can simplify asynchronous communication and result retrieval. Memory visibility and ordering rely on proper use of these primitives to establish happens-before relationships.

Typical patterns in interthread communication include the producer-consumer model using a bounded or unbounded queue, barrier synchronization to align phases of computation, reader-writer locks for concurrent access to shared resources, and thread pools to distribute work among multiple threads efficiently.

Design considerations emphasize avoiding data races, deadlocks, and livelocks. Developers should minimize lock contention, prefer finer-grained locking or lock-free data structures where appropriate, and ensure that long-running I/O or blocking operations do not hold locks. Where possible, higher-level concurrency abstractions can reduce complexity and errors.

Interthread communication is distinct from inter-process communication, as it occurs within a single process and typically offers lower latency and overhead but requires careful synchronization to maintain correctness. It is a core topic in multithreaded programming across languages including Java, C++, Go, and Rust.