Pthread

Pthreads, short for POSIX threads, is a portable multi-threading API defined by the POSIX standard (IEEE Std 1003.1c) for C and C++. It provides facilities for creating and terminating threads, synchronizing their access to shared data, and managing thread-specific state. Pthreads is a common foundation for concurrent programming on Unix-like systems and is supported on many other platforms, sometimes via vendor-specific wrappers on Windows.

Key types and objects include pthread_t for thread identifiers, pthread_attr_t for thread attributes, and synchronization primitives such as pthread_mutex_t for mutexes, pthread_cond_t for condition variables, and pthread_rwlock_t for read-write locks. Thread creation is performed with pthread_create, which can take an optional attributes object, a start routine, and an argument. Threads can be joined with pthread_join to obtain a return value, or detached with pthread_detach to allow automatic reclamation. Threads may be canceled using pthread_cancel, with cleanup handlers and deferred cancellation providing safe termination.

Additional features include thread-local storage via pthread_key_t and associated functions, and one-time initialization through pthread_once. Barriers via pthread_barrier_t and, on some systems, spinlocks via pthread_spinlock_t are available in various implementations. POSIX also defines mutex types (normal, error-checking, and recursive) and robust mutexes to support recovery after process crashes.

Scheduling and real-time control are supported through pthread_setschedparam and related attributes, enabling policies such as SCHED_FIFO, SCHED_RR, and SCHED_OTHER and priority adjustments. While pthreads aim for broad portability, some features vary by platform. Developers should be mindful of synchronization pitfalls such as deadlocks and priority inversion, and may use higher-level abstractions like thread pools to manage concurrency more efficiently.