pthreadkill

pthreadkill is not a standard POSIX API. In common usage, the term may refer informally to sending a signal to a specific thread using the POSIX function pthread_kill, or to a project-specific wrapper named pthreadkill. There is no official function named pthreadkill in the POSIX threads (libpthread) specification.

Standard background and behavior

pthread_kill exists to deliver a signal to a single thread within a process. The typical usage is int pthread_kill(pthread_t thread, int sig); on success it returns 0, and on error it returns a nonzero error code (for example, ESRCH if the thread cannot be found or EINVAL for an invalid signal). The signal is delivered to the specified thread, and the effect depends on the signal’s disposition on that thread. If a handler is installed for the signal on that thread, the handler runs; otherwise the default action for the signal is performed, which may terminate the process or have other effects.

Considerations and safety

Delivering signals to individual threads is asynchronous and can interrupt critical sections. Signals should be used with care; ensure that appropriate handlers are installed, that shared data is protected, and that cancellation or termination semantics are well understood. Signals may interact with thread cancellation points and with resource cleanup routines.

Alternatives and patterns

For cooperative thread termination, pthread_cancel or a controlled shutdown flag is often preferable. In some designs, a dedicated worker thread monitors termination requests through a thread-safe queue or condition variables rather than relying on signals.

See also

POSIX threads, pthread_kill, pthread_cancel, signal handling.