pthreadsetcancelstate

pthread_setcancelstate is a POSIX Threads (pthreads) function that sets the cancelability state of the calling thread. It controls whether the thread can be canceled by cancellation requests. The function is declared as int pthread_setcancelstate(int state, int oldstate); and requires inclusion of pthread.h. The state argument must be either PTHREAD_CANCEL_ENABLE or PTHREAD_CANCEL_DISABLE. If oldstate is non-null, the function stores the thread’s previous cancelability state there.

When the state is PTHREAD_CANCEL_ENABLE, the thread may be canceled by a pending cancellation request. If a cancellation request has been issued and the thread reaches a cancellation point (in the case of deferred cancellation) or cancellation occurs immediately (in the case of asynchronous cancellation), the thread will be terminated and cleanup handlers will be invoked as defined by the cancellation semantics. When the state is PTHREAD_CANCEL_DISABLE, cancellation is inhibited for the calling thread; any cancellation requests are not immediately acted upon and may be held as pending until cancellation is enabled again and control reaches a cancellation point or the thread exits.

Cancellation behavior is determined in part by pthread_setcanceltype, which selects between DEFERRED and ASYNCHRONOUS cancellation. The enable/disable state only enables or disables cancellation regardless of type. Practically, programmers use this function to protect critical sections where a cancellation might leave resources in an inconsistent state. The function returns 0 on success; on error, it returns a nonzero error number, typically EINVAL if the state argument is invalid.