Manual browser: pthread_cancel(3)

PTHREAD_CANCEL(3) Library Functions Manual PTHREAD_CANCEL(3)


pthread_cancelcancel execution of a thread


POSIX Threads Library (libpthread, -lpthread)


#include <pthread.h>

pthread_cancel(pthread_t thread);


The pthread_cancel() function requests that thread be canceled. The target thread's cancelability state and type determines whether and when the target thread reacts to the cancellation request.
  1. The cancelability state of a thread is determined by the pthread_setcancelstate(3) function. The state can be either:
    • PTHREAD_CANCEL_ENABLE: the cancelability type determines when the actual cancellation occurs. This is the default.
    • PTHREAD_CANCEL_DISABLE: the request from pthread_cancel() remains queued until the cancellation is enabled by the thread.
  2. The cancellation type of a thread is determined by the pthread_setcanceltype(3) function. The type can be either:
    • PTHREAD_CANCEL_DEFERRED: the cancellation will be delayed until the thread calls a function that is a cancellation point. This is the default. The available cancellation points are listed in pthread_setcanceltype(3).
    • PTHREAD_CANCEL_ASYNCHRONOUS: the thread can be canceled at any time.

When the thread reacts to the cancellation request, the following occur:

  1. The cancellation cleanup handlers for the thread are called; see pthread_cleanup_push(3).
  2. When the last cancellation cleanup handler returns, the thread-specific data destructor functions will be called for the thread.
  3. When the last destructor function returns, the thread will be terminated; see pthread_exit(3).

The cancellation processing in the target thread runs asynchronously with respect to the calling thread returning from pthread_cancel().

A status of PTHREAD_CANCELED is made available to any threads joining with the target. The symbolic constant PTHREAD_CANCELED expands to a constant expression of type (void *), whose value matches no pointer to an object in memory nor the value NULL.


If successful, the pthread_cancel() functions will return zero. Otherwise an error number will be returned to indicate the error.


The pthread_cancel() function may fail if:
No thread could be found corresponding to that specified by the given thread ID.


The function conforms to IEEE Std 1003.1-2001 (“POSIX.1”).
July 9, 2010 NetBSD 7.0