NAME

pthread_cancel − Allows a thread to request a thread to terminate execution

SYNOPSIS

#include <pthread.h>
int pthread_cancel(
        pthread_t thread );

LIBRARY

DECthreads POSIX 1003.1c Library (libpthread.so)

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS

thread
Thread that receives a cancellation request.

DESCRIPTION

This routine sends a cancellation request to the specified target thread. A cancellation request is a mechanism by which a calling thread requests the target thread to terminate as quickly as possible. Issuing a cancellation request does not guarantee that the target thread will receive or handle the request. 

When the cancellation request is acted on, all active cleanup handler routines for the target thread are called. When the last cleanup handler returns, the thread-specific data destructor routines are called for each thread-specific data key with a destructor and for which the target thread has a non-NULL value. Finally, the target thread is terminated. 

Note that cancellation of the target thread runs asynchronously with respect to the calling thread’s returning from pthread_cancel(3).  The target thread’s cancelability state and type determine when or if the cancellation takes place, as follows:

       •The target thread can delay cancellation during critical operations by setting its cancelability state to PTHREAD_CANCEL_DISABLE. 

       •Because of communication delays, the calling thread can only rely on the fact that a cancellation request will eventually become pending in the target thread (provided that the target thread does not terminate beforehand). 

       •The calling thread has no guarantee that a pending cancellation request will be delivered because delivery is controlled by the target thread. 

When a cancellation request is delivered to a thread, termination processing is similar to that for pthread_exit(3). For more information about thread termination, see the discussion of thread termination in pthread_create(3). 

This routine is preferred in implementing an Ada abort statement and any other language- or software-defined construct for requesting thread cancellation. 

The results of this routine are unpredictable, if the value specified in thread refers to a thread that does not currently exist. 

RETURN VALUES

If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows:

0Successful completion. 

[EINVAL]
The specified thread is invalid.

[ESRCH]
The thread argument does not specify an existing thread. 

ERRORS

None

SEE ALSO

Functions: pthread_cleanup_pop(3), pthread_cleanup_push(3), pthread_create(3), pthread_exit(3), pthread_join(3), pthread_setcancelstate(3), pthread_setcanceltype(3), pthread_testcancel(3)

Manuals: Guide to DECthreads and Programmer’s Guide