pthread_testcancel

- create cancellation point in the calling thread

Synopsis

cc –mt [ flag... ] file... [ library... ]
#include <pthread.h>

void pthread_testcancel(void);

Description

The pthread_testcancel() function forces testing for cancellation. This is useful when you need to execute code that runs for long periods without encountering cancellation points; such as a library routine that executes long-running computations without cancellation points. This type of code can block cancellation for unacceptable long periods of time. One strategy for avoiding blocking cancellation for long periods, is to insert calls to pthread_testcancel() in the long-running computation code and to setup a cancellation handler in the library code, if required.

Return Values

The pthread_testcancel() function returns void.

Errors

The pthread_testcancel() function does not return errors.

Examples

See cancellation(5) for an example of using pthread_testcancel() to force testing for cancellation and a discussion of cancellation concepts.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

Intro(3), pthread_cleanup_pop(3C), pthread_cleanup_push(3C), pthread_exit(3C), pthread_join(3C), pthread_setcancelstate(3C), pthread_setcanceltype(3C), setjmp(3C), attributes(5), cancellation(5), condition(5), standards(5)

Notes

The pthread_testcancel() function has no effect if cancellation is disabled.

Use pthread_testcancel() with pthread_setcanceltype() called with its canceltype set to PTHREAD_CANCEL_DEFERRED. The pthread_testcancel() function operation is undefined if pthread_setcanceltype() was called with its canceltype argument set to PTHREAD_CANCEL_ASYNCHRONOUS.

It is possible to kill a thread when it is holding a resource, such as lock or allocated memory. If that thread has not setup a cancellation cleanup handler to release the held resource, the application is "cancel-unsafe". See attributes(5) for a discussion of Cancel-Safety, Deferred-Cancel-Safety, and Asynchronous-Cancel-Safety.