PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel —
       set cancelability state

SYNOPSIS         top

       #include <pthread.h>

       int pthread_setcancelstate(int state, int *oldstate);
       int pthread_setcanceltype(int type, int *oldtype);
       void pthread_testcancel(void);

DESCRIPTION         top

       The pthread_setcancelstate() function shall atomically both set the
       calling thread's cancelability state to the indicated state and
       return the previous cancelability state at the location referenced by
       oldstate.  Legal values for state are PTHREAD_CANCEL_ENABLE and

       The pthread_setcanceltype() function shall atomically both set the
       calling thread's cancelability type to the indicated type and return
       the previous cancelability type at the location referenced by
       oldtype.  Legal values for type are PTHREAD_CANCEL_DEFERRED and

       The cancelability state and type of any newly created threads,
       including the thread in which main() was first invoked, shall be

       The pthread_testcancel() function shall create a cancellation point
       in the calling thread. The pthread_testcancel() function shall have
       no effect if cancelability is disabled.

RETURN VALUE         top

       If successful, the pthread_setcancelstate() and
       pthread_setcanceltype() functions shall return zero; otherwise, an
       error number shall be returned to indicate the error.

ERRORS         top

       The pthread_setcancelstate() function may fail if:

       EINVAL The specified state is not PTHREAD_CANCEL_ENABLE or

       The pthread_setcanceltype() function may fail if:

       EINVAL The specified type is not PTHREAD_CANCEL_DEFERRED or

       These functions shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES         top




RATIONALE         top

       The pthread_setcancelstate() and pthread_setcanceltype() functions
       control the points at which a thread may be asynchronously canceled.
       For cancellation control to be usable in modular fashion, some rules
       need to be followed.

       An object can be considered to be a generalization of a procedure. It
       is a set of procedures and global variables written as a unit and
       called by clients not known by the object. Objects may depend on
       other objects.

       First, cancelability should only be disabled on entry to an object,
       never explicitly enabled. On exit from an object, the cancelability
       state should always be restored to its value on entry to the object.

       This follows from a modularity argument: if the client of an object
       (or the client of an object that uses that object) has disabled
       cancelability, it is because the client does not want to be concerned
       about cleaning up if the thread is canceled while executing some
       sequence of actions. If an object is called in such a state and it
       enables cancelability and a cancellation request is pending for that
       thread, then the thread is canceled, contrary to the wish of the
       client that disabled.

       Second, the cancelability type may be explicitly set to either
       deferred or asynchronous upon entry to an object. But as with the
       cancelability state, on exit from an object the cancelability type
       should always be restored to its value on entry to the object.

       Finally, only functions that are cancel-safe may be called from a
       thread that is asynchronously cancelable.



SEE ALSO         top


       The Base Definitions volume of POSIX.1‐2008, pthread.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see .

IEEE/The Open Group                 2013          PTHREAD_SETCANCELSTATE(3P)