bionic (3) pthread_setcancelstate.3posix.gz

Provided by: manpages-posix-dev_2013a-2_all bug

PROLOG
       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
       pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel — set cancelability state


SYNOPSIS
       #include <pthread.h>

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


DESCRIPTION
       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 PTHREAD_CANCEL_DISABLE.

       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 PTHREAD_CANCEL_ASYNCHRONOUS.

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

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


ERRORS
       The pthread_setcancelstate() function may fail if:

       EINVAL The specified state is not PTHREAD_CANCEL_ENABLE or PTHREAD_CANCEL_DISABLE.

       The pthread_setcanceltype() function may fail if:

       EINVAL The specified type is not PTHREAD_CANCEL_DEFERRED or PTHREAD_CANCEL_ASYNCHRONOUS.

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

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       None.


RATIONALE
       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.


FUTURE DIRECTIONS
       None.


SEE ALSO
       pthread_cancel()

       The Base Definitions volume of POSIX.1‐2008, <pthread.h>


       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
       http://www.unix.org/online.html .

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .