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_cancel — cancel execution of a thread

SYNOPSIS

       #include <pthread.h>

       int pthread_cancel(pthread_t thread);

DESCRIPTION

       The  pthread_cancel()  function  shall request that thread be canceled. The target thread's cancelability
       state and type determines when the cancellation takes effect. When the  cancellation  is  acted  on,  the
       cancellation  cleanup  handlers  for  thread  shall be called. When the last cancellation cleanup handler
       returns, the thread-specific data destructor functions  shall  be  called  for  thread.   When  the  last
       destructor function returns, thread shall be terminated.

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

RETURN VALUE

       If successful, the pthread_cancel() function shall return zero;  otherwise,  an  error  number  shall  be
       returned to indicate the error.

ERRORS

       The pthread_cancel() function shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       Two  alternative  functions  were  considered  for sending the cancellation notification to a thread. One
       would be to define a new SIGCANCEL signal that had the cancellation semantics when delivered;  the  other
       was to define the new pthread_cancel() function, which would trigger the cancellation semantics.

       The  advantage of a new signal was that so much of the delivery criteria were identical to that used when
       trying to deliver a signal that making cancellation notification a signal was seen as consistent. Indeed,
       many implementations implement cancellation using a special signal. On the other hand, there would be  no
       signal  functions  that  could  be  used  with this signal except pthread_kill(), and the behavior of the
       delivered cancellation signal would be unlike any previously existing defined signal.

       The benefits of a special function include the recognition that this signal would be defined  because  of
       the  similar  delivery  criteria and that this is the only common behavior between a cancellation request
       and a signal. In addition, the cancellation delivery mechanism does not  have  to  be  implemented  as  a
       signal.  There  are  also strong, if not stronger, parallels with language exception mechanisms than with
       signals that are potentially obscured if the delivery mechanism is visibly closer to signals.

       In the end, it was considered that as there were so many exceptions to the use of  the  new  signal  with
       existing  signals  functions  it would be misleading. A special function has resolved this problem.  This
       function was carefully defined so that an implementation wishing to provide the cancellation functions on
       top of signals could do so.  The special function also means that  implementations  are  not  obliged  to
       implement cancellation with signals.

       If an implementation detects use of a thread ID after the end of its lifetime, it is recommended that the
       function should fail and report an [ESRCH] error.

FUTURE DIRECTIONS

       None.

SEE ALSO

       pthread_exit(), pthread_cond_timedwait(), pthread_join(), pthread_setcancelstate()

       The Base Definitions volume of POSIX.1‐2017, <pthread.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  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.opengroup.org/unix/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 .

IEEE/The Open Group                                   2017                                PTHREAD_CANCEL(3POSIX)