bionic (3) pthread_cancel.3posix.gz

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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.1‐2008, <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 .