pthread_cancel

PTHREAD_CANCEL(3POSIX)      POSIX Programmer's Manual     PTHREAD_CANCEL(3POSIX)



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)