Section: POSIX Programmer's Manual (3P)
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.
--- cancel execution of a thread
int pthread_cancel(pthread_t thread);
function shall request that
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
shall be called. When the last cancellation cleanup handler returns,
the thread-specific data destructor functions shall be called for
When the last destructor function returns,
shall be terminated.
The cancellation processing in the target thread shall run
asynchronously with respect to the calling thread returning from
If successful, the
function shall return zero; otherwise, an error number shall be
returned to indicate the error.
function shall not return an error code of
The following sections are informative.
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
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
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
The Base Definitions volume of POSIX.1-2008,
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
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