'\" et

.TH PTHREAD_CANCEL "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH 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.

.SH NAME

pthread_cancel

\(em cancel execution of a thread

.SH SYNOPSIS

.LP

.nf

#include <pthread.h>

.P

int pthread_cancel(pthread_t \fIthread\fP);

.fi

.SH DESCRIPTION

The

\fIpthread_cancel\fR()

function shall request that

.IR 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

.IR thread

shall be called. When the last cancellation cleanup handler returns,

the thread-specific data destructor functions shall be called for

.IR thread .

When the last destructor function returns,

.IR thread

shall be terminated.

.P

The cancellation processing in the target thread shall run

asynchronously with respect to the calling thread returning from

\fIpthread_cancel\fR().

.SH "RETURN VALUE"

If successful, the

\fIpthread_cancel\fR()

function shall return zero; otherwise, an error number shall be

returned to indicate the error.

.SH ERRORS

The

\fIpthread_cancel\fR()

function shall not return an error code of

.BR [EINTR] .

.LP

.IR "The following sections are informative."

.SH EXAMPLES

None.

.SH "APPLICATION USAGE"

None.

.SH 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

\fIpthread_cancel\fR()

function, which would trigger the cancellation semantics.

.P

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

\fIpthread_kill\fR(),

and the behavior of the delivered cancellation signal would be unlike

any previously existing defined signal.

.P

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.

.P

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.

.P

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

.BR [ESRCH] 

error.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.ad l

.IR "\fIpthread_exit\fR\^(\|)",

.IR "\fIpthread_cond_timedwait\fR\^(\|)",

.IR "\fIpthread_join\fR\^(\|)",

.IR "\fIpthread_setcancelstate\fR\^(\|)"

.ad b

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<pthread.h>\fP"

.SH COPYRIGHT

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 .