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by Francesco Paolo Lovergine
rules: linking manpages-posix not manpages. |
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved |
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by Francesco Paolo Lovergine
* Alligned to linux main manpages edition. |
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.TH "PTHREAD_CANCEL" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" |
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by Francesco Paolo Lovergine
rules: linking manpages-posix not manpages. |
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.\" pthread_cancel |
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.SH NAME |
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pthread_cancel \- cancel execution of a thread
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.SH SYNOPSIS |
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.LP
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\fB#include <pthread.h>
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.br
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.sp
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int pthread_cancel(pthread_t\fP \fIthread\fP\fB); \fP |
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\fB
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.br
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\fP
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.SH DESCRIPTION |
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.LP
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The \fIpthread_cancel\fP() function shall request that \fIthread\fP |
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be canceled. The target thread's cancelability state and |
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type determines when the cancellation takes effect. When the cancellation |
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is acted on, the cancellation cleanup handlers for |
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\fIthread\fP shall be called. When the last cancellation cleanup handler |
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returns, the thread-specific data destructor functions |
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shall be called for \fIthread\fP. When the last destructor function |
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returns, \fIthread\fP shall be terminated. |
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.LP
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The cancellation processing in the target thread shall run asynchronously |
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with respect to the calling thread returning from |
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\fIpthread_cancel\fP(). |
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.SH RETURN VALUE |
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.LP
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If successful, the \fIpthread_cancel\fP() function shall return zero; |
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otherwise, an error number shall be returned to indicate |
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the error. |
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.SH ERRORS |
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.LP
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The \fIpthread_cancel\fP() function may fail if: |
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.TP 7 |
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.B ESRCH |
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No thread could be found corresponding to that specified by the given |
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thread ID. |
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.sp
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.LP
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The \fIpthread_cancel\fP() function shall not return an error code |
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of [EINTR]. |
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.LP
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\fIThe following sections are informative.\fP |
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.SH EXAMPLES |
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.LP
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None. |
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.SH APPLICATION USAGE |
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.LP
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None. |
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.SH RATIONALE |
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.LP
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Two alternative functions were considered for sending the cancellation |
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notification to a thread. One would be to define a new |
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SIGCANCEL signal that had the cancellation semantics when delivered; |
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the other was to define the new \fIpthread_cancel\fP() |
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function, which would trigger the cancellation semantics. |
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.LP
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The advantage of a new signal was that so much of the delivery criteria |
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were identical to that used when trying to deliver a |
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signal that making cancellation notification a signal was seen as |
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consistent. Indeed, many implementations implement cancellation |
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using a special signal. On the other hand, there would be no signal |
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functions that could be used with this signal except \fIpthread_kill\fP(), |
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and the behavior of the delivered cancellation signal would be unlike |
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any previously existing defined signal. |
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.LP
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The benefits of a special function include the recognition that this |
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signal would be defined because of the similar delivery |
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criteria and that this is the only common behavior between a cancellation |
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request and a signal. In addition, the cancellation |
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delivery mechanism does not have to be implemented as a signal. There |
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are also strong, if not stronger, parallels with language |
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exception mechanisms than with signals that are potentially obscured |
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if the delivery mechanism is visibly closer to signals. |
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.LP
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In the end, it was considered that as there were so many exceptions |
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to the use of the new signal with existing signals functions |
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it would be misleading. A special function has resolved this problem. |
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This function was carefully defined so that an implementation |
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wishing to provide the cancellation functions on top of signals could |
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do so. The special function also means that implementations |
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are not obliged to implement cancellation with signals. |
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.SH FUTURE DIRECTIONS |
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.LP
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None. |
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.SH SEE ALSO |
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.LP
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\fIpthread_exit\fP() , \fIpthread_cond_timedwait\fP() , \fIpthread_join\fP() |
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, \fIpthread_setcancelstate\fP() , the Base Definitions volume of |
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IEEE\ Std\ 1003.1-2001, \fI<pthread.h>\fP |
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.SH COPYRIGHT |
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Portions of this text are reprinted and reproduced in electronic form |
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology |
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-- Portable Operating System Interface (POSIX), The Open Group Base |
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of |
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Electrical and Electronics Engineers, Inc and The Open Group. In the |
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event of any discrepancy between this version and the original IEEE and |
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The Open Group Standard, the original IEEE and The Open Group Standard |
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is the referee document. The original Standard can be obtained online at |
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http://www.opengroup.org/unix/online.html . |