1PTHREAD_CANCEL(P) POSIX Programmer's Manual PTHREAD_CANCEL(P)
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6 pthread_cancel - cancel execution of a thread
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9 #include <pthread.h>
10 int pthread_cancel(pthread_t thread);
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15 The pthread_cancel() function shall request that thread be canceled.
16 The target thread's cancelability state and type determines when the
17 cancellation takes effect. When the cancellation is acted on, the can‐
18 cellation cleanup handlers for thread shall be called. When the last
19 cancellation cleanup handler returns, the thread-specific data destruc‐
20 tor functions shall be called for thread. When the last destructor
21 function returns, thread shall be terminated.
22 The cancellation processing in the target thread shall run asyn‐
24 chronously with respect to the calling thread returning from
25 pthread_cancel().
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28 If successful, the pthread_cancel() function shall return zero; other‐
29 wise, an error number shall be returned to indicate the error.
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32 The pthread_cancel() function may fail if:
33 ESRCH No thread could be found corresponding to that specified by the
35 given thread ID.
36 The pthread_cancel() function shall not return an error code of
39 [EINTR].
40 The following sections are informative.
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44 None.
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47 None.
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50 Two alternative functions were considered for sending the cancellation
51 notification to a thread. One would be to define a new SIGCANCEL signal
52 that had the cancellation semantics when delivered; the other was to
53 define the new pthread_cancel() function, which would trigger the can‐
54 cellation semantics.
55 The advantage of a new signal was that so much of the delivery criteria
57 were identical to that used when trying to deliver a signal that making
58 cancellation notification a signal was seen as consistent. Indeed, many
59 implementations implement cancellation using a special signal. On the
60 other hand, there would be no signal functions that could be used with
61 this signal except pthread_kill(), and the behavior of the delivered
62 cancellation signal would be unlike any previously existing defined
63 signal.
64 The benefits of a special function include the recognition that this
66 signal would be defined because of the similar delivery criteria and
67 that this is the only common behavior between a cancellation request
68 and a signal. In addition, the cancellation delivery mechanism does not
69 have to be implemented as a signal. There are also strong, if not
70 stronger, parallels with language exception mechanisms than with sig‐
71 nals that are potentially obscured if the delivery mechanism is visibly
72 closer to signals.
73 In the end, it was considered that as there were so many exceptions to
75 the use of the new signal with existing signals functions it would be
76 misleading. A special function has resolved this problem. This func‐
77 tion was carefully defined so that an implementation wishing to provide
78 the cancellation functions on top of signals could do so. The special
79 function also means that implementations are not obliged to implement
80 cancellation with signals.
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83 None.
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86 pthread_exit() , pthread_cond_timedwait() , pthread_join() ,
87 pthread_setcancelstate() , the Base Definitions volume of
88 IEEE Std 1003.1-2001, <pthread.h>
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91 Portions of this text are reprinted and reproduced in electronic form
92 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
93 -- Portable Operating System Interface (POSIX), The Open Group Base
94 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
95 Electrical and Electronics Engineers, Inc and The Open Group. In the
96 event of any discrepancy between this version and the original IEEE and
97 The Open Group Standard, the original IEEE and The Open Group Standard
98 is the referee document. The original Standard can be obtained online
99 at http://www.opengroup.org/unix/online.html .
100IEEE/The Open Group 2003 PTHREAD_CANCEL(P)