1PTHREAD_SETCANCELSTATE(3P) POSIX Programmer's ManualPTHREAD_SETCANCELSTATE(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel - set
13 cancelability state
14
16 #include <pthread.h>
17 int pthread_setcancelstate(int state, int *oldstate);
19 int pthread_setcanceltype(int type, int *oldtype);
20 void pthread_testcancel(void);
21
24 The pthread_setcancelstate() function shall atomically both set the
25 calling thread's cancelability state to the indicated state and return
26 the previous cancelability state at the location referenced by old‐
27 state. Legal values for state are PTHREAD_CANCEL_ENABLE and
28 PTHREAD_CANCEL_DISABLE.
29 The pthread_setcanceltype() function shall atomically both set the
31 calling thread's cancelability type to the indicated type and return
32 the previous cancelability type at the location referenced by oldtype.
33 Legal values for type are PTHREAD_CANCEL_DEFERRED and PTHREAD_CAN‐
34 CEL_ASYNCHRONOUS.
35 The cancelability state and type of any newly created threads, includ‐
37 ing the thread in which main() was first invoked, shall be PTHREAD_CAN‐
38 CEL_ENABLE and PTHREAD_CANCEL_DEFERRED respectively.
39 The pthread_testcancel() function shall create a cancellation point in
41 the calling thread. The pthread_testcancel() function shall have no
42 effect if cancelability is disabled.
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45 If successful, the pthread_setcancelstate() and pthread_setcanceltype()
46 functions shall return zero; otherwise, an error number shall be
47 returned to indicate the error.
48
50 The pthread_setcancelstate() function may fail if:
51 EINVAL The specified state is not PTHREAD_CANCEL_ENABLE or PTHREAD_CAN‐
53 CEL_DISABLE.
54 The pthread_setcanceltype() function may fail if:
57 EINVAL The specified type is not PTHREAD_CANCEL_DEFERRED or
59 PTHREAD_CANCEL_ASYNCHRONOUS.
60 These functions shall not return an error code of [EINTR].
63 The following sections are informative.
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67 None.
68
70 None.
71
73 The pthread_setcancelstate() and pthread_setcanceltype() functions con‐
74 trol the points at which a thread may be asynchronously canceled. For
75 cancellation control to be usable in modular fashion, some rules need
76 to be followed.
77 An object can be considered to be a generalization of a procedure. It
79 is a set of procedures and global variables written as a unit and
80 called by clients not known by the object. Objects may depend on other
81 objects.
82 First, cancelability should only be disabled on entry to an object,
84 never explicitly enabled. On exit from an object, the cancelability
85 state should always be restored to its value on entry to the object.
86 This follows from a modularity argument: if the client of an object (or
88 the client of an object that uses that object) has disabled cancelabil‐
89 ity, it is because the client does not want to be concerned about
90 cleaning up if the thread is canceled while executing some sequence of
91 actions. If an object is called in such a state and it enables cancela‐
92 bility and a cancellation request is pending for that thread, then the
93 thread is canceled, contrary to the wish of the client that disabled.
94 Second, the cancelability type may be explicitly set to either deferred
96 or asynchronous upon entry to an object. But as with the cancelability
97 state, on exit from an object the cancelability type should always be
98 restored to its value on entry to the object.
99 Finally, only functions that are cancel-safe may be called from a
101 thread that is asynchronously cancelable.
102
104 None.
105
107 pthread_cancel(), the Base Definitions volume of IEEE Std 1003.1-2001,
108 <pthread.h>
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111 Portions of this text are reprinted and reproduced in electronic form
112 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
113 -- Portable Operating System Interface (POSIX), The Open Group Base
114 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
115 Electrical and Electronics Engineers, Inc and The Open Group. In the
116 event of any discrepancy between this version and the original IEEE and
117 The Open Group Standard, the original IEEE and The Open Group Standard
118 is the referee document. The original Standard can be obtained online
119 at http://www.opengroup.org/unix/online.html .
120IEEE/The Open Group 2003 PTHREAD_SETCANCELSTATE(3P)