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12 .TH PTHREAD_RWLOCK_INIT 3C "Mar 23, 2005"
13 .SH NAME
14 pthread_rwlock_init, pthread_rwlock_destroy \- initialize or destroy read-write
15 lock object
16 .SH SYNOPSIS
17 .LP
18 .nf
19 cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
20 #include <pthread.h>
22 \fBint\fR \fBpthread_rwlock_init\fR(\fBpthread_rwlock_t *restrict\fR \fIrwlock\fR,
23 \fBconst pthread_rwlockattr_t *restrict\fR \fIattr\fR);
24 .fi
26 .LP
27 .nf
28 \fBint\fR \fBpthread_rwlock_destroy\fR(\fBpthread_rwlock_t *\fR\fI*rwlock\fR);
29 .fi
31 .LP
32 .nf
33 \fBpthread_rwlock_t\fR \fIrwlock\fR=\fBPTHREAD_RWLOCK_INITIALIZER\fR;
34 .fi
36 .SH DESCRIPTION
37 .sp
38 .LP
39 The \fBpthread_rwlock_init()\fR function initializes the read-write lock
40 referenced by \fIrwlock\fR with the attributes referenced by \fIattr\fR. If
41 \fIattr\fR is NULL, the default read-write lock attributes are used; the
42 effect is the same as passing the address of a default read-write lock
43 attributes object. Once initialized, the lock can be used any number of times
44 without being re-initialized. Upon successful initialization, the state of the
45 read-write lock becomes initialized and unlocked. Results are undefined if
46 \fBpthread_rwlock_init()\fR is called specifying an already initialized
47 read-write lock. Results are undefined if a read-write lock is used without
48 first being initialized.
49 .sp
50 .LP
51 If the \fBpthread_rwlock_init()\fR function fails, \fIrwlock\fR is not
52 initialized and the contents of \fIrwlock\fR are undefined.
53 .sp
54 .LP
55 The \fBpthread_rwlock_destroy()\fR function destroys the read-write lock object
56 referenced by \fIrwlock\fR and releases any resources used by the lock. The
57 effect of subsequent use of the lock is undefined until the lock is
58 re-initialized by another call to \fBpthread_rwlock_init()\fR. An
59 implementation may cause \fBpthread_rwlock_destroy()\fR to set the object
60 referenced by \fIrwlock\fR to an invalid value. Results are undefined if
61 \fBpthread_rwlock_destroy()\fR is called when any thread holds \fIrwlock\fR.
62 Attempting to destroy an uninitialized read-write lock results in undefined
63 behaviour. A destroyed read-write lock object can be re-initialized using
64 \fBpthread_rwlock_init()\fR; the results of otherwise referencing the
65 read-write lock object after it has been destroyed are undefined.
66 .sp
67 .LP
68 In cases where default read-write lock attributes are appropriate, the macro
69 \fBPTHREAD_RWLOCK_INITIALIZER\fR can be used to initialize read-write locks
70 that are statically allocated. The effect is equivalent to dynamic
71 initialization by a call to \fBpthread_rwlock_init()\fR with the parameter
72 \fIattr\fR specified as NULL, except that no error checks are performed.
73 .SH RETURN VALUES
74 .sp
75 .LP
76 If successful, the \fBpthread_rwlock_init()\fR and
77 \fBpthread_rwlock_destroy()\fR functions return \fB0\fR. Otherwise, an error
78 number is returned to indicate the error.
79 .SH ERRORS
80 .sp
81 .LP
82 The \fBpthread_rwlock_init()\fR and \fBpthread_rwlock_destroy()\fR functions
83 will fail if:
84 .sp
85 .ne 2
86 .na
87 \fB\fBEINVAL\fR\fR
88 .ad
89 .RS 10n
90 The value specified by \fIattr\fR is invalid.
91 .RE
93 .sp
94 .ne 2
95 .na
96 \fB\fBEINVAL\fR\fR
97 .ad
98 .RS 10n
99 The value specified by \fIrwlock\fR is invalid.
100 .RE
102 .SH ATTRIBUTES
103 .sp
104 .LP
105 See \fBattributes\fR(5) for descriptions of the following attributes:
106 .sp
108 .sp
109 .TS
110 box;
111 c | c
112 l | l .
113 ATTRIBUTE TYPE ATTRIBUTE VALUE
114 _
115 Interface Stability Standard
116 _
117 MT-Level MT-Safe
118 .TE
120 .SH SEE ALSO
121 .sp
122 .LP
123 \fBpthread_rwlock_rdlock\fR(3C), \fBpthread_rwlock_unlock\fR(3C),
124 \fBpthread_rwlock_wrlock\fR(3C), \fBpthread_rwlockattr_init\fR(3C),
125 \fBattributes\fR(5), \fBstandards\fR(5)