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.TH PTHREAD_RWLOCK_DESTROY "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_rwlock_destroy,

pthread_rwlock_init

\(em destroy and initialize a read-write lock object

.SH SYNOPSIS

.LP

.nf

#include <pthread.h>

.P

int pthread_rwlock_destroy(pthread_rwlock_t *\fIrwlock\fP);

int pthread_rwlock_init(pthread_rwlock_t *restrict \fIrwlock\fP,

    const pthread_rwlockattr_t *restrict \fIattr\fP);

pthread_rwlock_t \fIrwlock\fR = PTHREAD_RWLOCK_INITIALIZER;

.fi

.SH DESCRIPTION

The

\fIpthread_rwlock_destroy\fR()

function shall destroy the read-write lock object referenced by

.IR rwlock

and release any resources used by the lock. The effect of subsequent

use of the lock is undefined until the lock is reinitialized by

another call to

\fIpthread_rwlock_init\fR().

An implementation may cause

\fIpthread_rwlock_destroy\fR()

to set the object referenced by

.IR rwlock

to an invalid value. Results are undefined if

\fIpthread_rwlock_destroy\fR()

is called when any thread holds

.IR rwlock .

Attempting to destroy an uninitialized read-write lock results in

undefined behavior.

.P

The

\fIpthread_rwlock_init\fR()

function shall allocate any resources required to use the read-write

lock referenced by

.IR rwlock

and initializes the lock to an unlocked state with attributes

referenced by

.IR attr .

If

.IR attr

is NULL, the default read-write lock attributes shall be used; the

effect is the same as passing the address of a default read-write lock

attributes object. Once initialized, the lock can be used any number of

times without being reinitialized. Results are undefined if

\fIpthread_rwlock_init\fR()

is called specifying an already initialized read-write lock. Results

are undefined if a read-write lock is used without first being

initialized.

.P

If the

\fIpthread_rwlock_init\fR()

function fails,

.IR rwlock

shall not be initialized and the contents of

.IR rwlock

are undefined.

.P

Only the object referenced by

.IR rwlock

may be used for performing synchronization. The result of referring to

copies of that object in calls to

\fIpthread_rwlock_destroy\fR(),

\fIpthread_rwlock_rdlock\fR(),

\fIpthread_rwlock_timedrdlock\fR(),

\fIpthread_rwlock_timedwrlock\fR(),

\fIpthread_rwlock_tryrdlock\fR(),

\fIpthread_rwlock_trywrlock\fR(),

\fIpthread_rwlock_unlock\fR(),

or

\fIpthread_rwlock_wrlock\fR()

is undefined.

.P

In cases where default read-write lock attributes are appropriate, the

macro PTHREAD_RWLOCK_INITIALIZER can be used to initialize read-write

locks. The effect shall be equivalent to dynamic initialization by a

call to

\fIpthread_rwlock_init\fR()

with the

.IR attr

parameter specified as NULL, except that no error checks are performed.

.P

The behavior is undefined if the value specified by the

.IR attr

argument to

\fIpthread_rwlock_init\fR()

does not refer to an initialized read-write lock attributes object.

.SH "RETURN VALUE"

If successful, the

\fIpthread_rwlock_destroy\fR()

and

\fIpthread_rwlock_init\fR()

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

returned to indicate the error.

.SH ERRORS

The

\fIpthread_rwlock_init\fR()

function shall fail if:

.TP

.BR EAGAIN

The system lacked the necessary resources (other than memory) to

initialize another read-write lock.

.TP

.BR ENOMEM

Insufficient memory exists to initialize the read-write lock.

.TP

.BR EPERM

The caller does not have the privilege to perform the operation.

.P

These functions shall not return an error code of

.BR [EINTR] .

.LP

.IR "The following sections are informative."

.SH EXAMPLES

None.

.SH "APPLICATION USAGE"

Applications using these and related read-write lock functions may be

subject to priority inversion, as discussed in the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 3.287" ", " "Priority Inversion".

.SH RATIONALE

If an implementation detects that the value specified by the

.IR rwlock

argument to

\fIpthread_rwlock_destroy\fR()

does not refer to an initialized read-write lock object, it is

recommended that the function should fail and report an

.BR [EINVAL] 

error.

.P

If an implementation detects that the value specified by the

.IR attr

argument to

\fIpthread_rwlockr_init\fR()

does not refer to an initialized read-write lock attributes object,

it is recommended that the function should fail and report an

.BR [EINVAL] 

error.

.P

If an implementation detects that the value specified by the

.IR rwlock

argument to

\fIpthread_rwlock_destroy\fR()

or

\fIpthread_rwlock_init\fR()

refers to a locked read-write lock object, or detects that the value

specified by the

.IR rwlock

argument to

\fIpthread_rwlock_init\fR()

refers to an already initialized read-write lock object, it is recommended

that the function should fail and report an

.BR [EBUSY] 

error.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.ad l

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

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

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

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

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

.ad b

.P

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

.IR "Section 3.287" ", " "Priority Inversion",

.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 .