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| <H4>POSIX Threads for Windows – REFERENCE - <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A></H4> | |
| <P><A HREF="index.html">Reference Index</A></P> | |
| <P><A HREF="#toc">Table of Contents</A></P> | |
| <H2><A HREF="#toc0" NAME="sect0">Name</A></H2> | |
| <P>pthread_rwlock_destroy, pthread_rwlock_init - destroy and | |
| initialize a read-write lock object | |
| </P> | |
| <H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> | |
| <P><B>#include <pthread.h> </B> | |
| </P> | |
| <P><B>pthread_wrlock_t </B><I>rwlock</I> <B>= | |
| PTHREAD_RWLOCK_INITIALIZER;</B></P> | |
| <P><B>int pthread_rwlock_destroy(pthread_rwlock_t *</B><I>rwlock</I><B>); | |
| <BR>int pthread_rwlock_init(pthread_rwlock_t *restrict</B> <I>rwlock</I><B>, | |
| const pthread_rwlockattr_t *restrict</B> <I>attr</I><B>); </B> | |
| </P> | |
| <H2><A HREF="#toc2" NAME="sect2">Description</A></H2> | |
| <P>The <B>pthread_rwlock_destroy</B> function shall destroy the | |
| read-write lock object referenced by <I>rwlock</I> 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 | |
| <B>pthread_rwlock_init</B>. An implementation may cause | |
| <B>pthread_rwlock_destroy</B> to set the object referenced by <I>rwlock</I> | |
| to an invalid value. Results are undefined if <B>pthread_rwlock_destroy</B> | |
| is called when any thread holds <I>rwlock</I>. Attempting to destroy | |
| an uninitialized read-write lock results in undefined behavior. | |
| </P> | |
| <P>The <B>pthread_rwlock_init</B> function shall allocate any | |
| resources required to use the read-write lock referenced by <I>rwlock</I> | |
| and initializes the lock to an unlocked state with attributes | |
| referenced by <I>attr</I>. If <I>attr</I> 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 <B>pthread_rwlock_init</B> | |
| is called specifying an already initialized read-write lock. Results | |
| are undefined if a read-write lock is used without first being | |
| initialized. | |
| </P> | |
| <P>If the <B>pthread_rwlock_init</B> function fails, <I>rwlock</I> | |
| shall not be initialized and the contents of <I>rwlock</I> are | |
| undefined. | |
| </P> | |
| <P><B>Pthreads-w32</B> supports statically initialized <I>rwlock</I> | |
| objects using <B>PTHREAD_RWLOCK_INITIALIZER</B>. <SPAN STYLE="font-weight: medium"> | |
| An application should still call <B>pthread_rwlock_destroy</B> at | |
| some point to ensure that any resources consumed by the read/write | |
| lock are released.</SPAN></P> | |
| <P>Only the object referenced by <I>rwlock</I> may be used for | |
| performing synchronization. The result of referring to copies of that | |
| object in calls to <B>pthread_rwlock_destroy</B> , | |
| <B>pthread_rwlock_rdlock</B> , <B>pthread_rwlock_timedrdlock</B> , | |
| <B>pthread_rwlock_timedwrlock</B> , <B>pthread_rwlock_tryrdlock</B> , | |
| <B>pthread_rwlock_trywrlock</B> , <B>pthread_rwlock_unlock</B> , or | |
| <B>pthread_rwlock_wrlock</B> is undefined. | |
| </P> | |
| <P><B>Pthreads-w32</B> defines <B>_POSIX_READER_WRITER_LOCKS</B> in | |
| pthread.h as 200112L to indicate that the reader/writer routines are | |
| implemented and may be used.</P> | |
| <H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2> | |
| <P>If successful, the <B>pthread_rwlock_destroy</B> and | |
| <B>pthread_rwlock_init</B> functions shall return zero; otherwise, an | |
| error number shall be returned to indicate the error. | |
| </P> | |
| <P>The [EBUSY] and [EINVAL] error checks, if implemented, act as if | |
| they were performed immediately at the beginning of processing for | |
| the function and caused an error return prior to modifying the state | |
| of the read-write lock specified by <I>rwlock</I>. | |
| </P> | |
| <H2><A HREF="#toc4" NAME="sect4">Errors</A></H2> | |
| <P>The <B>pthread_rwlock_destroy</B> function may fail if: | |
| </P> | |
| <DL> | |
| <DT><B>EBUSY</B> | |
| </DT><DD> | |
| The implementation has detected an attempt to destroy the object | |
| referenced by <I>rwlock</I> while it is locked. | |
| </DD><DT> | |
| <B>EINVAL</B> | |
| </DT><DD STYLE="margin-bottom: 0.5cm"> | |
| The value specified by <I>rwlock</I> is invalid. | |
| </DD></DL> | |
| <P> | |
| The <B>pthread_rwlock_init</B> function shall fail if: | |
| </P> | |
| <DL> | |
| <DT><B>EAGAIN</B> | |
| </DT><DD> | |
| The system lacked the necessary resources (other than memory) to | |
| initialize another read-write lock. | |
| </DD><DT> | |
| <B>ENOMEM</B> | |
| </DT><DD> | |
| Insufficient memory exists to initialize the read-write lock. | |
| </DD><DD STYLE="margin-left: 0cm; margin-bottom: 0.5cm"> | |
| <BR><BR> | |
| </DD></DL> | |
| <P> | |
| The <B>pthread_rwlock_init</B> function may fail if: | |
| </P> | |
| <DL> | |
| <DT><B>EINVAL</B> | |
| </DT><DD STYLE="margin-bottom: 0.5cm"> | |
| The value specified by <I>attr</I> is invalid. | |
| </DD></DL> | |
| <P> | |
| These functions shall not return an error code of [EINTR]. | |
| </P> | |
| <P><I>The following sections are informative.</I> | |
| </P> | |
| <H2><A HREF="#toc5" NAME="sect5">Examples</A></H2> | |
| <P>None. | |
| </P> | |
| <H2><A HREF="#toc6" NAME="sect6">Application Usage</A></H2> | |
| <P>Applications using these and related read-write lock functions may | |
| be subject to priority inversion, as discussed in the Base | |
| Definitions volume of IEEE Std 1003.1-2001, Section 3.285, | |
| Priority Inversion. | |
| </P> | |
| <H2><A HREF="#toc7" NAME="sect7">Rationale</A></H2> | |
| <P>None. | |
| </P> | |
| <H2><A HREF="#toc8" NAME="sect8">Future Directions</A></H2> | |
| <P>None. | |
| </P> | |
| <H2><A HREF="#toc9" NAME="sect9">See Also</A></H2> | |
| <P><A HREF="pthread_rwlock_rdlock.html"><B>pthread_rwlock_rdlock</B>(3)</A> | |
| <B>,</B> <A HREF="pthread_rwlock_timedrdlock.html"><B>pthread_rwlock_timedrdlock</B>(3)</A> | |
| <B>,</B> <A HREF="pthread_rwlock_timedwrlock.html"><B>pthread_rwlock_timedwrlock</B>(3)</A> | |
| <B>,</B> <A HREF="pthread_rwlock_rdlock.html"><B>pthread_rwlock_tryrdlock</B>(3)</A> | |
| <B>,</B> <A HREF="pthread_rwlock_wrlock.html"><B>pthread_rwlock_trywrlock</B>(3)</A> | |
| <B>,</B> <A HREF="pthread_rwlock_unlock.html"><B>pthread_rwlock_unlock</B>(3)</A> | |
| <B>,</B> <A HREF="pthread_rwlock_wrlock.html"><B>pthread_rwlock_wrlock</B>(3)</A> | |
| <B>,</B> the Base Definitions volume of IEEE Std 1003.1-2001, | |
| <I><pthread.h></I> | |
| </P> | |
| <H2><A HREF="#toc10" NAME="sect10">Copyright</A></H2> | |
| <P>Portions of this text are reprinted and reproduced in electronic | |
| form from IEEE Std 1003.1, 2003 Edition, Standard for Information | |
| Technology -- Portable Operating System Interface (POSIX), The Open | |
| Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the | |
| Institute of Electrical and Electronics Engineers, Inc and The Open | |
| Group. 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 <A HREF="http://www.opengroup.org/unix/online.html">http://www.opengroup.org/unix/online.html</A> | |
| . | |
| </P> | |
| <P>Modified by Ross Johnson for use with <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A>.</P> | |
| <HR> | |
| <P><A NAME="toc"></A><B>Table of Contents</B></P> | |
| <UL> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Return | |
| Value</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Errors</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Examples</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect6" NAME="toc6">Application | |
| Usage</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect7" NAME="toc7">Rationale</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect8" NAME="toc8">Future | |
| Directions</A> | |
| </P> | |
| <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect9" NAME="toc9">See | |
| Also</A> | |
| </P> | |
| <LI><P><A HREF="#sect10" NAME="toc10">Copyright</A> | |
| </P> | |
| </UL> | |
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