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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_trywrlock, pthread_rwlock_wrlock - lock a | |
| read-write lock object for writing | |
| </P> | |
| <H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> | |
| <P><B>#include <pthread.h> </B> | |
| </P> | |
| <P><B>int pthread_rwlock_trywrlock(pthread_rwlock_t <I>*</I></B><I>rwlock</I><B>); | |
| <BR>int pthread_rwlock_wrlock(pthread_rwlock_t <I>*</I></B><I>rwlock</I><B>); | |
| </B> | |
| </P> | |
| <H2><A HREF="#toc2" NAME="sect2">Description</A></H2> | |
| <P>The <B>pthread_rwlock_trywrlock</B> function shall apply a write | |
| lock like the <B>pthread_rwlock_wrlock</B> function, with the | |
| exception that the function shall fail if any thread currently holds | |
| <I>rwlock</I> (for reading or writing). | |
| </P> | |
| <P>The <B>pthread_rwlock_wrlock</B> function shall apply a write lock | |
| to the read-write lock referenced by <I>rwlock</I>. The calling | |
| thread acquires the write lock if no other thread (reader or writer) | |
| holds the read-write lock <I>rwlock</I>. Otherwise, the thread shall | |
| block until it can acquire the lock. The calling thread may deadlock | |
| if at the time the call is made it holds the read-write lock (whether | |
| a read or write lock). | |
| </P> | |
| <P><B>Pthreads-win32</B> does not prefer either writers or readers in | |
| acquiring the lock – all threads enter a single prioritised FIFO | |
| queue. While this may not be optimally efficient for some | |
| applications, it does ensure that one type does not starve the other.</P> | |
| <P>Results are undefined if any of these functions are called with an | |
| uninitialized read-write lock. | |
| </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>The <B>pthread_rwlock_trywrlock</B> function shall return zero if | |
| the lock for writing on the read-write lock object referenced by | |
| <I>rwlock</I> is acquired. Otherwise, an error number shall be | |
| returned to indicate the error. | |
| </P> | |
| <P>If successful, the <B>pthread_rwlock_wrlock</B> function shall | |
| return zero; otherwise, an error number shall be returned to indicate | |
| the error. | |
| </P> | |
| <H2><A HREF="#toc4" NAME="sect4">Errors</A></H2> | |
| <P>The <B>pthread_rwlock_trywrlock</B> function shall fail if: | |
| </P> | |
| <DL> | |
| <DT><B>EBUSY</B> | |
| </DT><DD STYLE="margin-bottom: 0.5cm"> | |
| The read-write lock could not be acquired for writing because it was | |
| already locked for reading or writing. | |
| </DD></DL> | |
| <P> | |
| The <B>pthread_rwlock_trywrlock</B> and <B>pthread_rwlock_wrlock</B> | |
| functions may fail if: | |
| </P> | |
| <DL> | |
| <DT><B>EINVAL</B> | |
| </DT><DD STYLE="margin-bottom: 0.5cm"> | |
| The value specified by <I>rwlock</I> does not refer to an | |
| initialized read-write lock object. | |
| </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 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_init.html"><B>pthread_rwlock_destroy</B>(3)</A> | |
| <B>,</B> <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_unlock.html"><B>pthread_rwlock_unlock</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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