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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_spin_destroy, pthread_spin_init - destroy or initialize a | |
| spin lock object (<B>ADVANCED REALTIME THREADS</B>) | |
| </P> | |
| <H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> | |
| <P><B>#include <pthread.h> </B> | |
| </P> | |
| <P><B>pthread_spinlock_t</B> <I>lock</I> <B>= | |
| PTHREAD_SPINLOCK_INITIALIZER;</B></P> | |
| <P><B>int pthread_spin_destroy(pthread_spinlock_t *</B><I>lock</I><B>); | |
| <BR>int pthread_spin_init(pthread_spinlock_t *</B><I>lock</I><B>, int</B> | |
| <I>pshared</I><B>); </B> | |
| </P> | |
| <H2><A HREF="#toc2" NAME="sect2">Description</A></H2> | |
| <P>The <B>pthread_spin_destroy</B> function shall destroy the spin | |
| lock referenced by <I>lock</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_spin_init</B> . | |
| The results are undefined if <B>pthread_spin_destroy</B> is called | |
| when a thread holds the lock, or if this function is called with an | |
| uninitialized thread spin lock. | |
| </P> | |
| <P>The <B>pthread_spin_init</B> function shall allocate any resources | |
| required to use the spin lock referenced by <I>lock</I> and | |
| initialize the lock to an unlocked state. | |
| </P> | |
| <P><B>Pthreads-w32</B> supports single and multiple processor systems | |
| as well as process CPU affinity masking by checking the mask when the | |
| spin lock is initialized. If the process is using only a single | |
| processor at the time <B>pthread_spin_init</B> is called then the | |
| spin lock is initialized as a PTHREAD_MUTEX_NORMAL mutex object. A | |
| thread that calls <A HREF="pthread_spin_lock.html"><B>pthread_spin_lock(3)</B></A> | |
| will block rather than spin in this case. If the process CPU affinity | |
| mask is altered after the spin lock has been initialised, the spin | |
| lock is not modified, and may no longer be optimal for the number of | |
| CPUs available.</P> | |
| <P><B>Pthreads-w32</B> defines <B>_POSIX_THREAD_PROCESS_SHARED</B> in | |
| pthread.h as -1 to indicate that these routines do not support the | |
| <B>PTHREAD_PROCESS_SHARED</B> attribute. <B>pthread_spin_init</B> | |
| will return the error <B>ENOTSUP</B> if the value of <I>pshared</I> | |
| is not <B>PTHREAD_PROCESS_PRIVATE</B>.</P> | |
| <P>The results are undefined if <B>pthread_spin_init</B> is called | |
| specifying an already initialized spin lock. The results are | |
| undefined if a spin lock is used without first being initialized. | |
| </P> | |
| <P>If the <B>pthread_spin_init</B> function fails, the lock is not | |
| initialized and the contents of <I>lock</I> are undefined. | |
| </P> | |
| <P>Only the object referenced by <I>lock</I> may be used for | |
| performing synchronization. | |
| </P> | |
| <P>The result of referring to copies of that object in calls to | |
| <B>pthread_spin_destroy</B> , <A HREF="pthread_spin_lock.html"><B>pthread_spin_lock</B>(3)</A> | |
| , <A HREF="pthread_spin_lock.html"><B>pthread_spin_trylock</B>(3)</A>, | |
| or <A HREF="pthread_spin_unlock.html"><B>pthread_spin_unlock</B>(3)</A> | |
| is undefined. | |
| </P> | |
| <P><B>Pthreads-w32</B> supports statically initialized spin locks | |
| using <B>PTHREAD_SPINLOCK_INITIALIZER</B>. An application should | |
| still call <B>pthread_spin_destroy</B> at some point to ensure that | |
| any resources consumed by the spin lock are released.</P> | |
| <H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2> | |
| <P>Upon successful completion, these functions 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>These functions may fail if: | |
| </P> | |
| <DL> | |
| <DT><B>EBUSY</B> | |
| </DT><DD> | |
| The implementation has detected an attempt to initialize or destroy | |
| a spin lock while it is in use (for example, while being used in a | |
| <A HREF="pthread_spin_lock.html"><B>pthread_spin_lock</B>(3)</A> | |
| call) by another thread. | |
| </DD><DT> | |
| <B>EINVAL</B> | |
| </DT><DD STYLE="margin-bottom: 0.5cm"> | |
| The value specified by <I>lock</I> is invalid. | |
| </DD></DL> | |
| <P> | |
| The <B>pthread_spin_init</B> function shall fail if: | |
| </P> | |
| <DL> | |
| <DT><B>ENOTSUP</B> | |
| </DT><DD> | |
| The value of <I>pshared</I> is not <B>PTHREAD_PROCESS_PRIVATE</B>.</DD><DT> | |
| <B>ENOMEM</B> | |
| </DT><DD STYLE="margin-bottom: 0.5cm"> | |
| Insufficient memory exists to initialize the lock. | |
| </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>The <B>pthread_spin_destroy</B> and <B>pthread_spin_init</B> | |
| functions are part of the Spin Locks option and need not be provided | |
| on all implementations. | |
| </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_spin_lock.html"><B>pthread_spin_lock</B>(3)</A> <B>,</B> | |
| <A HREF="pthread_spin_unlock.html"><B>pthread_spin_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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