141 lines
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141 lines
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<TITLE>"PTHREAD_SPIN_LOCK"(P) manual page</TITLE>
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<H4>POSIX Threads for Windows – REFERENCE - <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A></H4>
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<P><A HREF="index.html">Reference Index</A></P>
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<P><A HREF="#toc">Table of Contents</A></P>
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<H2><A HREF="#toc0" NAME="sect0">Name</A></H2>
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<P>pthread_spin_lock, pthread_spin_trylock - lock a spin lock object
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(<B>ADVANCED REALTIME THREADS</B>)
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</P>
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<H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2>
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<P><B>#include <pthread.h> </B>
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</P>
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<P><B>int pthread_spin_lock(pthread_spinlock_t *</B><I>lock</I><B>);
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<BR>int pthread_spin_trylock(pthread_spinlock_t *</B><I>lock</I><B>);
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</B>
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</P>
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<H2><A HREF="#toc2" NAME="sect2">Description</A></H2>
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<P>The <B>pthread_spin_lock</B> function shall lock the spin lock
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referenced by <I>lock</I>. The calling thread shall acquire the lock
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if it is not held by another thread. Otherwise, the thread shall spin
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(that is, shall not return from the <B>pthread_spin_lock</B> call)
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until the lock becomes available. The results are undefined if the
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calling thread holds the lock at the time the call is made.</P>
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<P><B>Pthreads-w32</B> supports single and multiple processor systems
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as well as process CPU affinity masking by checking the mask when the
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spin lock is initialized. If the process is using only a single
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processor at the time <A HREF="pthread_spin_init.html"><B>pthread_spin_init</B>(3)</A>
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is called then the spin lock is initialized as a PTHREAD_MUTEX_NORMAL
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mutex object. A thread that calls <B>pthread_spin_lock</B> will block
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rather than spin in this case. If the process CPU affinity mask is
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altered after the spin lock has been initialised, the spin lock is
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not modified, and may no longer be optimal for the number of CPUs
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available.</P>
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<P>The <B>pthread_spin_trylock</B> function shall lock the spin lock
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referenced by <I>lock</I> if it is not held by any thread. Otherwise,
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the function shall fail.
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</P>
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<P>The results are undefined if any of these functions is called with
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an uninitialized spin lock.
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</P>
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<H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2>
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<P>Upon successful completion, these functions shall return zero;
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otherwise, an error number shall be returned to indicate the error.
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</P>
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<H2><A HREF="#toc4" NAME="sect4">Errors</A></H2>
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<P>These functions may fail if:
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</P>
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<DL>
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<DT><B>EINVAL</B>
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</DT><DD STYLE="margin-bottom: 0.5cm">
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The value specified by <I>lock</I> does not refer to an initialized
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spin lock object.
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</DD></DL>
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<P>
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The <B>pthread_spin_trylock</B> function shall fail if:
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</P>
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<DL>
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<DT><B>EBUSY</B>
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</DT><DD STYLE="margin-bottom: 0.5cm">
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A thread currently holds the lock.
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</DD></DL>
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<P>
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These functions shall not return an error code of [EINTR].
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</P>
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<P><I>The following sections are informative.</I>
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</P>
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<H2><A HREF="#toc5" NAME="sect5">Examples</A></H2>
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<P>None.
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</P>
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<H2><A HREF="#toc6" NAME="sect6">Application Usage</A></H2>
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<P>Applications using this function may be subject to priority
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inversion, as discussed in the Base Definitions volume of
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IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.
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</P>
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<H2><A HREF="#toc7" NAME="sect7">Rationale</A></H2>
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<P>None.
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</P>
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<H2><A HREF="#toc8" NAME="sect8">Future Directions</A></H2>
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<P>None.
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</P>
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<H2><A HREF="#toc9" NAME="sect9">See Also</A></H2>
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<P><A HREF="pthread_spin_init.html"><B>pthread_spin_destroy</B>(3)</A>
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<B>,</B> <A HREF="pthread_spin_unlock.html"><B>pthread_spin_unlock</B>(3)</A>
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<B>,</B> the Base Definitions volume of IEEE Std 1003.1-2001,
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<I><pthread.h></I>
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</P>
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<H2><A HREF="#toc10" NAME="sect10">Copyright</A></H2>
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<P>Portions of this text are reprinted and reproduced in electronic
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form from IEEE Std 1003.1, 2003 Edition, Standard for Information
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Technology -- Portable Operating System Interface (POSIX), The Open
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Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the
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Institute of Electrical and Electronics Engineers, Inc and The Open
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Group. In the event of any discrepancy between this version and the
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original IEEE and The Open Group Standard, the original IEEE and The
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Open Group Standard is the referee document. The original Standard
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can be obtained online at <A HREF="http://www.opengroup.org/unix/online.html">http://www.opengroup.org/unix/online.html</A>
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.
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</P>
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<P>Modified by Ross Johnson for use with <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A>.</P>
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<HR>
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<P><A NAME="toc"></A><B>Table of Contents</B></P>
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<UL>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Return
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Value</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Errors</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Examples</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect6" NAME="toc6">Application
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Usage</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect7" NAME="toc7">Rationale</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect8" NAME="toc8">Future
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Directions</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect9" NAME="toc9">See
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Also</A>
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</P>
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<LI><P><A HREF="#sect10" NAME="toc10">Copyright</A>
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</P>
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</UL>
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