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14<h1 align="left">OS_LockMutexFrom[RToW|WToR] <IMG src="../../image/NTR.gif" align="middle"><IMG src="../../image/TWL.gif" align="middle"></h1>
15<h2>Syntax</h2>
16
17<dl>
18  <dd>
19<CODE>#include &lt;nitro/os.h&gt;</CODE><BR> <BR> <CODE>void OS_LockMutexFromRToW( OSMutex* mutex );</CODE><BR> <BR> <CODE>void OS_LockMutexFromWToR( OSMutex* mutex );</CODE></dd>
20</dl>
21
22<h2>Arguments</h2>
23<TABLE border="1" width="100%">
24  <TBODY>
25    <TR>
26      <TD width="13%"><CODE>mutex</CODE></TD>
27      <TD width="87%">Pointer to the <CODE>OSMutex</CODE> structure</TD>
28    </TR>
29  </TBODY>
30</TABLE>
31
32<h2>Return Values</h2>
33<p>None.</p>
34
35<H2>Description</H2>
36<P>Changes the type of the <CODE>mutex</CODE> that is locked.</P>
37<P><CODE>mutex</CODE> is the pointer to the <CODE>OSMutex</CODE> structure to be changed.</P>
38<P>The <CODE>OS_LockMutexFromWToR</CODE> function takes a <CODE>mutex</CODE> that is set to <CODE>write lock</CODE> and changes the setting to <CODE>read lock</CODE>. The <CODE>mutex</CODE> type is then <CODE>read lock</CODE>. To unlock it you need to execute either the <CODE><A href="OS_UnlockMutexRW.html">OS_UnlockMutexR</A></CODE> or <CODE><A href="OS_UnlockMutexRW.html">OS_UnlockMutexRW</A></CODE> function.</P>
39<P>The <CODE>OS_LockMutexFromRToW</CODE> takes a <CODE>mutex</CODE> that is set to <CODE>read lock</CODE> and changes the setting to <CODE>write lock</CODE>. The <CODE>mutex</CODE> type is then <CODE>write lock</CODE>. To unlock it you need to execute either the <CODE><A href="OS_UnlockMutexRW.html">OS_UnlockMutexW</A></CODE> or <CODE><A href="OS_UnlockMutexRW.html">OS_UnlockMutexRW</A></CODE> function.</P>
40<P>Control will not return from either of these functions until the change has succeeded. Internally, the <CODE><A href="OS_TryLockMutexFromToRW.html">OS_TryLockMutexFromWToR</A></CODE> and <CODE><A href="OS_TryLockMutexFromToRW.html">OS_TryLockMutexFromRToW</A></CODE> functions will be called repeatedly until the process succeeds. The process will stop, however, if the function has been specified in a way that cannot succeed. For example, if the <CODE>OS_LockMutexFromToWToR</CODE> function is called to change the mutex from <CODE>write lock</CODE> to <CODE>read lock</CODE> but the mutex is already set to <CODE>read lock</CODE>. (The thread goes to sleep.)</P>
41<h2>See Also</h2>
42<p><CODE><A href="OS_InitMutex.html">OS_InitMutex</A><BR> <A href="OS_LockMutex.html">OS_LockMutex</A><BR> <A href="OS_UnlockMutex.html">OS_UnlockMutex</A></CODE><BR> <CODE><A href="OS_LockMutexRW.html">OS_LockMutexR</A><BR> <A href="OS_LockMutexRW.html">OS_LockMutexW</A><BR> <A href="OS_UnlockMutexRW.html">OS_UnlocMutexR</A><BR> <A href="OS_UnlockMutexRW.html">OS_UnlocMutexW</A><BR> <A href="OS_TryLockMutexRW.html">OS_TryLockMutexR</A><BR> <A href="OS_TryLockMutexRW.html">OS_TryLockMutexW</A><BR> <A href="OS_TryLockMutexFromToRW.html">OS_TryLockMutexFromRToW</A><BR> <A href="OS_TryLockMutexFromToRW.html">OS_TryLockMutexFromWToR</A></CODE></p>
43<H2>Revision History</H2>
44<P>2008/12/17 Initial version.</P>
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