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<a href="#define-members">Macros</a> |
<a href="#func-members">Functions</a> </div>
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<div class="title">Mutexes<div class="ingroups"><a class="el" href="group__CMSIS__RTOS__InterThread.html">Inter-Thread Communication and Resource Sharing</a></div></div> </div>
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<p>Synchronize resource access using Mutual Exclusion (Mutex).
<a href="#details">More...</a></p>
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="define-members"></a>
Macros</h2></td></tr>
<tr class="memitem:ga9b522438489d7c402c95332b58bc94f3"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga9b522438489d7c402c95332b58bc94f3">osMutexDef</a>(name)   const <a class="el" href="cmsis__os_8h.html#structosMutexDef__t">osMutexDef_t</a> os_mutex_def_##name = { 0 }</td></tr>
<tr class="memdesc:ga9b522438489d7c402c95332b58bc94f3"><td class="mdescLeft"> </td><td class="mdescRight">Define a Mutex. <a href="#ga9b522438489d7c402c95332b58bc94f3">More...</a><br/></td></tr>
<tr class="separator:ga9b522438489d7c402c95332b58bc94f3"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga1122a86faa64b4a0880c76cf68d0c934"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga1122a86faa64b4a0880c76cf68d0c934">osMutex</a>(name)   &os_mutex_def_##name</td></tr>
<tr class="memdesc:ga1122a86faa64b4a0880c76cf68d0c934"><td class="mdescLeft"> </td><td class="mdescRight">Access a Mutex definition. <a href="#ga1122a86faa64b4a0880c76cf68d0c934">More...</a><br/></td></tr>
<tr class="separator:ga1122a86faa64b4a0880c76cf68d0c934"><td class="memSeparator" colspan="2"> </td></tr>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:ga5c9de56e717016e39e788064e9a291cc"><td class="memItemLeft" align="right" valign="top"><a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a> (const <a class="el" href="cmsis__os_8h.html#structosMutexDef__t">osMutexDef_t</a> *mutex_def)</td></tr>
<tr class="memdesc:ga5c9de56e717016e39e788064e9a291cc"><td class="mdescLeft"> </td><td class="mdescRight">Create and Initialize a Mutex object. <a href="#ga5c9de56e717016e39e788064e9a291cc">More...</a><br/></td></tr>
<tr class="separator:ga5c9de56e717016e39e788064e9a291cc"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga5e1752b73f573ee015dbd9ef1edaba13"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5e1752b73f573ee015dbd9ef1edaba13">osMutexWait</a> (<a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id, uint32_t millisec)</td></tr>
<tr class="memdesc:ga5e1752b73f573ee015dbd9ef1edaba13"><td class="mdescLeft"> </td><td class="mdescRight">Wait until a Mutex becomes available. <a href="#ga5e1752b73f573ee015dbd9ef1edaba13">More...</a><br/></td></tr>
<tr class="separator:ga5e1752b73f573ee015dbd9ef1edaba13"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga006e4744d741e8e132c3d5bbc295afe1"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga006e4744d741e8e132c3d5bbc295afe1">osMutexRelease</a> (<a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id)</td></tr>
<tr class="memdesc:ga006e4744d741e8e132c3d5bbc295afe1"><td class="mdescLeft"> </td><td class="mdescRight">Release a Mutex that was obtained by <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5e1752b73f573ee015dbd9ef1edaba13">osMutexWait</a>. <a href="#ga006e4744d741e8e132c3d5bbc295afe1">More...</a><br/></td></tr>
<tr class="separator:ga006e4744d741e8e132c3d5bbc295afe1"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:gac27e24135185d51d18f3dabc20910219"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#gac27e24135185d51d18f3dabc20910219">osMutexDelete</a> (<a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id)</td></tr>
<tr class="memdesc:gac27e24135185d51d18f3dabc20910219"><td class="mdescLeft"> </td><td class="mdescRight">Delete a Mutex that was created by <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>. <a href="#gac27e24135185d51d18f3dabc20910219">More...</a><br/></td></tr>
<tr class="separator:gac27e24135185d51d18f3dabc20910219"><td class="memSeparator" colspan="2"> </td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Description</h2>
<p><b>Mutual exclusion</b> (widely known as <b>Mutex</b>) is used in various operating systems for resource management. Many resources in a microcontroller device can be used repeatedly, but only by one thread at a time (for example communication channels, memory, and files). Mutexes are used to protect access to a shared resource. A mutex is created and then passed between the threads (they can acquire and release the mutex).</p>
<div class="image">
<img src="Mutex.png" alt="Mutex.png"/>
<div class="caption">
CMSIS-RTOS Mutex</div></div>
<p> A mutex is a special version of a <a class="el" href="group__CMSIS__RTOS__SemaphoreMgmt.html">semaphore</a>. Like the semaphore, it is a container for tokens. But instead of being able to have multiple tokens, a mutex can only carry one (representing the resource). Thus, a mutex token is binary and bounded. The advantage of a mutex is that it introduces thread ownership. When a thread acquires a mutex and becomes its owner, subsequent mutex acquires from that thread will succeed immediately without any latency. Thus, mutex acquires/releases can be nested.</p>
<dl class="section note"><dt>Note</dt><dd><ul>
<li>Mutex management functions cannot be called from interrupt service routines (ISR), unlike a binary semaphore that can be released from an ISR.</li>
<li>CMSIS-RTOS uses <a href="https://en.wikipedia.org/wiki/Reentrant_mutex" target="_blank">reentrant/recursive mutexes</a> only.</li>
</ul>
</dd></dl>
<h2>Working with Mutexes </h2>
<p>To use mutexes, you need to follow these steps for creating and using them:</p>
<ol type="1">
<li>Declare the mutex container and initialize the mutex: <div class="fragment"><div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga9b522438489d7c402c95332b58bc94f3">osMutexDef</a> (uart_mutex); <span class="comment">// Declare mutex</span></div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> (uart_mutex_id); <span class="comment">// Mutex ID</span></div>
</div><!-- fragment --></li>
<li>Create the mutex in a thread: <div class="fragment"><div class="line">uart_mutex_id = <a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>(<a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga1122a86faa64b4a0880c76cf68d0c934">osMutex</a>(uart_mutex));</div>
</div><!-- fragment --></li>
<li>Acquire the mutex when peripheral access is required: <div class="fragment"><div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga5e1752b73f573ee015dbd9ef1edaba13">osMutexWait</a>(uart_mutex_id, <a class="code" href="cmsis__os_8h.html#a9eb9a7a797a42e4b55eb171ecc609ddb">osWaitForever</a>);</div>
</div><!-- fragment --></li>
<li>When finished with the peripheral access, release the mutex: <div class="fragment"><div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga006e4744d741e8e132c3d5bbc295afe1">osMutexRelease</a>(uart_mutex_id);</div>
</div><!-- fragment --> </li>
</ol>
<h2 class="groupheader">Macro Definition Documentation</h2>
<a class="anchor" id="ga1122a86faa64b4a0880c76cf68d0c934"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">#define osMutex</td>
<td>(</td>
<td class="paramtype"> </td>
<td class="paramname">name</td><td>)</td>
<td>   &os_mutex_def_##name</td>
</tr>
</table>
</div><div class="memdoc">
<p>Access to mutex object for the functions <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">name</td><td>name of the mutex object. </td></tr>
</table>
</dd>
</dl>
<dl class="section note"><dt>Note</dt><dd>CAN BE CHANGED: The parameter to <b>osMutex</b> shall be consistent but the macro body is implementation specific in every CMSIS-RTOS. </dd></dl>
</div>
</div>
<a class="anchor" id="ga9b522438489d7c402c95332b58bc94f3"></a>
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<div class="memproto">
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<td class="memname">#define osMutexDef</td>
<td>(</td>
<td class="paramtype"> </td>
<td class="paramname">name</td><td>)</td>
<td>   const <a class="el" href="cmsis__os_8h.html#structosMutexDef__t">osMutexDef_t</a> os_mutex_def_##name = { 0 }</td>
</tr>
</table>
</div><div class="memdoc">
<p>Define a mutex object that is referenced by <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga1122a86faa64b4a0880c76cf68d0c934">osMutex</a>.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">name</td><td>name of the mutex object. </td></tr>
</table>
</dd>
</dl>
<dl class="section note"><dt>Note</dt><dd>CAN BE CHANGED: The parameter to <b>osMutexDef</b> shall be consistent but the macro body is implementation specific in every CMSIS-RTOS. </dd></dl>
</div>
</div>
<h2 class="groupheader">Function Documentation</h2>
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<td class="memname"><a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> osMutexCreate </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="cmsis__os_8h.html#structosMutexDef__t">osMutexDef_t</a> * </td>
<td class="paramname"><em>mutex_def</em></td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">mutex_def</td><td>mutex definition referenced with <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga1122a86faa64b4a0880c76cf68d0c934">osMutex</a>. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>mutex ID for reference by other functions or NULL in case of error. </dd></dl>
<dl class="section note"><dt>Note</dt><dd>MUST REMAIN UNCHANGED: <b>osMutexCreate</b> shall be consistent in every CMSIS-RTOS.</dd></dl>
<p>Create and initialize a Mutex object.</p>
<dl class="section note"><dt>Note</dt><dd>Cannot be called from <a class="el" href="functionOverview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>.</dd></dl>
<p><b>Code Example</b> </p>
<div class="fragment"><div class="line"><span class="preprocessor">#include "<a class="code" href="cmsis__os_8h.html">cmsis_os.h</a>"</span></div>
<div class="line"> </div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga9b522438489d7c402c95332b58bc94f3">osMutexDef</a> (MutexIsr); <span class="comment">// Mutex name definition</span></div>
<div class="line"> </div>
<div class="line"><span class="keywordtype">void</span> CreateMutex (<span class="keywordtype">void</span>) {</div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id; </div>
<div class="line"> </div>
<div class="line"> mutex_id = <a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a> (<a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga1122a86faa64b4a0880c76cf68d0c934">osMutex</a> (MutexIsr));</div>
<div class="line"> <span class="keywordflow">if</span> (mutex_id != NULL) {</div>
<div class="line"> <span class="comment">// Mutex object created</span></div>
<div class="line"> } </div>
<div class="line">}</div>
</div><!-- fragment -->
</div>
</div>
<a class="anchor" id="gac27e24135185d51d18f3dabc20910219"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> osMutexDelete </td>
<td>(</td>
<td class="paramtype"><a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> </td>
<td class="paramname"><em>mutex_id</em></td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">mutex_id</td><td>mutex ID obtained by <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>status code that indicates the execution status of the function. </dd></dl>
<dl class="section note"><dt>Note</dt><dd>MUST REMAIN UNCHANGED: <b>osMutexDelete</b> shall be consistent in every CMSIS-RTOS.</dd></dl>
<p>Delete a Mutex object. The function releases internal memory obtained for Mutex handling. After this call the <em>mutex_id</em> is no longer valid and cannot be used. The Mutex may be created again using the function <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>.</p>
<p><b><a class="el" href="group__CMSIS__RTOS__Status.html">Status and Error Codes</a></b><br/>
</p>
<ul>
<li><em>osOK:</em> the mutex object has been deleted.</li>
<li><em>osErrorISR:</em> <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#gac27e24135185d51d18f3dabc20910219">osMutexDelete</a> cannot be called from interrupt service routines.</li>
<li><em>osErrorResource:</em> all tokens have already been released.</li>
<li><em>osErrorParameter:</em> the parameter <em>mutex_id</em> is incorrect.</li>
</ul>
<dl class="section note"><dt>Note</dt><dd>Cannot be called from <a class="el" href="functionOverview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>.</dd></dl>
<p><b>Code Example</b> </p>
<div class="fragment"><div class="line"><span class="preprocessor">#include "<a class="code" href="cmsis__os_8h.html">cmsis_os.h</a>"</span></div>
<div class="line"> </div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga9b522438489d7c402c95332b58bc94f3">osMutexDef</a> (MutexIsr); <span class="comment">// Mutex name definition </span></div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id; <span class="comment">// Mutex id populated by the function CreateMutex()</span></div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> CreateMutex (<span class="keywordtype">void</span>); <span class="comment">// function prototype that creates the Mutex</span></div>
<div class="line"> </div>
<div class="line"><span class="keywordtype">void</span> DeleteMutex (<a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id) {</div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> status;</div>
<div class="line"> </div>
<div class="line"> <span class="keywordflow">if</span> (mutex_id != NULL) {</div>
<div class="line"> status = <a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#gac27e24135185d51d18f3dabc20910219">osMutexDelete</a>(mutex_id);</div>
<div class="line"> <span class="keywordflow">if</span> (status != <a class="code" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99ea9e1c9e2550bb4de8969a935acffc968f">osOK</a>) {</div>
<div class="line"> <span class="comment">// handle failure code</span></div>
<div class="line"> }</div>
<div class="line"> }</div>
<div class="line">}</div>
</div><!-- fragment -->
</div>
</div>
<a class="anchor" id="ga006e4744d741e8e132c3d5bbc295afe1"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> osMutexRelease </td>
<td>(</td>
<td class="paramtype"><a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> </td>
<td class="paramname"><em>mutex_id</em></td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">mutex_id</td><td>mutex ID obtained by <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>status code that indicates the execution status of the function. </dd></dl>
<dl class="section note"><dt>Note</dt><dd>MUST REMAIN UNCHANGED: <b>osMutexRelease</b> shall be consistent in every CMSIS-RTOS.</dd></dl>
<p>Release a Mutex that was obtained with <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5e1752b73f573ee015dbd9ef1edaba13">osMutexWait</a>. Other threads that currently wait for the same mutex will be now put into the state <b>READY</b>.</p>
<p><b><a class="el" href="group__CMSIS__RTOS__Status.html">Status and Error Codes</a></b><br/>
</p>
<ul>
<li><em>osOK:</em> the mutex has been correctly released.</li>
<li><em>osErrorResource:</em> the mutex was not obtained before.</li>
<li><em>osErrorParameter:</em> the parameter <em>mutex_id</em> is incorrect.</li>
<li><em>osErrorISR:</em> <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga006e4744d741e8e132c3d5bbc295afe1">osMutexRelease</a> cannot be called from interrupt service routines.</li>
</ul>
<dl class="section note"><dt>Note</dt><dd>Cannot be called from <a class="el" href="functionOverview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>.</dd></dl>
<p><b>Code Example</b> </p>
<div class="fragment"><div class="line"><span class="preprocessor">#include "<a class="code" href="cmsis__os_8h.html">cmsis_os.h</a>"</span></div>
<div class="line"> </div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga9b522438489d7c402c95332b58bc94f3">osMutexDef</a> (MutexIsr); <span class="comment">// Mutex name definition </span></div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id; <span class="comment">// Mutex id populated by the function CreateMutex()</span></div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> CreateMutex (<span class="keywordtype">void</span>); <span class="comment">// function prototype that creates the Mutex</span></div>
<div class="line"> </div>
<div class="line"><span class="keywordtype">void</span> ReleaseMutex (<a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id) {</div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> status;</div>
<div class="line"> </div>
<div class="line"> <span class="keywordflow">if</span> (mutex_id != NULL) {</div>
<div class="line"> status = <a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga006e4744d741e8e132c3d5bbc295afe1">osMutexRelease</a>(mutex_id);</div>
<div class="line"> <span class="keywordflow">if</span> (status != <a class="code" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99ea9e1c9e2550bb4de8969a935acffc968f">osOK</a>) {</div>
<div class="line"> <span class="comment">// handle failure code</span></div>
<div class="line"> }</div>
<div class="line"> }</div>
<div class="line">}</div>
</div><!-- fragment -->
</div>
</div>
<a class="anchor" id="ga5e1752b73f573ee015dbd9ef1edaba13"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> osMutexWait </td>
<td>(</td>
<td class="paramtype"><a class="el" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> </td>
<td class="paramname"><em>mutex_id</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>millisec</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">mutex_id</td><td>mutex ID obtained by <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a>. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">millisec</td><td><a class="el" href="functionOverview.html#CMSIS_RTOS_TimeOutValue">Timout Value</a> or 0 in case of no time-out. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>status code that indicates the execution status of the function. </dd></dl>
<dl class="section note"><dt>Note</dt><dd>MUST REMAIN UNCHANGED: <b>osMutexWait</b> shall be consistent in every CMSIS-RTOS.</dd></dl>
<p>Wait until a Mutex becomes available. If no other thread has obtained the Mutex, the function instantly returns and blocks the mutex object.</p>
<p>The argument <em>millisec</em> specifies how long the system waits for a mutex. While the system waits the thread that is calling this function is put into the state <b>WAITING</b>. The <em>millisec</em> timeout can have the following values:</p>
<ul>
<li>when <em>millisec</em> is 0, the function returns instantly.</li>
<li>when <em>millisec</em> is set to <b>osWaitForever</b> the function will wait for an infinite time until the mutex becomes available.</li>
<li>all other values specify a time in millisecond for a timeout.</li>
</ul>
<p><b><a class="el" href="group__CMSIS__RTOS__Status.html">Status and Error Codes</a></b><br/>
</p>
<ul>
<li><em>osOK:</em> the mutex has been obtained.</li>
<li><em>osErrorTimeoutResource:</em> the mutex could not be obtained in the given time.</li>
<li><em>osErrorResource:</em> the mutex could not be obtained when no timeout was specified.</li>
<li><em>osErrorParameter:</em> the parameter <em>mutex_id</em> is incorrect.</li>
<li><em>osErrorISR:</em> <a class="el" href="group__CMSIS__RTOS__MutexMgmt.html#ga5e1752b73f573ee015dbd9ef1edaba13">osMutexWait</a> cannot be called from interrupt service routines.</li>
</ul>
<dl class="section note"><dt>Note</dt><dd>Cannot be called from <a class="el" href="functionOverview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>.</dd></dl>
<p><b>Code Example</b> </p>
<div class="fragment"><div class="line"><span class="preprocessor">#include "<a class="code" href="cmsis__os_8h.html">cmsis_os.h</a>"</span></div>
<div class="line"> </div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga9b522438489d7c402c95332b58bc94f3">osMutexDef</a> (MutexIsr);</div>
<div class="line"> </div>
<div class="line"><span class="keywordtype">void</span> WaitMutex (<span class="keywordtype">void</span>) {</div>
<div class="line"><a class="code" href="cmsis__os_8h.html#a3263c1ad9fd79b84f908d65e8da44ac2">osMutexId</a> mutex_id; </div>
<div class="line"><a class="code" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> status;</div>
<div class="line"> </div>
<div class="line"> mutex_id = <a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga5c9de56e717016e39e788064e9a291cc">osMutexCreate</a> (<a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga1122a86faa64b4a0880c76cf68d0c934">osMutex</a> (MutexIsr));</div>
<div class="line"> <span class="keywordflow">if</span> (mutex_id != NULL) {</div>
<div class="line"> status = <a class="code" href="group__CMSIS__RTOS__MutexMgmt.html#ga5e1752b73f573ee015dbd9ef1edaba13">osMutexWait</a> (mutex_id, 0);</div>
<div class="line"> <span class="keywordflow">if</span> (status != <a class="code" href="group__CMSIS__RTOS__Status.html#gae2e091fefc4c767117727bd5aba4d99ea9e1c9e2550bb4de8969a935acffc968f">osOK</a>) {</div>
<div class="line"> <span class="comment">// handle failure code</span></div>
<div class="line"> }</div>
<div class="line"> }</div>
<div class="line">}</div>
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