<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/> <meta http-equiv="X-UA-Compatible" content="IE=9"/> <title>Mutexes</title> <title>CMSIS-RTOS: Mutexes</title> <link href="tabs.css" rel="stylesheet" type="text/css"/> <link href="cmsis.css" rel="stylesheet" type="text/css" /> <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript" src="dynsections.js"></script> <script type="text/javascript" src="printComponentTabs.js"></script> <link href="navtree.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="resize.js"></script> <script type="text/javascript" src="navtree.js"></script> <script type="text/javascript"> $(document).ready(initResizable); $(window).load(resizeHeight); </script> <link href="search/search.css" rel="stylesheet" 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class="SelectionMark"> </span>Pages</a></div> <!-- iframe showing the search results (closed by default) --> <div id="MSearchResultsWindow"> <iframe src="javascript:void(0)" frameborder="0" name="MSearchResults" id="MSearchResults"> </iframe> </div> <div class="header"> <div class="summary"> <a href="#define-members">Macros</a> | <a href="#func-members">Functions</a> </div> <div class="headertitle"> <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> </div><!--header--> <div class="contents"> <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="structosMutexDef__t.html">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> </table><table class="memberdecls"> <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="structosMutexDef__t.html">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> </table> <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> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <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="structosMutexDef__t.html">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> <a class="anchor" id="ga5c9de56e717016e39e788064e9a291cc"></a> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <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="structosMutexDef__t.html">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> </div><!-- fragment --> </div> </div> </div><!-- contents --> </div><!-- doc-content --> <!-- start footer part --> <div id="nav-path" class="navpath"><!-- id is needed for treeview function! --> <ul> <li class="footer">Generated on Wed Feb 8 2017 10:21:02 for CMSIS-RTOS by ARM Ltd. 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