<!--$Id: mutex_alloc.so,v 10.3 2007/09/21 20:06:03 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: DbEnv::mutex_alloc</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td> <b>DbEnv::mutex_alloc</b> </td> <td align=right> <a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a> <a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td> </tr></table> <hr size=1 noshade> <tt> <b><pre> #include <db_cxx.h> <p> int DbEnv::mutex_alloc(u_int32_t flags, db_mutex_t *mutexp); </pre></b> <hr size=1 noshade> <b>Description: DbEnv::mutex_alloc</b> <p>The DbEnv::mutex_alloc method allocates a mutex and returns a reference to it into the memory specified by <b>mutexp</b>.</p> <p>The DbEnv::mutex_alloc method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is called.</p> <p>The DbEnv::mutex_alloc method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </p> <b>Parameters</b> <br> <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or the following value: <br> <b><a name="DB_MUTEX_PROCESS_ONLY">DB_MUTEX_PROCESS_ONLY</a></b><ul compact><li>The mutex is associated with a single process. The <a href="../api_cxx/env_failchk.html">DbEnv::failchk</a> method will release mutexes held by any process which has exited.</ul> <b><a name="DB_MUTEX_SELF_BLOCK">DB_MUTEX_SELF_BLOCK</a></b><ul compact><li>The mutex must be self-blocking. That is, if a thread of control locks the mutex and then attempts to lock the mutex again, the thread of control will block until another thread of control releases the original lock on the mutex, allowing the original thread of control to lock the mutex the second time. Attempting to re-acquire a mutex for which the DB_MUTEX_SELF_BLOCK flag was not specified will result in undefined behavior.</ul> <br></ul> <b>mutexp</b><ul compact><li>The <b>mutexp</b> parameter references memory into which the mutex reference is copied.</ul> <br> <br><b>Errors</b> <p>The DbEnv::mutex_alloc method may fail and throw <a href="../api_cxx/except_class.html">DbException</a>, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:</p> <br> <b>EINVAL</b><ul compact><li>An invalid flag value or parameter was specified.</ul> <br> <hr size=1 noshade> <br><b>Class</b> <a href="../api_cxx/env_class.html">DbEnv</a> <br><b>See Also</b> <a href="../api_cxx/env_list.html">Database Environments and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>