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3.2.1 of GnuTLS.
Copyright (C) 2001-2013 Free Software Foundation, Inc.\\
Copyright (C) 2001-2013 Nikos Mavrogiannopoulos
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<title>GnuTLS 3.2.1: Thread safety</title>
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<a name="Thread-safety"></a>
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Next: <a href="Callback-functions.html#Callback-functions" accesskey="n" rel="next">Callback functions</a>, Previous: <a href="Debugging-and-auditing.html#Debugging-and-auditing" accesskey="p" rel="previous">Debugging and auditing</a>, Up: <a href="Introduction-to-the-library.html#Introduction-to-the-library" accesskey="u" rel="up">Introduction to the library</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Thread-safety-1"></a>
<h4 class="subsection">6.1.5 Thread safety</h4>
<a name="index-thread-safety"></a>
<p>The <acronym>GnuTLS</acronym> library is thread safe by design, meaning that
objects of the library such as TLS sessions, can be safely divided across
threads as long as a single thread accesses a single object. This is
sufficient to support a server which handles several sessions per thread.
If, however, an object needs to be shared across threads then access must be
protected with a mutex. Read-only access to objects, for example the
credentials holding structures, is also thread-safe.
</p>
<p>The random generator of the cryptographic back-end, is not thread safe and requires
mutex locks which are setup by <acronym>GnuTLS</acronym>.
Applications can either call <a href="Core-TLS-API.html#gnutls_005fglobal_005finit">gnutls_global_init</a> which will initialize the default
operating system provided locks (i.e. <code>pthreads</code> on GNU/Linux and
<code>CriticalSection</code> on Windows), or manually specify the locking system using
the function <a href="Core-TLS-API.html#gnutls_005fglobal_005fset_005fmutex">gnutls_global_set_mutex</a> before calling <a href="Core-TLS-API.html#gnutls_005fglobal_005finit">gnutls_global_init</a>.
Setting mutexes manually is recommended
only for applications that have full control of the underlying libraries. If this
is not the case, the use of the operating system defaults is recommended. An example of
non-native thread usage is shown below.
</p>
<div class="example">
<pre class="example">#include <gnutls/gnutls.h>
int main()
{
/* When the system mutexes are not to be used
* gnutls_global_set_mutex() must be called explicitly
*/
gnutls_global_set_mutex (mutex_init, mutex_deinit,
mutex_lock, mutex_unlock);
gnutls_global_init();
}
</pre></div>
<dl>
<dt><a name="index-gnutls_005fglobal_005fset_005fmutex"></a>Function: <em>void</em> <strong>gnutls_global_set_mutex</strong> <em>(mutex_init_func <var>init</var>, mutex_deinit_func <var>deinit</var>, mutex_lock_func <var>lock</var>, mutex_unlock_func <var>unlock</var>)</em></dt>
<dd><p><var>init</var>: mutex initialization function
</p>
<p><var>deinit</var>: mutex deinitialization function
</p>
<p><var>lock</var>: mutex locking function
</p>
<p><var>unlock</var>: mutex unlocking function
</p>
<p>With this function you are allowed to override the default mutex
locks used in some parts of gnutls and dependent libraries. This function
should be used if you have complete control of your program and libraries.
Do not call this function from a library. Instead only initialize gnutls and
the default OS mutex locks will be used.
</p>
<p>This function must be called before <code>gnutls_global_init()</code> .
</p>
<p><strong>Since:</strong> 2.12.0
</p></dd></dl>
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Next: <a href="Callback-functions.html#Callback-functions" accesskey="n" rel="next">Callback functions</a>, Previous: <a href="Debugging-and-auditing.html#Debugging-and-auditing" accesskey="p" rel="previous">Debugging and auditing</a>, Up: <a href="Introduction-to-the-library.html#Introduction-to-the-library" accesskey="u" rel="up">Introduction to the library</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
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