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| author | Craig Jennings <c@cjennings.net> | 2024-04-07 13:41:34 -0500 |
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| committer | Craig Jennings <c@cjennings.net> | 2024-04-07 13:41:34 -0500 |
| commit | 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 (patch) | |
| tree | f1190704f78f04a2b0b4c977d20fe96a828377f1 /devdocs/elisp/threads.html | |
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diff --git a/devdocs/elisp/threads.html b/devdocs/elisp/threads.html new file mode 100644 index 00000000..0709f40a --- /dev/null +++ b/devdocs/elisp/threads.html @@ -0,0 +1,26 @@ + <h2 class="chapter">Threads</h2> <p>Emacs Lisp provides a limited form of concurrency, called <em>threads</em>. All the threads in a given instance of Emacs share the same memory. Concurrency in Emacs Lisp is “mostly cooperative”, meaning that Emacs will only switch execution between threads at well-defined times. However, the Emacs thread support has been designed in a way to later allow more fine-grained concurrency, and correct programs should not rely on cooperative threading. </p> <p>Currently, thread switching will occur upon explicit request via <code>thread-yield</code>, when waiting for keyboard input or for process output from asynchronous processes (e.g., during <code>accept-process-output</code>), or during blocking operations relating to threads, such as mutex locking or <code>thread-join</code>. </p> <p>Emacs Lisp provides primitives to create and control threads, and also to create and control mutexes and condition variables, useful for thread synchronization. </p> <p>While global variables are shared among all Emacs Lisp threads, local variables are not—a dynamic <code>let</code> binding is local. Each thread also has its own current buffer (see <a href="current-buffer">Current Buffer</a>) and its own match data (see <a href="match-data">Match Data</a>). </p> <p>Note that <code>let</code> bindings are treated specially by the Emacs Lisp implementation. There is no way to duplicate this unwinding and rewinding behavior other than by using <code>let</code>. For example, a manual implementation of <code>let</code> written using <code>unwind-protect</code> cannot arrange for variable values to be thread-specific. </p> <p>In the case of lexical bindings (see <a href="variable-scoping">Variable Scoping</a>), a closure is an object like any other in Emacs Lisp, and bindings in a closure are shared by any threads invoking the closure. </p> <table class="menu" border="0" cellspacing="0"> <tr> +<td align="left" valign="top">• <a href="basic-thread-functions" accesskey="1">Basic Thread Functions</a> +</td> +<td> </td> +<td align="left" valign="top">Basic thread functions. </td> +</tr> <tr> +<td align="left" valign="top">• <a href="mutexes" accesskey="2">Mutexes</a> +</td> +<td> </td> +<td align="left" valign="top">Mutexes allow exclusive access to data. </td> +</tr> <tr> +<td align="left" valign="top">• <a href="condition-variables" accesskey="3">Condition Variables</a> +</td> +<td> </td> +<td align="left" valign="top">Inter-thread events. </td> +</tr> <tr> +<td align="left" valign="top">• <a href="the-thread-list" accesskey="4">The Thread List</a> +</td> +<td> </td> +<td align="left" valign="top">Show the active threads. </td> +</tr> </table><div class="_attribution"> + <p class="_attribution-p"> + Copyright © 1990-1996, 1998-2022 Free Software Foundation, Inc. <br>Licensed under the GNU GPL license.<br> + <a href="https://www.gnu.org/software/emacs/manual/html_node/elisp/Threads.html" class="_attribution-link">https://www.gnu.org/software/emacs/manual/html_node/elisp/Threads.html</a> + </p> +</div> |