75 lines
3 KiB
HTML
75 lines
3 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Implementation (Linux x86) - SBCL Internals</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="SBCL Internals">
|
||
|
|
<meta name="generator" content="makeinfo 4.11">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="Threads.html#Threads" title="Threads">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
|
||
|
|
This manual is part of the SBCL software system. See the `README'
|
||
|
|
file for more information.
|
||
|
|
|
||
|
|
This manual is in the public domain and is provided with
|
||
|
|
absolutely no warranty. See the `COPYING' and `CREDITS' files for
|
||
|
|
more information.
|
||
|
|
-->
|
||
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
||
|
|
<style type="text/css"><!--
|
||
|
|
pre.display { font-family:inherit }
|
||
|
|
pre.format { font-family:inherit }
|
||
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallexample { font-size:smaller }
|
||
|
|
pre.smalllisp { font-size:smaller }
|
||
|
|
span.sc { font-variant:small-caps }
|
||
|
|
span.roman { font-family:serif; font-weight:normal; }
|
||
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
||
|
|
--></style>
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<div class="node">
|
||
|
|
<p>
|
||
|
|
<a name="Implementation-(Linux-x86)"></a>
|
||
|
|
<a name="Implementation-_0028Linux-x86_0029"></a>
|
||
|
|
Up: <a rel="up" accesskey="u" href="Threads.html#Threads">Threads</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h3 class="section">10.1 Implementation (Linux x86/x86-64)</h3>
|
||
|
|
|
||
|
|
<p>Threading is implemented using pthreads and some Linux specific bits
|
||
|
|
like futexes.
|
||
|
|
|
||
|
|
<p>On x86 the per-thread local bindings for special variables is achieved
|
||
|
|
using the %fs segment register to point to a per-thread storage area.
|
||
|
|
This may cause interesting results if you link to foreign code that
|
||
|
|
expects threading or creates new threads, and the thread library in
|
||
|
|
question uses %fs in an incompatible way. On x86-64 the r12 register
|
||
|
|
has a similar role.
|
||
|
|
|
||
|
|
<p>Queues require the <code>sys_futex</code> system call to be available: this
|
||
|
|
is the reason for the NPTL requirement. We test at runtime that this
|
||
|
|
system call exists.
|
||
|
|
|
||
|
|
<p>Garbage collection is done with the existing Conservative Generational
|
||
|
|
GC. Allocation is done in small (typically 8k) regions: each thread
|
||
|
|
has its own region so this involves no stopping. However, when a
|
||
|
|
region fills, a lock must be obtained while another is allocated, and
|
||
|
|
when a collection is required, all processes are stopped. This is
|
||
|
|
achieved by sending them signals, which may make for interesting
|
||
|
|
behaviour if they are interrupted in system calls. The streams
|
||
|
|
interface is believed to handle the required system call restarting
|
||
|
|
correctly, but this may be a consideration when making other blocking
|
||
|
|
calls e.g. from foreign library code.
|
||
|
|
|
||
|
|
<p>Large amounts of the SBCL library have not been inspected for
|
||
|
|
thread-safety. Some of the obviously unsafe areas have large locks
|
||
|
|
around them, so compilation and fasl loading, for example, cannot be
|
||
|
|
parallelized. Work is ongoing in this area.
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|