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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
| commit | c0b7206652b2852bc574694e7ba07ba1c2acdc00 (patch) | |
| tree | 5cb95cb0e19e03610525903df46279df2c3b7eb1 /rubbos/app/httpd-2.0.64/docs/manual/developer/thread_safety.html.en | |
| parent | b6d3d6e668b793220f2d3af1bc3e828553dc3fe6 (diff) | |
delete app
Change-Id: Id4c572809969ebe89e946e88063eaed262cff3f2
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/httpd-2.0.64/docs/manual/developer/thread_safety.html.en')
| -rw-r--r-- | rubbos/app/httpd-2.0.64/docs/manual/developer/thread_safety.html.en | 285 |
1 files changed, 0 insertions, 285 deletions
diff --git a/rubbos/app/httpd-2.0.64/docs/manual/developer/thread_safety.html.en b/rubbos/app/httpd-2.0.64/docs/manual/developer/thread_safety.html.en deleted file mode 100644 index 82b4e5a7..00000000 --- a/rubbos/app/httpd-2.0.64/docs/manual/developer/thread_safety.html.en +++ /dev/null @@ -1,285 +0,0 @@ -<?xml version="1.0" encoding="ISO-8859-1"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> -<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- - XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX - This file is generated from xml source: DO NOT EDIT - XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX - --> -<title>Apache 2.0 Thread Safety Issues - Apache HTTP Server</title> -<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> -<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> -<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /> -<link href="../images/favicon.ico" rel="shortcut icon" /></head> -<body id="manual-page"><div id="page-header"> -<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> -<p class="apache">Apache HTTP Server Version 2.0</p> -<img alt="" src="../images/feather.gif" /></div> -<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> -<div id="path"> -<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Developer Documentation</a></div><div id="page-content"><div id="preamble"><h1>Apache 2.0 Thread Safety Issues</h1> -<div class="toplang"> -<p><span>Available Languages: </span><a href="../en/developer/thread_safety.html" title="English"> en </a></p> -</div> - - <p>When using any of the threaded mpms in Apache 2.0 it is important - that every function called from Apache be thread safe. When linking in 3rd - party extensions it can be difficult to determine whether the resulting - server will be thread safe. Casual testing generally won't tell you this - either as thread safety problems can lead to subtle race conditons that - may only show up in certain conditions under heavy load.</p> -</div> -<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#variables">Global and static variables</a></li> -<li><img alt="" src="../images/down.gif" /> <a href="#errno">errno</a></li> -<li><img alt="" src="../images/down.gif" /> <a href="#functions">Common standard troublesome functions</a></li> -<li><img alt="" src="../images/down.gif" /> <a href="#commonlibs">Common 3rd Party Libraries</a></li> -<li><img alt="" src="../images/down.gif" /> <a href="#liblist">Library List</a></li> -</ul></div> -<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> -<div class="section"> -<h2><a name="variables" id="variables">Global and static variables</a></h2> - <p>When writing your module or when trying to determine if a module or - 3rd party library is thread safe there are some common things to keep in - mind.</p> - - <p>First, you need to recognize that in a threaded model each individual - thread has its own program counter, stack and registers. Local variables - live on the stack, so those are fine. You need to watch out for any - static or global variables. This doesn't mean that you are absolutely not - allowed to use static or global variables. There are times when you - actually want something to affect all threads, but generally you need to - avoid using them if you want your code to be thread safe.</p> - - <p>In the case where you have a global variable that needs to be global and - accessed by all threads, be very careful when you update it. If, for - example, it is an incrementing counter, you need to atomically increment - it to avoid race conditions with other threads. You do this using a mutex - (mutual exclusion). Lock the mutex, read the current value, increment it - and write it back and then unlock the mutex. Any other thread that wants - to modify the value has to first check the mutex and block until it is - cleared.</p> - - <p>If you are using <a href="http://apr.apache.org/">APR</a>, have a look - at the <code>apr_atomic_<var>*</var></code> functions and the - <code>apr_thread_mutex_<var>*</var></code> functions.</p> - -</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> -<div class="section"> -<h2><a name="errno" id="errno">errno</a></h2> - <p>This is a common global variable that holds the error number of the - last error that occurred. If one thread calls a low-level function that - sets errno and then another thread checks it, we are bleeding error - numbers from one thread into another. To solve this, make sure your - module or library defines <code>_REENTRANT</code> or is compiled with - <code>-D_REENTRANT</code>. This will make errno a per-thread variable - and should hopefully be transparent to the code. It does this by doing - something like this:</p> - - <div class="example"><p><code> - #define errno (*(__errno_location())) - </code></p></div> - - <p>which means that accessing errno will call - <code>__errno_location()</code> which is provided by the libc. Setting - <code>_REENTRANT</code> also forces redefinition of some other functions - to their <code><var>*</var>_r</code> equivalents and sometimes changes - the common <code>getc</code>/<code>putc</code> macros into safer function - calls. Check your libc documentation for specifics. Instead of, or in - addition to <code>_REENTRANT</code> the symbols that may affect this are - <code>_POSIX_C_SOURCE</code>, <code>_THREAD_SAFE</code>, - <code>_SVID_SOURCE</code>, and <code>_BSD_SOURCE</code>.</p> -</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> -<div class="section"> -<h2><a name="functions" id="functions">Common standard troublesome functions</a></h2> - <p>Not only do things have to be thread safe, but they also have to be - reentrant. <code>strtok()</code> is an obvious one. You call it the first - time with your delimiter which it then remembers and on each subsequent - call it returns the next token. Obviously if multiple threads are - calling it you will have a problem. Most systems have a reentrant version - of of the function called <code>strtok_r()</code> where you pass in an - extra argument which contains an allocated <code>char *</code> which the - function will use instead of its own static storage for maintaining - the tokenizing state. If you are using <a href="http://apr.apache.org/">APR</a> you can use <code>apr_strtok()</code>.</p> - - <p><code>crypt()</code> is another function that tends to not be reentrant, - so if you run across calls to that function in a library, watch out. On - some systems it is reentrant though, so it is not always a problem. If - your system has <code>crypt_r()</code> chances are you should be using - that, or if possible simply avoid the whole mess by using md5 instead.</p> - -</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> -<div class="section"> -<h2><a name="commonlibs" id="commonlibs">Common 3rd Party Libraries</a></h2> - <p>The following is a list of common libraries that are used by 3rd party - Apache modules. You can check to see if your module is using a potentially - unsafe library by using tools such as <code>ldd(1)</code> and - <code>nm(1)</code>. For <a href="http://www.php.net/">PHP</a>, for example, - try this:</p> - - <div class="example"><p><code> - % ldd libphp4.so<br /> - libsablot.so.0 => /usr/local/lib/libsablot.so.0 (0x401f6000)<br /> - libexpat.so.0 => /usr/lib/libexpat.so.0 (0x402da000)<br /> - libsnmp.so.0 => /usr/lib/libsnmp.so.0 (0x402f9000)<br /> - libpdf.so.1 => /usr/local/lib/libpdf.so.1 (0x40353000)<br /> - libz.so.1 => /usr/lib/libz.so.1 (0x403e2000)<br /> - libpng.so.2 => /usr/lib/libpng.so.2 (0x403f0000)<br /> - libmysqlclient.so.11 => /usr/lib/libmysqlclient.so.11 (0x40411000)<br /> - libming.so => /usr/lib/libming.so (0x40449000)<br /> - libm.so.6 => /lib/libm.so.6 (0x40487000)<br /> - libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0x404a8000)<br /> - libjpeg.so.62 => /usr/lib/libjpeg.so.62 (0x404e7000)<br /> - libcrypt.so.1 => /lib/libcrypt.so.1 (0x40505000)<br /> - libssl.so.2 => /lib/libssl.so.2 (0x40532000)<br /> - libcrypto.so.2 => /lib/libcrypto.so.2 (0x40560000)<br /> - libresolv.so.2 => /lib/libresolv.so.2 (0x40624000)<br /> - libdl.so.2 => /lib/libdl.so.2 (0x40634000)<br /> - libnsl.so.1 => /lib/libnsl.so.1 (0x40637000)<br /> - libc.so.6 => /lib/libc.so.6 (0x4064b000)<br /> - /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x80000000) - </code></p></div> - - <p>In addition to these libraries you will need to have a look at any - libraries linked statically into the module. You can use <code>nm(1)</code> - to look for individual symbols in the module.</p> -</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> -<div class="section"> -<h2><a name="liblist" id="liblist">Library List</a></h2> - <p>Please drop a note to <a href="http://httpd.apache.org/lists.html#http-dev">dev@httpd.apache.org</a> - if you have additions or corrections to this list.</p> - - <table class="bordered"><tr class="header"><th>Library</th><th>Version</th><th>Thread Safe?</th><th>Notes</th></tr> -<tr><td><a href="http://aspell.sourceforge.net/">ASpell/PSpell</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://www.sleepycat.com/">Berkeley DB</a></td> - <td>3.x, 4.x</td> - <td>Yes</td> - <td>Be careful about sharing a connection across threads.</td></tr> -<tr><td><a href="http://sources.redhat.com/bzip2/index.html">bzip2</a></td> - <td> </td> - <td>Yes</td> - <td>Both low-level and high-level APIs are thread-safe. However, - high-level API requires thread-safe access to errno.</td></tr> -<tr class="odd"><td><a href="http://cr.yp.to/cdb.html">cdb</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://www.washington.edu/imap/">C-Client</a></td> - <td> </td> - <td>Perhaps</td> - <td>c-client uses <code>strtok()</code> and - <code>gethostbyname()</code> which are not thread-safe on most C - library implementations. c-client's static data is meant to be shared - across threads. If <code>strtok()</code> and - <code>gethostbyname()</code> are thread-safe on your OS, c-client - <em>may</em> be thread-safe.</td></tr> -<tr class="odd"><td><a href="http://www.fastio.com/">cpdflib</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://www.ijg.org/files/">libcrypt</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://expat.sourceforge.net/">Expat</a></td> - <td> </td> - <td>Yes</td> - <td>Need a separate parser instance per thread</td></tr> -<tr><td><a href="http://www.freetds.org/">FreeTDS</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://www.freetype.org/">FreeType</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://www.boutell.com/gd/">GD 1.8.x</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://www.boutell.com/gd/">GD 2.0.x</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://www.gnu.org/software/gdbm/gdbm.html">gdbm</a></td> - <td> </td> - <td>No</td> - <td>Errors returned via a static <code>gdbm_error</code> - variable</td></tr> -<tr class="odd"><td><a href="http://www.imagemagick.org/">ImageMagick</a></td> - <td>5.2.2</td> - <td>Yes</td> - <td>ImageMagick docs claim it is thread safe since version 5.2.2 (see <a href="http://www.cise.ufl.edu/depot/www/ImageMagick/www/Changelog.html">Change log</a>). - </td></tr> -<tr><td><a href="http://www.enlightenment.org/pages/imlib2.html">Imlib2</a></td> - <td> </td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://www.ijg.org/files/">libjpeg</a></td> - <td>v6b</td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://mysql.com">libmysqlclient</a></td> - <td> </td> - <td>Yes</td> - <td>Use mysqlclient_r library variant to ensure thread-safety. For - more information, please read <a href="http://www.mysql.com/doc/en/Threaded_clients.html">http://www.mysql.com/doc/en/Threaded_clients.html</a>.</td></tr> -<tr class="odd"><td><a href="http://www.opaque.net/ming/">Ming</a></td> - <td>0.2a</td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://net-snmp.sourceforge.net/">Net-SNMP</a></td> - <td>5.0.x</td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://www.openldap.org/">OpenLDAP</a></td> - <td>2.1.x</td> - <td>Yes</td> - <td>Use <code>ldap_r</code> library variant to ensure - thread-safety.</td></tr> -<tr><td><a href="http://www.openssl.org/">OpenSSL</a></td> - <td>0.9.6g</td> - <td>Yes</td> - <td>Requires proper usage of <code>CRYPTO_num_locks</code>, - <code>CRYPTO_set_locking_callback</code>, - <code>CRYPTO_set_id_callback</code></td></tr> -<tr class="odd"><td><a href="http://www.oracle.com/">liboci8 (Oracle 8+)</a></td> - <td>8.x,9.x</td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://pdflib.com/">pdflib</a></td> - <td>5.0.x</td> - <td>Yes</td> - <td>PDFLib docs claim it is thread safe; changes.txt indicates it - has been partially thread-safe since V1.91: <a href="http://www.pdflib.com/products/pdflib/index.html">http://www.pdflib.com/products/pdflib/index.html</a>.</td></tr> -<tr class="odd"><td><a href="http://www.libpng.org/pub/png/libpng.html">libpng</a></td> - <td>1.0.x</td> - <td>?</td> - <td> </td></tr> -<tr><td><a href="http://www.libpng.org/pub/png/libpng.html">libpng</a></td> - <td>1.2.x</td> - <td>?</td> - <td> </td></tr> -<tr class="odd"><td><a href="http://www.postgresql.org/idocs/index.php?libpq-threading.html">libpq (PostgreSQL)</a></td> - <td>7.x</td> - <td>Yes</td> - <td>Don't share connections across threads and watch out for - <code>crypt()</code> calls</td></tr> -<tr><td><a href="http://www.gingerall.com/charlie/ga/xml/p_sab.xml">Sablotron</a></td> - <td>0.95</td> - <td>?</td> - <td /></tr> -<tr class="odd"><td><a href="http://www.gzip.org/zlib/">zlib</a></td> - <td>1.1.4</td> - <td>Yes</td> - <td>Relies upon thread-safe zalloc and zfree functions Default is to - use libc's calloc/free which are thread-safe.</td></tr> -</table> -</div></div> -<div class="bottomlang"> -<p><span>Available Languages: </span><a href="../en/developer/thread_safety.html" title="English"> en </a></p> -</div><div id="footer"> -<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> -<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div> -</body></html>
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