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[tsan] first version of ThreadSanitizer docs
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156910 91177308-0d34-0410-b5e6-96231b3b80d8
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Kostya Serebryany
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ -->
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<html>
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<head>
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<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>ThreadSanitizer, a race detector</title>
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<link type="text/css" rel="stylesheet" href="../menu.css">
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<link type="text/css" rel="stylesheet" href="../content.css">
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<style type="text/css">
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td {
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vertical-align: top;
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}
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</style>
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</head>
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<body>
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<!--#include virtual="../menu.html.incl"-->
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<div id="content">
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<h1>ThreadSanitizer</h1>
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<ul>
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<li> <a href="#intro">Introduction</a>
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<li> <a href="#howtobuild">How to Build</a>
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<li> <a href="#platforms">Supported Platforms</a>
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<li> <a href="#usage">Usage</a>
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<li> <a href="#limitations">Limitations</a>
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<li> <a href="#status">Current Status</a>
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<li> <a href="#moreinfo">More Information</a>
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</ul>
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<h2 id="intro">Introduction</h2>
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ThreadSanitizer is a tool that detects data races. <BR>
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It consists of a compiler instrumentation module and a run-time library. <BR>
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Typical slowdown introduced by ThreadSanitizer is <b>5x-15x</b> (TODO: these numbers are
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aproximate so far).
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<h2 id="howtobuild">How to build</h2>
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Follow the <a href="../get_started.html">clang build instructions</a>. <BR>
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Note: CMake build does not work yet.
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See <a href="http://llvm.org/bugs/show_bug.cgi?id=12272">bug 12272</a>.
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<h2 id="platforms">Supported Platforms</h2>
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ThreadSanitizer is supported on Linux x86_64 (tested on Ubuntu 10.04). <BR>
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Support for MacOS 10.7 (64-bit only) is planed for late 2012. <BR>
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Support for 32-bit platforms is problematic and not yet planed.
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<h2 id="usage">Usage</h2>
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Simply compile your program with <tt>-faddress-sanitizer -fPIE</tt> and link it
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with <tt>-faddress-sanitizer -pie</tt>.<BR>
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To get a reasonable performance add <tt>-O1</tt> or higher. <BR>
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Use <tt>-g</tt> to get file names and line numbers in the warning messages. <BR>
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Example:
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<pre>
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% cat projects/compiler-rt/lib/tsan/output_tests/tiny_race.c
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#include <pthread.h>
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int Global;
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void *Thread1(void *x) {
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Global = 42;
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return x;
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}
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int main() {
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pthread_t t;
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pthread_create(&t, NULL, Thread1, NULL);
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Global = 43;
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pthread_join(t, NULL);
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return Global;
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}
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</pre>
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<pre>
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% clang -fthread-sanitizer -g -O1 tiny_race.c -fPIE -pie
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</pre>
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If a bug is detected, the program will print an error message to stderr.
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Currently, ThreadSanitizer symbolizes its output using an external
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<tt>addr2line</tt>
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process (this will be fixed in future).
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<pre>
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% TSAN_OPTIONS=strip_path_prefix=`pwd`/ # Don't print full paths.
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% ./a.out 2> log
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% cat log
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WARNING: ThreadSanitizer: data race (pid=19219)
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Write of size 4 at 0x7fcf47b21bc0 by thread 1:
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#0 Thread1 tiny_race.c:4 (exe+0x00000000a360)
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Previous write of size 4 at 0x7fcf47b21bc0 by main thread:
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#0 main tiny_race.c:10 (exe+0x00000000a3b4)
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Thread 1 (running) created at:
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#0 pthread_create ??:0 (exe+0x00000000c790)
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#1 main tiny_race.c:9 (exe+0x00000000a3a4)
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</pre>
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<h2 id="limitations">Limitations</h2>
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<ul>
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<li> ThreadSanitizer uses more real memory than a native run.
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At the default settings the memory overhead is 9x plus 9Mb per each thread.
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Settings with 5x and 3x overhead (but less accurate analysis) are also available.
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<li> ThreadSanitizer maps (but not reserves) a lot of virtual address space.
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This means that tools like <tt>ulimit</tt> may not work as usually expected.
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<li> Static linking is not supported.
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<li> ThreadSanitizer requires <tt>-fPIE -pie</tt>
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</ul>
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<h2 id="status">Current Status</h2>
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ThreadSanitizer is in alpha stage.
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It is known to work on large C++ programs using pthreads, but we do not promise
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anything (yet). <BR>
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C++11 threading is not yet supported.
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We are actively working on enhancing the tool -- stay tuned.
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Any help, especially in the form of minimized standalone tests is more than welcome.
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<h2 id="moreinfo">More Information</h2>
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<a href="http://code.google.com/p/thread-sanitizer/">http://code.google.com/p/thread-sanitizer</a>.
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</div>
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</body>
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</html>
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