| Kostya Serebryany | e2789bb | 2012-05-16 08:14:36 +0000 | [diff] [blame] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" |
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| 7 | <title>ThreadSanitizer, a race detector</title> |
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| 21 | |
| 22 | <h1>ThreadSanitizer</h1> |
| 23 | <ul> |
| 24 | <li> <a href="#intro">Introduction</a> |
| 25 | <li> <a href="#howtobuild">How to Build</a> |
| 26 | <li> <a href="#platforms">Supported Platforms</a> |
| 27 | <li> <a href="#usage">Usage</a> |
| 28 | <li> <a href="#limitations">Limitations</a> |
| 29 | <li> <a href="#status">Current Status</a> |
| 30 | <li> <a href="#moreinfo">More Information</a> |
| 31 | </ul> |
| 32 | |
| 33 | <h2 id="intro">Introduction</h2> |
| 34 | ThreadSanitizer is a tool that detects data races. <BR> |
| 35 | It consists of a compiler instrumentation module and a run-time library. <BR> |
| 36 | Typical slowdown introduced by ThreadSanitizer is <b>5x-15x</b> (TODO: these numbers are |
| 37 | aproximate so far). |
| 38 | |
| 39 | <h2 id="howtobuild">How to build</h2> |
| 40 | Follow the <a href="../get_started.html">clang build instructions</a>. <BR> |
| 41 | Note: CMake build does not work yet. |
| 42 | See <a href="http://llvm.org/bugs/show_bug.cgi?id=12272">bug 12272</a>. |
| 43 | |
| 44 | <h2 id="platforms">Supported Platforms</h2> |
| 45 | ThreadSanitizer is supported on Linux x86_64 (tested on Ubuntu 10.04). <BR> |
| 46 | Support for MacOS 10.7 (64-bit only) is planed for late 2012. <BR> |
| 47 | Support for 32-bit platforms is problematic and not yet planed. |
| 48 | |
| 49 | |
| 50 | |
| 51 | <h2 id="usage">Usage</h2> |
| Kostya Serebryany | 5324380 | 2012-05-16 08:19:13 +0000 | [diff] [blame] | 52 | Simply compile your program with <tt>-fthread-sanitizer -fPIE</tt> and link it |
| 53 | with <tt>-fthread-sanitizer -pie</tt>.<BR> |
| Kostya Serebryany | e2789bb | 2012-05-16 08:14:36 +0000 | [diff] [blame] | 54 | To get a reasonable performance add <tt>-O1</tt> or higher. <BR> |
| 55 | Use <tt>-g</tt> to get file names and line numbers in the warning messages. <BR> |
| 56 | |
| 57 | Example: |
| 58 | <pre> |
| 59 | % cat projects/compiler-rt/lib/tsan/output_tests/tiny_race.c |
| 60 | #include <pthread.h> |
| 61 | int Global; |
| 62 | void *Thread1(void *x) { |
| 63 | Global = 42; |
| 64 | return x; |
| 65 | } |
| 66 | int main() { |
| 67 | pthread_t t; |
| 68 | pthread_create(&t, NULL, Thread1, NULL); |
| 69 | Global = 43; |
| 70 | pthread_join(t, NULL); |
| 71 | return Global; |
| 72 | } |
| 73 | </pre> |
| 74 | |
| 75 | <pre> |
| 76 | % clang -fthread-sanitizer -g -O1 tiny_race.c -fPIE -pie |
| 77 | </pre> |
| 78 | |
| 79 | If a bug is detected, the program will print an error message to stderr. |
| 80 | Currently, ThreadSanitizer symbolizes its output using an external |
| 81 | <tt>addr2line</tt> |
| 82 | process (this will be fixed in future). |
| 83 | <pre> |
| 84 | % TSAN_OPTIONS=strip_path_prefix=`pwd`/ # Don't print full paths. |
| 85 | % ./a.out 2> log |
| 86 | % cat log |
| 87 | WARNING: ThreadSanitizer: data race (pid=19219) |
| 88 | Write of size 4 at 0x7fcf47b21bc0 by thread 1: |
| 89 | #0 Thread1 tiny_race.c:4 (exe+0x00000000a360) |
| 90 | Previous write of size 4 at 0x7fcf47b21bc0 by main thread: |
| 91 | #0 main tiny_race.c:10 (exe+0x00000000a3b4) |
| 92 | Thread 1 (running) created at: |
| 93 | #0 pthread_create ??:0 (exe+0x00000000c790) |
| 94 | #1 main tiny_race.c:9 (exe+0x00000000a3a4) |
| 95 | </pre> |
| 96 | |
| 97 | |
| 98 | <h2 id="limitations">Limitations</h2> |
| 99 | <ul> |
| 100 | <li> ThreadSanitizer uses more real memory than a native run. |
| 101 | At the default settings the memory overhead is 9x plus 9Mb per each thread. |
| 102 | Settings with 5x and 3x overhead (but less accurate analysis) are also available. |
| 103 | <li> ThreadSanitizer maps (but not reserves) a lot of virtual address space. |
| 104 | This means that tools like <tt>ulimit</tt> may not work as usually expected. |
| 105 | <li> Static linking is not supported. |
| 106 | <li> ThreadSanitizer requires <tt>-fPIE -pie</tt> |
| 107 | </ul> |
| 108 | |
| 109 | |
| 110 | <h2 id="status">Current Status</h2> |
| 111 | ThreadSanitizer is in alpha stage. |
| 112 | It is known to work on large C++ programs using pthreads, but we do not promise |
| 113 | anything (yet). <BR> |
| 114 | C++11 threading is not yet supported. |
| 115 | |
| 116 | We are actively working on enhancing the tool -- stay tuned. |
| 117 | Any help, especially in the form of minimized standalone tests is more than welcome. |
| 118 | |
| 119 | <h2 id="moreinfo">More Information</h2> |
| 120 | <a href="http://code.google.com/p/thread-sanitizer/">http://code.google.com/p/thread-sanitizer</a>. |
| 121 | |
| 122 | |
| 123 | </div> |
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