英文:
Thread Sanitizer and Intel OpenMP
问题
We are using GCC and Intel OpenMP.
我知道GCC和GCC OpenMP的组合需要一个特殊的OpenMP版本（使用pthread接口而不是直接使用futex系统调用）。
能否使用Thread Sanitizer和GCC + Intel OpenMP？显然，我不能简单地重新编译Intel OpenMP库。
我已经开始了一个测试，但出现了如下错误：
Atomic read of size 1 at 0x7fffec302980 by thread T4:
#0 pthread_mutex_lock ../../../../libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:4250 (libtsan.so.0+0x52d1a)
#1 __kmp_resume_64 <null> (libiomp5.so+0xb7ae3)
Previous write of size 1 at 0x7fffec302980 by thread T7:
#0 pthread_mutex_init ../../../../libsanitizer/tsan/tsan_interceptors_posix.cpp:1227 (libtsan.so.0+0x4c343)
#1 __kmp_suspend_64 <null> (libiomp5.so+0xb587b)
Thread T4 (tid=15590, running) created by main thread at:
#0 pthread_create ../../../../libsanitizer/tsan/tsan_interceptors_posix.cpp:969 (libtsan.so.0+0x5ec85)
#1 __kmp_create_worker <null> (libiomp5.so+0xb1a34)
我有点假设带有__kmp前缀的内容应该是安全的，这个错误是因为Thread Sanitizer没有封装任何__kmp函数。
英文:
We are using GCC and Intel OpenMP.
I know that the combination of GCC and GCC OpenMP needs a special build of OpenMP (to use pthread interfaces rather than directly use the futex system call).
Is it possible to use Thread Sanitizer and GCC + Intel OpenMP? Obviously I can't just simply recompile the Intel OpenMP library.
I've started a test and I'm getting errors like
WARNING: ThreadSanitizer: data race (pid=15551)
Atomic read of size 1 at 0x7fffec302980 by thread T4:
#0 pthread_mutex_lock ../../../../libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:4250 (libtsan.so.0+0x52d1a)
#1 __kmp_resume_64 <null> (libiomp5.so+0xb7ae3)
Previous write of size 1 at 0x7fffec302980 by thread T7:
#0 pthread_mutex_init ../../../../libsanitizer/tsan/tsan_interceptors_posix.cpp:1227 (libtsan.so.0+0x4c343)
#1 __kmp_suspend_64 <null> (libiomp5.so+0xb587b)
Thread T4 (tid=15590, running) created by main thread at:
#0 pthread_create ../../../../libsanitizer/tsan/tsan_interceptors_posix.cpp:969 (libtsan.so.0+0x5ec85)
#1 __kmp_create_worker <null> (libiomp5.so+0xb1a34)
I kind of assume that anything with the __kmp prefix should be safe, and this error is because Thread Sanitizer does not encapsulate any __kmp functions.
答案1
得分: 1
First, TSan by it's own does not understand OpenMP synchronization like barriers or task dependencies. We developed libarcher as part of LLVM to feed this information into TSan.
如果单独使用TSan，它无法理解OpenMP的同步，比如栅栏或任务依赖。我们在LLVM的一部分中开发了libarcher，以将这些信息传递给TSan。
If you compile a code with clang -fopenmp -fsanitize=thread, libarcher will automatically be loaded and support TSan. (verify successful loading by exporting export ARCHER_OPTIONS=verbose=true).
如果使用clang -fopenmp -fsanitize=thread编译代码，libarcher将自动加载并支持TSan。（通过导出export ARCHER_OPTIONS=verbose=true来验证加载是否成功）。
libarcher needs OMPT support in the OpenMP runtime, which libgomp does not provide yet.
libarcher需要OpenMP运行时中的OMPT支持，而libgomp目前尚不提供。
libarcher also works with newer Intel OpenMP runtimes (2020+), by explicitly loading it as an OMPT tool: export OMP_TOOL_LIBRARIES=<path-to>/libarcher.so
libarcher还与较新的Intel OpenMP运行时（2020+）兼容，通过显式加载它作为OMPT工具：export OMP_TOOL_LIBRARIES=<path-to>/libarcher.so
To get libarcher you can build from source.
要获取libarcher，你可以从源代码构建。
The source code is contained in the LLVM/OpenMP project:
源代码包含在LLVM/OpenMP项目中：
https://github.com/llvm/llvm-project/releases/download/llvmorg-16.0.6/openmp-16.0.6.src.tar.xz
tar xf openmp-16.0.6.src.tar.xz
cd openmp-16.0.6
mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DOPENMP_ENABLE_LIBOMPTARGET=False -DCMAKE_INSTALL_PREFIX=$PWD/install
make -j install
should install the code to openmp-16.0.6/build/install/, so libarcher should be in openmp-16.0.6/build/install/lib/libarcher.so
应该将代码安装到openmp-16.0.6/build/install/，因此libarcher应该位于openmp-16.0.6/build/install/lib/libarcher.so
Second, for the issue of false reports from OpenMP runtime code, I suggest
其次，对于OpenMP运行时代码的虚假报告问题，我建议：
export TSAN_OPTIONS='ignore_noninstrumented_modules=1'
This will disable the detection of any data race caused from non-instrumented code. So, if you link to other non-instrumented libraries (e.g. BLAS) they will also be ignored. The picture TSan gets for such libraries is limited to intercepted libc functions anyways.
这将禁用对非受仪器监测的代码引起的任何数据竞争的检测。因此，如果你链接到其他非受仪器监测的库（例如BLAS），它们也将被忽略。对于这种类型的库，TSan获取的信息本来就受限于被拦截的libc函数。
英文:
First, TSan by it's own does not understand OpenMP synchronization like barriers or task dependencies. We developed libarcher as part of LLVM to feed this information into TSan.
If you compile a code with clang -fopenmp -fsanitize=thread, libarcher will automatically be loaded and support TSan. (verify successful loading by exporting export ARCHER_OPTIONS=verbose=true).
libarcher needs OMPT support in the OpenMP runtime, which libgomp does not provide yet.
libarcher also works with newer Intel OpenMP runtimes (2020+), by explicitly loading it as an OMPT tool: export OMP_TOOL_LIBRARIES=<path-to>/libarcher.so
To get libarcher you can build from source.
The source code is contained in the LLVM/OpenMP project:
https://github.com/llvm/llvm-project/releases/download/llvmorg-16.0.6/openmp-16.0.6.src.tar.xz
tar xf openmp-16.0.6.src.tar.xz
cd openmp-16.0.6
mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DOPENMP_ENABLE_LIBOMPTARGET=False -DCMAKE_INSTALL_PREFIX=$PWD/install
make -j install
should install the code to openmp-16.0.6/build/install/, so libarcher should be in openmp-16.0.6/build/install/lib/libarcher.so
Second, for the issue of false reports from OpenMP runtime code, I suggest
export TSAN_OPTIONS='ignore_noninstrumented_modules=1'
This will disable the detection of any data race caused from non-instrumented code. So, if you link to other non-instrumented libraries (e.g. BLAS) they will also be ignored. The picture TSan gets for such libraries is limited to intercepted libc functions anyways.
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