C++ 不同线程在 FreeBSD 10 上具有相同的线程 ID

Question

我在 FreeBSD 10 机器上使用 C++ 日志库，在收到sigint 时遇到了关闭线程的问题。

A 出于测试目的创建了一个 GitHub 项目 (link)。如果您在 FreeBSD 10 上构建它，执行它并按 [ctrl+c] 它将终止。您可以在下面找到我使用的构建命令。

$ git clone git@github.com:tijme/free-bsd-thread-bug.git
$ cd free-bsd-thread-bug && mkdir -p cmake-build-debug && cd cmake-build-debug
$ cmake .. -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER="/usr/local/bin/gcc6" -DCMAKE_CXX_COMPILER="/usr/local/bin/g++6"
$ make -dA
$ ./FreeBSDThreadBug

我使用的代码（也可以在 GitHub 存储库中找到）

/* main.cpp */

#include "Example.h"
#include <iostream>
#include <csignal>
#include <thread>
#include <chrono>

Example* example = new Example();

void onSignal(int signum)
{
    delete example;
    exit(0);
}

int main() {
    signal(SIGINT, onSignal);

    std::this_thread::sleep_for(std::chrono::milliseconds(5000));

    return 0;
}

/* Example.h */

#ifndef FREEBSDTHREADBUG_EXAMPLE_H
#define FREEBSDTHREADBUG_EXAMPLE_H

#include <thread>
#include <iostream>
#include <chrono>

class Example {

public:
    Example();
    ~Example();
    std::thread threadHandle;
    void threadFunction();
};


#endif //FREEBSDTHREADBUG_EXAMPLE_H

/* Example.cpp */

#include "Example.h"
#include <thread>
#include <chrono>

Example::Example()
{
    std::cout << "Main: starting thread" << std::endl;
    threadHandle = std::thread(&Example::threadFunction, this);
    std::cout << "Main: thread started" << std::endl;
}

Example::~Example()
{
    std::cout << "THIS ID: " << std::this_thread::get_id() << std::endl;
    std::cout << "THREAD ID: " << threadHandle.get_id() << std::endl;

    std::cout << "Main: joining thread" << std::endl;
    threadHandle.join();
    std::cout << "Main: thread joined" << std::endl;
}

void Example::threadFunction() {
    std::cout << "Thread: starting to sleep" << std::endl;
    std::this_thread::sleep_for(std::chrono::milliseconds(2500));
    std::cout << "Thread: sleep finished" << std::endl;
}

正确的输出（例如 MacOS Sierra）：

正如您所见，线程的 ID 与预期的不同。

$ ./FreeBSDThreadBug
Main: starting thread
Main: thread started
Thread: starting to sleep
^C
THIS ID: 0x7fffa428a3c0
THREAD ID: 0x70000c044000
Main: joining thread
Thread: sleep finished
Main: thread joined

错误的输出（终止，在 FreeBSD 10.3 上）：

这里的线程 ID 是一样的，这很奇怪。

$ ./FreeBSDThreadBug 
Main: starting thread
Main: thread started
Thread: starting to sleep
^C
THIS ID: 0x801c06800
THREAD ID: 0x801c06800
Main: joining thread
terminate called after throwing an instance of 'std::system_error'
  what():  Resource deadlock avoided
Abort (core dumped)

核心转储

Core was generated by `FreeBSDThreadBug'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00000008012d335a in thr_kill () from /lib/libc.so.7
[Current thread is 1 (LWP 100146)]
(gdb) bt full
#0  0x00000008012d335a in thr_kill () from /lib/libc.so.7
No symbol table info available.
#1  0x00000008012d3346 in raise () from /lib/libc.so.7
No symbol table info available.
#2  0x00000008012d32c9 in abort () from /lib/libc.so.7
No symbol table info available.
#3  0x0000000800ad8afd in __gnu_cxx::__verbose_terminate_handler () at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/libsupc++/vterminate.cc:95
        terminating = true
        t = <optimized out>
#4  0x0000000800ad5b48 in __cxxabiv1::__terminate (handler=<optimized out>) at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/libsupc++/eh_terminate.cc:47
No locals.
#5  0x0000000800ad5bb1 in std::terminate () at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/libsupc++/eh_terminate.cc:57
No locals.
#6  0x0000000800ad5dc8 in __cxxabiv1::__cxa_throw (obj=obj@entry=0x80200e0a0, tinfo=0x800dd0bc0 <typeinfo for std::system_error>, dest=0x800b073b0 <std::system_error::~system_error()>)
    at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/libsupc++/eh_throw.cc:87
        globals = <optimized out>
#7  0x0000000800b04cd1 in std::__throw_system_error (__i=11) at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/src/c++11/functexcept.cc:130
No locals.
#8  0x0000000800b0792c in std::thread::join (this=0x801c5c058) at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/src/c++11/thread.cc:139
        __e = <optimized out>
#9  0x00000000004016fc in Example::~Example (this=0x801c5c058, __in_chrg=<optimized out>) at /root/FreeBSDThreadBug/Example.cpp:18
No locals.
#10 0x00000000004010b7 in onSignal (signum=2) at /root/FreeBSDThreadBug/main.cpp:11
No locals.
#11 0x000000080082fb4a in ?? () from /lib/libthr.so.3
No symbol table info available.
#12 0x000000080082f22c in ?? () from /lib/libthr.so.3
No symbol table info available.
#13 <signal handler called>
No symbol table info available.
#14 0x00000008012efb5a in _nanosleep () from /lib/libc.so.7
No symbol table info available.
#15 0x000000080082cc4c in ?? () from /lib/libthr.so.3
No symbol table info available.
#16 0x000000000040155d in std::this_thread::sleep_for<long, std::ratio<1l, 1000l> > (__rtime=...) at /usr/local/lib/gcc6/include/c++/thread:322
        __s = {__r = 2}
        __ns = {__r = 500000000}
        __ts = {tv_sec = 1, tv_nsec = 126917539}
#17 0x000000000040177a in Example::threadFunction (this=0x801c5c058) at /root/FreeBSDThreadBug/Example.cpp:24
No locals.
#18 0x0000000000402432 in std::__invoke_impl<void, void (Example::* const&)(), Example*>(std::__invoke_memfun_deref, void (Example::* const&)(), Example*&&) (
    __f=@0x801c5e050: (void (Example::*)(Example * const)) 0x40172c <Example::threadFunction()>, __t=<unknown type in /root/FreeBSDThreadBug/cmake-build-debug/FreeBSDThreadBug, CU 0x552f, DIE 0xb2d7>)
    at /usr/local/lib/gcc6/include/c++/functional:227
No locals.
#19 0x00000000004023bf in std::__invoke<void (Example::* const&)(), Example*>(void (Example::* const&)(), Example*&&) (__fn=@0x801c5e050: (void (Example::*)(Example * const)) 0x40172c <Example::threadFunction()>, 
    __args#0=<unknown type in /root/FreeBSDThreadBug/cmake-build-debug/FreeBSDThreadBug, CU 0x552f, DIE 0xb2d7>) at /usr/local/lib/gcc6/include/c++/functional:251
No locals.
#20 0x0000000000402370 in std::_Mem_fn_base<void (Example::*)(), true>::operator()<Example*>(Example*&&) const (this=0x801c5e050, 
    __args#0=<unknown type in /root/FreeBSDThreadBug/cmake-build-debug/FreeBSDThreadBug, CU 0x552f, DIE 0xb2d7>) at /usr/local/lib/gcc6/include/c++/functional:604
No locals.
#21 0x000000000040233b in std::_Bind_simple<std::_Mem_fn<void (Example::*)()> (Example*)>::_M_invoke<0ul>(std::_Index_tuple<0ul>) (this=0x801c5e048) at /usr/local/lib/gcc6/include/c++/functional:1391
No locals.
#22 0x0000000000402289 in std::_Bind_simple<std::_Mem_fn<void (Example::*)()> (Example*)>::operator()() (this=0x801c5e048) at /usr/local/lib/gcc6/include/c++/functional:1380
No locals.
#23 0x0000000000402268 in std::thread::_State_impl<std::_Bind_simple<std::_Mem_fn<void (Example::*)()> (Example*)> >::_M_run() (this=0x801c5e040) at /usr/local/lib/gcc6/include/c++/thread:196
No locals.
#24 0x0000000800b0769f in std::execute_native_thread_routine (__p=0x801c5e040) at /wrkdirs/usr/ports/lang/gcc6/work/gcc-6.3.0/libstdc++-v3/src/c++11/thread.cc:83
        __t = std::unique_ptr<std::thread::_State> containing 0x801c5e040
#25 0x000000080082a855 in ?? () from /lib/libthr.so.3
No symbol table info available.
#26 0x0000000000000000 in ?? ()
No symbol table info available.
Backtrace stopped: Cannot access memory at address 0x7fffdfffe000

系统信息

$ freebsd-version
10.3-RELEASE

$ /usr/local/bin/gcc6 --version
gcc6 (FreeBSD Ports Collection) 6.3.0

$ /usr/local/bin/g++6 --version
g++6 (FreeBSD Ports Collection) 6.3.0

$ cmake --version
cmake version 3.7.2

我创建的原始问题可以在 GitHub (link) 上找到，但是还没有修复。

我希望有人能够帮助我解决这个问题。提前致谢。

Answer 1

这不是错误，这是一项功能。

您无法保证您的信号将被传递到哪里，并且您可以在信号处理程序中执行的一系列操作受到限制。

请参阅sigaction(3) 了解有关您可以做什么（并且您不能做其他任何事情）的详细信息。您的程序正在执行信号处理程序中不允许的许多事情。

正确的做法是在程序中发出其他信号并从信号处理程序返回。这样做的一个示例技术是“自我管道技巧”。创建一个管道并在两端保留一个句柄。在您的正常 I/O 处理中从一端读取​​。如果您收到信号，则在信号处理程序中，将一个字节写入管道的另一端并返回。当从管道中读取字节时，您就知道信号已经到达，您可以安全地进行扩展处理。

更新：

正如 Michael Burr 所指出的，您可以使用 pthread_sigmask(3) 阻止特定线程接收特定信号。但是，要解决这里的潜在问题，您仍然不需要在信号处理程序中进行工作。