Experimental operation process
First use suthe command to switch the user to the root user,
Compile threadpool.cpp and threadpool.h into a dynamic library
jyhlinux@ubuntu:~/share/threadpool$ g++ -fPIC -shared threadpool.cpp -o libtdpool.so -std=c++17
Put the generated library and header files in the system directory , and delete the source files
root@ubuntu:/home/jyhlinux/share/threadpool# mv libtdpool.so /usr/local/lib/
root@ubuntu:/home/jyhlinux/share/threadpool# ls
test_threadpool.cpp threadpool.cpp threadpool.h
root@ubuntu:/home/jyhlinux/share/threadpool# rm threadpool.cpp
root@ubuntu:/home/jyhlinux/share/threadpool# mv threadpool.h /usr/local/include/
Compile and link to generate source files
root@ubuntu:/home/jyhlinux/share/threadpool# g++ test_threadpool.cpp -std=c++17 -ltdpool -lpthread
Executes the executable but fails because the runtime system looks for dynamic libraries in a different location
The runtime system /etc/ld.so.cachelooks for the dynamic library link in the file
Do the following to add configuration
root@ubuntu:/etc/ld.so.conf.d# vim /etc/ld.so.conf
Add a line /usr/local/lib
Then go back to the test file path and refresh the dynamic library configuration
jyhlinux@ubuntu:/etc/ld.so.conf.d$ cd ~/share/threadpool
jyhlinux@ubuntu:~/share/threadpool$ sudo ldconfig
Execute the program again, the program runs normally, and the garbled characters are encoding problems
some problems
Problem Description
If it is an old version of g++, there may be a deadlock phenomenon, because the condition_variabledestructor under g++ does not do anything, causing Semaphorethe class notifyto block:
void post()
{
std::unique_lock<std::mutex> lock(mtx_);
resLimit_++;
cond_.notify_all(); // 阻塞在这里！！！
}
Threads can be debugged with gdb
gdb attach 进程号 #调试进程
info threads #查看进程中所有线程，前面有*代表当前线程
thread id #切换到info threads查看的线程id
bt #查看线程调用堆栈
Solution
You can add a value Semaphoreto the class to indicate whether it has exited. If you exit, do not perform lock and and operations. The modified class isboolwait notifySemaphore
class Semaphore
{
public:
Semaphore(int limit = 0)
:resLimit_(limit)
{
}
~Semaphore()
{
isExit_ = true;
}
void wait()
{
if(isExit_) return ; //
std::unique_lock<std::mutex> lock(mtx_);
cond_.wait(lock, [&]()->bool {
return resLimit_ > 0; }); //
resLimit_--;
}
void post()
{
if(isExit_) return ;//
std::unique_lock<std::mutex> lock(mtx_);
resLimit_++;
cond_.notify_all();
}
private:
std::atomic_bool isExit_;//
int resLimit_;
std::mutex mtx_;
std::condition_variable cond_;
};