ACE_linux：读写锁

1.涉及类

ACE_RW_Thread_Mutex //ACE读写锁
ACE_Read_Guard //ACE加读锁
ACE_Write_Guard //ACE加写锁
ACE_Thread_Manager //ACE线程管理

2.简介

ACE读/写锁
读/写锁与互斥体相类似。例如，获取读/写锁的线程也必须释放它。多个线程可同时获取一个读/写锁用于读，但只有一个线程可以获取该锁用于写。当互斥体保护的资源用于读远比用于写要频繁时，读/写互斥体有助于改善并发的执行。
ACE线程库提供了一个叫作ACE_RW_Mutex的类，在C++封装类中可移植地实现了读/写锁的语义。读/写锁将优先选择权给写。因而，如果有多个读和一个写在锁上等待，写将会首先获取它。

3.示例代码

#include <iostream>
#include "ace/Thread_Manager.h"
#include "ace/Guard_T.h"
#include "ace/OS_NS_time.h"

using namespace std;
ACE_RW_Thread_Mutex  mutex;

ACE_THR_FUNC_RETURN ThreadFunRead(void *arg) 
{
    ACE_thread_t threadId=ACE_Thread_Manager::instance()->thr_self();

    ACE_Read_Guard<ACE_RW_Thread_Mutex> guard(mutex);
    cout<<"Thread ReadLock  begin  NO:"<<threadId<<endl;


    //ACE_OS::sleep(4);
    cout<<"Thread ReadLock  end    NO:"<<threadId<<endl;
    return NULL; 
} 
ACE_THR_FUNC_RETURN ThreadFunWrite(void *arg) 
{
    ACE_thread_t threadId=ACE_Thread_Manager::instance()->thr_self();

    ACE_Write_Guard<ACE_RW_Thread_Mutex> guard(mutex);
    cout<<"Thread WriteLock begin  NO:"<<threadId<<endl;

    ACE_OS::sleep(1);//休眠1s
    cout<<"Thread WriteLock end    NO:"<<threadId<<endl;
    return NULL; 
}

int main(int argc, char *argv[]) 
{ 
    //1000纳秒=1ms
    timespec_t t;
    t.tv_sec=0;t.tv_nsec=1000;

    ACE_Thread_Manager* pThrMgr = ACE_Thread_Manager::instance();
    //依次一读一写依次3个循环，结果显示是此读写锁写优先。即：加锁等待队列里写操作永远在读前面！
    for(int i=0;i<4;i++)
    {
        pThrMgr->spawn((ACE_THR_FUNC)ThreadFunRead); 
        ACE_OS::nanosleep (&t);
        pThrMgr->spawn((ACE_THR_FUNC)ThreadFunWrite); 
        ACE_OS::nanosleep (&t);
    }
    pThrMgr->wait();

    return 0; 
}

4.示例运行结果

$ ./tt
Thread ReadLock  begin  NO:140015069234944
Thread ReadLock  end    NO:140015069234944
Thread WriteLock begin  NO:140015058745088
Thread WriteLock end    NO:140015058745088
Thread WriteLock begin  NO:140015037765376
Thread WriteLock end    NO:140015037765376
Thread WriteLock begin  NO:140015016785664
Thread WriteLock end    NO:140015016785664
Thread WriteLock begin  NO:140014658778880
Thread WriteLock end    NO:140014658778880
Thread ReadLock  begin  NO:140015048255232
Thread ReadLock  end    NO:140015048255232
Thread ReadLock  begin  NO:140015027275520
Thread ReadLock  end    NO:140015027275520
Thread ReadLock  begin  NO:140015006295808
Thread ReadLock  end    NO:140015006295808

5.Makefile

#bin
THE_INCLUDE      = -I./  
                   -I${ACE_ROOT}/

THE_LIBPATH      = -L./  
                   -L${ACE_ROOT}/lib/
THE_LIB = -g -D_DEBUG_ -lACE# -lxti

CFLAGS = ${THE_LIB} ${THE_INCLUDE} ${THE_LIBPATH}
CC=g++
SRC=$(wildcard *.cpp)
OBJ=$(addprefix ./, $(addsuffix .o, $(basename $(SRC))))
TARGET=tt
all: $(TARGET)
$(TARGET): $(SRC)
    $(CC) -o $@ $^ $(CFLAGS)
    @echo make all done
%.o: %.cpp
    $(CC) $(CFLAGS) -o $@ -c $<
clean:
    rm -f $(TARGET) $(OBJ)

********************************************************************

高级线程(任务)ACE_Task_Base类来创建线程是更方便和优雅

6.示例代码

#include <iostream>
#include "ace/Task.h"

using namespace std;

//静态锁
struct Resource
{
    static ACE_RW_Thread_Mutex  mutex;
};
ACE_RW_Thread_Mutex  Resource::mutex;

class ThreadFunRead : public ACE_Task_Base { 
public: 
    virtual int svc() 
    { 
        ACE_Read_Guard<ACE_RW_Thread_Mutex> guard(Resource::mutex);
        cout<<"Thread ReadLock  begin  NO:"<<ACE_Thread::self()<<endl;

        //ACE_OS::sleep(4);
        cout<<"Thread ReadLock  end    NO:"<<ACE_Thread::self()<<endl;
        return 0;
    }
};

class ThreadFunWrite : public ACE_Task_Base { 
public: 
    virtual int svc() 
    { 
        ACE_Write_Guard<ACE_RW_Thread_Mutex> guard(Resource::mutex);
        cout<<"Thread WriteLock begin  NO:"<<ACE_Thread::self()<<endl;

        ACE_OS::sleep(1);//休眠1s
        cout<<"Thread WriteLock end    NO:"<<ACE_Thread::self()<<endl;
        return 0;
    }
};


int main(int argc, char *argv[]) 
{ 
    //1000纳秒=1ms
    timespec_t t;
    t.tv_sec=0;t.tv_nsec=1000;

    ACE_Thread_Manager* pThrMgr = ACE_Thread_Manager::instance();
    //依次一读一写依次3个循环，结果显示是此读写锁写优先。即：加锁等待队列里写操作永远在读前面！
    for(int i=0;i<4;i++)
    {
        ThreadFunRead  threadRead;
        ThreadFunWrite threadWrite;
        threadRead.activate(); 
        ACE_OS::nanosleep (&t);
        threadWrite.activate(); 
        ACE_OS::nanosleep (&t);
    }

    pThrMgr->wait();

    return 0; 
}