ACE_linux：读写锁

浏览数：28 / 时间：2015年06月20日

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

 1 #include <iostream>
 2 #include "ace/Thread_Manager.h"
 3 #include "ace/Guard_T.h"
 4 #include "ace/OS_NS_time.h"
 5 
 6 using namespace std;
 7 ACE_RW_Thread_Mutex  mutex;
 8 
 9 ACE_THR_FUNC_RETURN ThreadFunRead(void *arg) 
10 {
11     ACE_thread_t threadId=ACE_Thread_Manager::instance()->thr_self();
12 
13     ACE_Read_Guard<ACE_RW_Thread_Mutex> guard(mutex);
14     cout<<"Thread ReadLock  begin  NO:"<<threadId<<endl;
15 
16 
17     //ACE_OS::sleep(4);
18     cout<<"Thread ReadLock  end    NO:"<<threadId<<endl;
19     return NULL; 
20 } 
21 ACE_THR_FUNC_RETURN ThreadFunWrite(void *arg) 
22 {
23     ACE_thread_t threadId=ACE_Thread_Manager::instance()->thr_self();
24 
25     ACE_Write_Guard<ACE_RW_Thread_Mutex> guard(mutex);
26     cout<<"Thread WriteLock begin  NO:"<<threadId<<endl;
27 
28     ACE_OS::sleep(1);//休眠1s
29     cout<<"Thread WriteLock end    NO:"<<threadId<<endl;
30     return NULL; 
31 }
32 
33 int main(int argc, char *argv[]) 
34 { 
35     //1000纳秒=1ms
36     timespec_t t;
37     t.tv_sec=0;t.tv_nsec=1000;
38 
39     ACE_Thread_Manager* pThrMgr = ACE_Thread_Manager::instance();
40     //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！
41     for(int i=0;i<4;i++)
42     {
43         pThrMgr->spawn((ACE_THR_FUNC)ThreadFunRead); 
44         ACE_OS::nanosleep (&t);
45         pThrMgr->spawn((ACE_THR_FUNC)ThreadFunWrite); 
46         ACE_OS::nanosleep (&t);
47     }
48     pThrMgr->wait();
49 
50     return 0; 
51 }

RW_lock.cpp

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

执行结果

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)