ACE线程之ACE_Thread_Mutex互斥锁

    互斥体实现了互相排斥（mutual exclusion）同步的简单形式。互斥体禁止多个线程同时进入受保护的代码临界区（critical section）。因此，在任意时刻，只有一个线程被允许进入这样代码保护区。

    任何线程在进入临界区之前，必须获取acquire与此区域相关的互斥体的所有权。如果已有另一线程拥有了临界区互斥体，其他线程就不能再进入其中。这些线程必须等待，知道当前的属主线程释放release该互斥体。

    什么时候需要使用互斥体呢？互斥体用于保护共享的易变代码，也就是，全局或静态数据。这样的数据必须通过互斥体进行保护，以防止它们在多个线程同时访问时损坏。 

如下示例：

#include <QtCore/QCoreApplication>#include "ace/Synch.h"#include "ace/Log_Msg.h"   //ace_debug#include "ace/OS_NS_stdio.h"   ///ACE_OS::printf#include "ace/Thread.h"struct Args{public:Args(int iterations):mutex_(),iterations_(iterations) {}ACE_Thread_Mutex mutex_;int iterations_;};///the starting point for the worker threadsstatic void* worker(void *arguments){Args *arg= (Args*) arguments;for(int i=0; i<arg->iterations_; i++){ACE_DEBUG((LM_DEBUG,"(%t) Trying to get a hold of this iteration\n"));///this is our critical sectionarg->mutex_.acquire();      ///acquire: 获得ACE_DEBUG((LM_DEBUG,"(%t) This is iteration number %d\n",i));ACE_OS::sleep(2);//simulate critical（关键，临界） workarg->mutex_.release();}return 0;}int main(int argc, char *argv[]){QCoreApplication a(argc, argv);if(argc<2){ACE_OS::printf("Usage: %s <number_of_threads> <num_of_iterations>\n",argv[0]);ACE_OS::exit(1);}Args arg(ACE_OS::atoi(argv[2]));//setup the argumentsint n_threads= ACE_OS::atoi(argv[1]);ACE_thread_t *threadID=new ACE_thread_t[n_threads+1];          ///DWORDACE_hthread_t *threadHandles=new ACE_hthread_t[n_threads+1];   ///HANDLEif(ACE_Thread::spawn_n(threadID,    ////id's for each of the threads                 n_threads,   ////number of threads to spawn (ACE_THR_FUNC)worker, ///entry point for new thread &arg,        ////args to worker THR_JOINABLE | THR_NEW_LWP,  //flags ACE_DEFAULT_THREAD_PRIORITY, 0,0,threadHandles)==-1){ACE_DEBUG((LM_DEBUG,"Error in spawning thread\n"));}for(int i=0; i<n_threads; i++)ACE_Thread::join(threadHandles[i]);return 0;///a.exec();}

(9912) Trying to get a hold of this iteration
(9912) This is iteration number 0
(7312) Trying to get a hold of this iteration
(7312) This is iteration number 0
(9912) Trying to get a hold of this iteration
(9912) This is iteration number 1
(7312) Trying to get a hold of this iteration
(9912) Trying to get a hold of this iteration
(7312) This is iteration number 1
(7312) Trying to get a hold of this iteration
(9912) This is iteration number 2
(9912) Trying to get a hold of this iteration
(7312) This is iteration number 2
(7312) Trying to get a hold of this iteration
(7312) This is iteration number 3
(9912) This is iteration number 3
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