lock_when 枚举
指定延迟锁定。
语法
enum lock_when {
lock_later
};
备注
传递给 lock::lock 时,lock_later
指定现在不执行锁定。
示例
此示例跨多个线程使用类的单个实例。 该类对自身使用锁定,以确保对其内部数据的访问对于每个线程都是一致的。 主应用程序线程对该类的相同实例使用锁定,以定期检查是否存在任何工作线程,并等待退出,直到所有工作线程都已完成其任务。
// msl_lock_lock_when.cpp
// compile with: /clr
#include <msclr/lock.h>
using namespace System;
using namespace System::Threading;
using namespace msclr;
ref class CounterClass {
private:
int Counter;
public:
property int ThreadCount;
// function called by multiple threads, use lock to keep Counter consistent
// for each thread
void UseCounter() {
try {
lock l(this); // wait infinitely
Console::WriteLine("In thread {0}, Counter = {1}", Thread::CurrentThread->ManagedThreadId,
Counter);
for (int i = 0; i < 10; i++) {
Counter++;
Thread::Sleep(10);
}
Console::WriteLine("In thread {0}, Counter = {1}", Thread::CurrentThread->ManagedThreadId,
Counter);
Counter = 0;
// lock is automatically released when it goes out of scope and its destructor is called
}
catch (...) {
Console::WriteLine("Couldn't acquire lock!");
}
ThreadCount--;
}
};
int main() {
// create a few threads to contend for access to the shared data
CounterClass^ cc = gcnew CounterClass;
array<Thread^>^ tarr = gcnew array<Thread^>(5);
ThreadStart^ startDelegate = gcnew ThreadStart(cc, &CounterClass::UseCounter);
for (int i = 0; i < tarr->Length; i++) {
tarr[i] = gcnew Thread(startDelegate);
cc->ThreadCount++;
tarr[i]->Start();
}
// keep our main thread alive until all worker threads have completed
lock l(cc, lock_later); // don't lock now, just create the object
while (true) {
if (l.try_acquire(50)) { // try to acquire lock, don't throw an exception if can't
if (0 == cc->ThreadCount) {
Console::WriteLine("All threads completed.");
break; // all threads are gone, exit while
}
else {
Console::WriteLine("{0} threads exist, continue waiting...", cc->ThreadCount);
l.release(); // some threads exist, let them do their work
}
}
}
}
In thread 3, Counter = 0
In thread 3, Counter = 10
In thread 5, Counter = 0
In thread 5, Counter = 10
In thread 7, Counter = 0
In thread 7, Counter = 10
In thread 4, Counter = 0
In thread 4, Counter = 10
In thread 6, Counter = 0
In thread 6, Counter = 10
All threads completed.
要求
头文件 <msclr\lock.h>
命名空间 msclr