C++實現線程死鎖

先上代碼

#include <mutex>
#include <thread>

//#define SLEEP

using namespace std;


class LeftRightDeadLock
{
public:
	void LeftRight(int index)
	{
		mtx_left.lock();
		printf("%d    LeftRight: left in\n", index);
#ifdef SLEEP
		this_thread::sleep_for(300ms);
#endif // SLEEP
		left = 10;

		mtx_right.lock();
		printf("%d    LeftRight: right in\n", index);
#ifdef SLEEP
		this_thread::sleep_for(300ms);
#endif // SLEEP
		right = 20;
		printf("%d    LeftRight: right out\n", index);
		mtx_right.unlock();

		printf("%d    LeftRight: left out\n", index);
		mtx_left.unlock();
	}

	void RightLeft(int index)
	{
		mtx_right.lock();
		printf("%d    RightLeft: right in\n", index);
#ifdef SLEEP
		this_thread::sleep_for(300ms);
#endif // SLEEP
		right = 100;

		mtx_left.lock();
		printf("%d    RightLeft: left in\n", index);
#ifdef SLEEP
		this_thread::sleep_for(300ms);
#endif // SLEEP
		left = 200;
		printf("%d    RightLeft: left out\n", index);
		mtx_left.unlock();

		printf("%d    RightLeft: right out\n", index);
		mtx_right.unlock();
	}


private:
	int left = 0;
	int  right = 0;
	mutex mtx_left;
	mutex mtx_right;
};


LeftRightDeadLock g_l;
mutex g_mtx;

void Test(int index)
{
	//g_mtx.lock();
	printf("index: %d in\n", index);

	g_l.LeftRight(index);
	printf("index: %d middle\n", index);
	g_l.RightLeft(index);

	printf("index: %d out\n\n", index);
	//g_mtx.unlock();
}

int main(int argc, char *argv[])
{
	printf("test begin...\n");
	for (int i = 0; i < 10; ++i)
	{
		thread t(Test, i);
		t.detach();
	}
	printf("test over...\n");
	getchar();
	return 0;
}

運行結果

相信聰明的你一眼就會看出來爲什麼會出現這樣的現象，原因就是產生了死鎖。

如何避免產生死鎖呢？