example3_7.cpp

//使用锁层次来避免死锁
hierarchical_mutex high_level_mutex(10000);
hierarchical_mutex low_level_mutex(5000);

int do_low_level_stuff();

int low_level_func()
{
	std::lock_guard<hierarchical_mutex> lk(low_level_mutex);
	return do_low_level_stuff();
}

void high_level_stuff(int some_param);

void high_level_func()
{
	std::lock_guard<hierarchical_mutex> lk(high_level_mutex);
	high_level_stuff(low_level_func());
}

void thread_a()	//遵守规则，运行良好
{
	high_level_func();
}

hierarchical_mutex other_mutex(100);
void do_other_stuff();

void other_stuff()
{
	high_level_func();
	do_other_stuff();
}

//违反层次，100<1000
void thread_b()	
{
	std::lock_guard<hierarchical_mutex> lk(other_mutex);
	other_stuff();
}