n*****g
发帖数: 178 | 1 题目是CC150第五版16.5题，题目是这样的：
Suppose we have the following code:
public class Foo {
public Foo() { . . . }
public void first() { ... }
public void second() { ... }
public void thirdQ { ... }
The same instance of Foo will be passed to three different threads. ThreadA
will call first, threads will call second, and threadC will call third.
Design a mechanism to ensure that first is called before second and second
is called before third.
这要换成C语言来问的话，是不是等同于这样问：一个foo函数，确保foo先被first调用
，然后再被second和third调用（first，second，和third来自不同的thread）？
如果等同话 ，用C语言，Semaphore如何解答呢？
我的想法是：
void first（）
{
signal(sem1);
}
void second()
{
wait(sem1);
signal(sem2);
}
void third()
{
wait(sem2);
}
感觉这样写有点问题，求指教！ |
s*****n
发帖数: 5488 | 2 有什么问题？semiphore太heavy了吧。不如用condition variable.
ThreadA
【在 n*****g 的大作中提到】
: 题目是CC150第五版16.5题，题目是这样的：
: Suppose we have the following code:
: public class Foo {
: public Foo() { . . . }
: public void first() { ... }
: public void second() { ... }
: public void thirdQ { ... }
: The same instance of Foo will be passed to three different threads. ThreadA
: will call first, threads will call second, and threadC will call third.
: Design a mechanism to ensure that first is called before second and second
|
n*****g
发帖数: 178 | 3
貌似我搞混了，这里我用wait和signal其实就是想用condition variable。
不过cond应该和mutex一起用吧？我觉得应该这么写，不知道有没问题：
void first（）
{
lock();
signal(second);
unlock();
}
void second()
{
lock();
wait(first);
unlock();
lock();
signal(third);
unlock();
}
void third()
{
lock();
wait(second);
unlock();
}
【在 s*****n 的大作中提到】
: 有什么问题？semiphore太heavy了吧。不如用condition variable.
:
: ThreadA
|
g**x
发帖数: 373 | 4 int i=0;
mutex m;
cond c;
void first() {
{
lock(m);
i++;
signal(c);
unlock(m);
}
void second() {
lock(m);
while (i!=1) {
wait(m, c);
}
i++;
signal(c);
unlock(m);
}
void third() {
lock(m);
while (i!=2) {
wait(m,c);
}
//...
unlock(m);
}
【在 n*****g 的大作中提到】
:
: 貌似我搞混了，这里我用wait和signal其实就是想用condition variable。
: 不过cond应该和mutex一起用吧？我觉得应该这么写，不知道有没问题：
: void first（）
: {
: lock();
: signal(second);
: unlock();
: }
: void second()
|
n*****g
发帖数: 178 | 5
ThreadA
不知道三楼的对吗？
【在 n*****g 的大作中提到】
: 题目是CC150第五版16.5题，题目是这样的：
: Suppose we have the following code:
: public class Foo {
: public Foo() { . . . }
: public void first() { ... }
: public void second() { ... }
: public void thirdQ { ... }
: The same instance of Foo will be passed to three different threads. ThreadA
: will call first, threads will call second, and threadC will call third.
: Design a mechanism to ensure that first is called before second and second
|
