一道关于lock的面试题# JobHunting - 待字闺中
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大家都知道lock吧，thread synchronization用的。
这个题目是这样的：
假设我们有一个现成的library提供了基本的reader／writer lock功能:
class Lock {
public:
Lock();
// exclusive writer lock
void GetLock();
void ReleaseLock();
// shared reader lock
void GetReaderLock();
void ReleaseReaderLock();
};
Problem 1: implement a functionality to atomically upgrade a reader lock to
writer lock, if no one else is holding reader lock
Problem 2: implement a functionality to manage lock per keys, i.e.:
template
class LockManager {
void GetLock(KeyType key);
void ReleaseLock(KeyType key);
void GetReaderLock(KeyType key);
void ReleaseReaderLock(KeyType key);
}
requirement:
a. able to lock/unlock on different keys concurrently
b. keep memory space linear to the size of "active keys", i.e., if no one is
holding lock for a key, you need to do garbage collect for that key.
这个题目是这样的：
假设我们有一个现成的library提供了基本的reader／writer lock功能:
class Lock {
public:
Lock();
// exclusive writer lock
void GetLock();
void ReleaseLock();
// shared reader lock
void GetReaderLock();
void ReleaseReaderLock();
};
Problem 1: implement a functionality to atomically upgrade a reader lock to
writer lock, if no one else is holding reader lock
Problem 2: implement a functionality to manage lock per keys, i.e.:
template
class LockManager {
void GetLock(KeyType key);
void ReleaseLock(KeyType key);
void GetReaderLock(KeyType key);
void ReleaseReaderLock(KeyType key);
}
requirement:
a. able to lock/unlock on different keys concurrently
b. keep memory space linear to the size of "active keys", i.e., if no one is
holding lock for a key, you need to do garbage collect for that key.