c# - C# ReaderWriteLock 中可升级读锁与写锁的区别

Question

ReaderWriterLock 类中的可升级读锁和写锁有什么区别？

根据MSDN的描述，只有一个线程可以进入可升级读锁。如果我遵循正确，我可以忘记升级它，因为它与写锁相同。有什么我想念的吗？

Answer 1

(我假设您指的是 ReaderWriterLockSlim，因为我认为 ReaderWriterLock 没有可升级的读取模式。)

虽然只有一个线程可以进入一个可升级读锁，但是一个线程可以有一个可升级读锁其他线程仍然可以进入一个读锁:

Only one thread can enter upgradeable mode at any given time. If a thread is in upgradeable mode, and there are no threads waiting to enter write mode, any number of other threads can enter read mode, even if there are threads waiting to enter upgradeable mode.

将其与写锁进行比较:

When there are threads waiting to enter write mode, additional threads that try to enter read mode or upgradeable mode block until all the threads waiting to enter write mode have either timed out or entered write mode and then exited from it.

换句话说，写锁是完全排他的，而可升级的读锁将允许其他线程继续进入/退出读取模式直到需要升级。