Java并发编程

Question

Is the lock retained by the thread when context switch occur. When we invoke a wait() the locks are given up by thread, what happens when theres a context switch.

Thanks

Answer 1

Yes, locks are retained during a context switch. In fact, that's the whole point of a lock.

When a thread calls wait it relinquishes the lock. When wait returns the lock is re-obtained, so you can guarantee that when control returns to your thread it holds all the locks you expect.

Answer 2

The thread that invoked wait() gets suspended until some other thread invokes notify*() on the object. At that point, when another context switch occurs, the wait() call will return and the waiting thread will immediately try to re-acquire the lock before proceeding further.