This bug can be triggered by the following series of events:
A acquires a write lock
B starts waiting for a read lock
C starts waiting for a read lock
A releases the write lock
After this, both B and C are supposed to be resumed as a read-lock is available.
However, with the previous implementation, only C would be resumed immediately.
Other goroutines could immediately acquire the read lock, but B would not be resumed until C released the read lock.
