Obtain a write lock on @rw_lock. If any thread already holds a read or write lock on @rw_lock, the current thread will block until all other threads have dropped their locks on @rw_lock.
2.32
See Implementation
Obtain a write lock on @rw_lock. If any thread already holds a read or write lock on @rw_lock, the current thread will block until all other threads have dropped their locks on @rw_lock.