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. Since 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. Since 2.32