In the single-lock strategy, a thread acquires a single, application-wide mutex lock whenever any thread in the application is running and releases the lock before the thread blocks. The single-lock strategy requires cooperation from all modules and libraries in the system to synchronize on the single lock. Because only one thread can be accessing shared data at any given time, each thread has a consistent view of memory. This strategy is quite effective in a uniprocessor, provided shared memory is put into a consistent state before the lock is released and that the lock is released often enough to allow other threads to run. Furthermore, in uniprocessor systems, concurrency is diminished if the lock is not dropped during most I/O operations. The single-lock strategy cannot be applied in a multiprocessor system.