Explain the Readers-Writers problem and its solutions.

Multiple readers can read simultaneously (read-only, no conflicts), but writers need exclusive access. First readers-writers: readers preferred (writers may starve). Second: writers preferred (readers may starve). Fair solution: arrival-order access. Implementation uses semaphores/mutexes: read_count (readers currently reading), mutex (protects read_count), rw_mutex (write access). Reader: lock mutex, increment count, if first reader lock rw_mutex, unlock mutex, read, similar for exit.