All program locks are listed below.  Also the order shown is also
locking order.  That is if you need to hold more than one lock, you may
only grab them in the order shown.

A lock is necessary to obtain for any access (read or write) of the
rest of the structure, unless otherwise noted.  Also, access to the lock
itself does not require a lock beforehand.  And condition variables
(which are within the structure) also do not need a lock obtained
beforehand.

state_info.lock

display_info.lock   As above, and any call to ncurses (such as
                    getch() or wgetyx() ).

database_info.lock  As above, note this is a read/write lock
                    instead of a regular mutex.

song_queue.lock

past_queue.lock

player_info.lock

player_command.lock

frame_buffer.lock

spectrum_info.lock

spectrum_ring.lock

log_info.lock       You do not need to use this lock.  It is
                    only used by the internal _squash_error() and
                    _squash_log() functions.  Use the squash_error()
                    and squash_log() macros instead.

status_info.lock    You do not need to use this lock.  It is
                    only used by the main() and internal _squash_error()
                    functions.  Use the squash_error() macro instead.