Not mentioned: “Open file description locks” (https://man7.org/linux/man-pages/man2/fcntl.2.html https://man7.org/linux/man-pages/man2/fcntl.2.html), which are

Not mentioned: “Open file description locks” (https://man7.org/linux/man-pages/man2/fcntl.2.html https://man7.org/linux/man-pages/man2/fcntl.2.html), which are the locks you usually actually want.