If you use kqueue(), should you set O_NONBLOCK on your file descriptors? In other words, does kqueue() guarantee that the next I/O operation on a ready file descriptor will not block, regardless of whether O_NONBLOCK is set?
If you use kqueue(), should you set O_NONBLOCK on your file descriptors?
Nope.
In other words, does kqueue() guarantee that the next I/O operation on a ready file descriptor will not block, regardless of whether O_NONBLOCK is set?
Yep.
You do not need to. However, I generally do as a sanity check. This makes operations like read() return -1 and set errno to EWOULDBLOCK. I would much rather get an EWOULDBLOCK and know that my implementation of kqueue is buggy than have read() calls block (and therefore my program freeze) for unknown reasons.
来源：https://stackoverflow.com/questions/9755864/kqueue-and-o-nonblock