Well, just by looking at a glance, kqueue seems to pose similar problems. I mean, the problem mentioned in the OP:

  1. Kernel receives some data, and wakes up A
  2. A reads some data
  3. Kernel receives some other data, and wakes up B (cause A didn't call `epoll_wait` yet)
  4. B reads some data, leading to a race condition (out-of-order reading).

kqueue's `kevent` seems to be more or less similar to `epoll_wait`, in that it doesn't seem to provide a way to notify the kernel the "we're done" signal. Am I missing here? Does `kevent` also signal the end of the exclusive access?