Al Viro <v...@zeniv.linux.org.uk> wrote: > What's wrong with > p_occupancy = pipe_occupancy(head, tail); > if (p_occupancy >= pipe->max_usage) > return 0; > else > return pipe->max_usage - p_occupancy;
Because "pipe->max_usage - p_occupancy" can be negative. post_one_notification() is limited by pipe->ring_size, not pipe->max_usage. The idea is to allow some slack in a watch pipe for the watch_queue code to use that userspace can't. David
