edge triggered illumos bug

main.c

#include <err.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>

void write_to_event_fd(int event_fd) {
        static uint64_t data = 1;

        if (write(event_fd, &data, sizeof (data)) != sizeof (data)) {
                err(1, "write to event_fd");
        }
}

void read_from_event_fd(int event_fd) {
        static uint64_t want_data = 1;
        uint64_t have_data;

        if (read(event_fd, &have_data, sizeof (have_data)) != sizeof (have_data)) {
                err(1, "read from event_fd");
        }

        if (want_data != have_data) {
                err(1, "read bad data from event_fd");
        }
}

void wait_for_epoll_events(int epoll_fd) {
        int nevents = 50;
        int timeout = -1;
        struct epoll_event ep_events[nevents];
        int num_events;

        num_events = epoll_wait(epoll_fd, ep_events, nevents, timeout);

        if (num_events != 1) {
                err(1, "epoll_wait returned bad value: %d", num_events);
        }
}

int main(int arg, char **argv) {
        int ret;
        struct epoll_event ev;

        // create epoll handle
        int epoll_fd = epoll_create1(EPOLL_CLOEXEC);
        if (epoll_fd == -1) {
                err(1, "epoll_create1");
        }

        int pipe_fds[2];
        if (pipe(pipe_fds) == -1) {
                err(1, "pipe");
        }
        if (fcntl(pipe_fds[0], F_SETFL, O_NONBLOCK) == -1) {
                err(3, "set read end nonblocking");
        }
        if (fcntl(pipe_fds[1], F_SETFL, O_NONBLOCK) == -1) {
                err(3, "set write end nonblocking");
        }

        // add eventfd handle to epoll event watcher
        ev.events = EPOLLIN | EPOLLRDHUP | EPOLLET;
        ev.data.ptr = NULL;
        ret = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, pipe_fds[0], &ev);
        if (ret == -1) {
                err(1, "epoll_ctl (add pipe to epoll)");
        }

        printf("writing to pipe...\n");
        write_to_event_fd(pipe_fds[1]);
        printf("waiting for epoll...\n");
        wait_for_epoll_events(epoll_fd);
        printf("first epoll_wait returned\n");
        /*
         * If we skip the read on Linux the edge triggered event
         * still causes epoll_wait to return.  On illumos this isn't
         * the case
         */
        //read_from_event_fd(pipe_fds[0]);
        printf("writing to pipe...\n");
        write_to_event_fd(pipe_fds[1]);
        printf("waiting for epoll...\n");
        wait_for_epoll_events(epoll_fd);
        printf("second epoll_wait returned\n");

        return 0;
}