Fwd: libev doesn't notify on read event (file FD and timers)

[Assaf Inbal]

Hey all,

I'm using libev as a part of a larger project. In this project I have a
library that does some asynchronous work directly over FDs and timers.
While I understand that it's not exactly recommended, these FDs can also be
of local files as well as sockets.

As a part of the process, I have an EV_READ event set on a file, in that
handler I stop the event handler and close the FD. I then set a timer and
in that timer, open another file and set a read event on it.
The issue is that the read event on the second file is never called.
I've attached a sample code file to show this happening.
I'm using libev 4.11 on Ubuntu 12.04 LTS compiling with gcc as follows: gcc
ev_test.c -o ev_test -lev
I also tried to locally compile 4.15 but the issue reproduced there as well
(assuming I did so correctly).

It's worth mentioning that if I disable the timer and create the second
read event in the first's handler (undef USE_TIMER) everything works as
expected.
I also tried not closing the FD (commenting out line 36), thus making the
second file get a different FD, and that also worked.
Changing the timeout value from 0 to anything else didn't help.

Can anyone please tell me why this happens? Or, better yet, how I can fix
it?

Thanks,
Assaf

#include <stdlib.h>
#include <stdio.h>
#include <sys/fcntl.h>
#include <ev.h>

#define USE_TIMER
static ev_io io1, io2;
#ifdef USE_TIMER
static ev_timer timer1;
#endif
static char *file1 = "/bin/cp", *file2 = "/bin/mv";
static int fd1, fd2;

static void io2_cb(EV_P_ ev_io *w, int revents)
{
    printf("Got read event 2\n");
    ev_io_stop(EV_DEFAULT, w);
    close(fd2);
}

#ifdef USE_TIMER
static void timer1_cb(EV_P_ ev_timer *w, int revents)
{
    fd2 = open(file2, O_RDONLY | O_NONBLOCK);
    printf("%d\n", fd2);

    ev_io_init(&io2, io2_cb, fd2, EV_READ);
    ev_io_start(EV_DEFAULT, &io2);
}
#endif

static void io1_cb(EV_P_ ev_io *w, int revents)
{
    printf("Got read event 1\n");
    ev_io_stop(EV_DEFAULT, w);
    close(fd1);

#ifdef USE_TIMER
    ev_timer_init(&timer1, timer1_cb, 0., 0.);
    ev_timer_start(EV_DEFAULT, &timer1);
#else
    fd2 = open(file2, O_RDONLY | O_NONBLOCK);
    printf("%d\n", fd2);

    ev_io_init(&io2, io2_cb, fd2, EV_READ);
    ev_io_start(EV_DEFAULT, &io2);
#endif
}

int main (void)
{
    fd1 = open(file1, O_RDONLY | O_NONBLOCK);
    printf("%d\n", fd1);
    ev_io_init(&io1, io1_cb, fd1, EV_READ);
    ev_io_start(EV_DEFAULT, &io1);

    ev_loop(EV_DEFAULT, 0);
    return 0;
}

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