Re: [Qemu-devel] [5633] Fix alarm_timer race with select - v3 (Jan Kiszka)

[Anthony Liguori <anthony@codemonkey.ws>]

> @@ -1674,7 +1678,21 @@
>  {
>      struct qemu_alarm_timer *t = NULL;
>      int i, err = -1;
> +    int fds[2];
>  
> +    if (pipe(fds) < 0) {
> +    fail:
> +        perror("creating timer pipe");
> +        exit(1);
> +    }
>   

pipe() doesn't exist on Windows apparently.  I'm open to suggestions on 
how to fix this properly.  host_alarm_handler isn't a signal handler on 
Windows so perhaps we can just not to the pipe trickery on Windows.

Thoughts?

Regards,

Anthony Liguori

> +    for (i = 0; i < 2; i++) {
> +        int flags = fcntl(fds[i], F_GETFL);
> +        if (flags == -1 || fcntl(fds[i], F_SETFL, flags | O_NONBLOCK))
> +            goto fail;
> +    }
> +    alarm_timer_rfd = fds[0];
> +    alarm_timer_wfd = fds[1];
> +
>      for (i = 0; alarm_timers[i].name; i++) {
>          t = &alarm_timers[i];
>  
> @@ -4426,8 +4444,9 @@
>  
>      /* poll any events */
>      /* XXX: separate device handlers from system ones */
> -    nfds = -1;
> +    nfds = alarm_timer_rfd;
>      FD_ZERO(&rfds);
> +    FD_SET(alarm_timer_rfd, &rfds);
>      FD_ZERO(&wfds);
>      FD_ZERO(&xfds);
>      for(ioh = first_io_handler; ioh != NULL; ioh = ioh->next) {
> @@ -4501,6 +4520,11 @@
>                      qemu_get_clock(rt_clock));
>  
>      if (alarm_timer->flags & ALARM_FLAG_EXPIRED) {
> +        char byte;
> +        do {
> +            ret = read(alarm_timer_rfd, &byte, sizeof(byte));
> +        } while (ret != -1 || errno != EAGAIN);
> +
>          alarm_timer->flags &= ~(ALARM_FLAG_EXPIRED);
>          qemu_rearm_alarm_timer(alarm_timer);
>      }
>
>
>
>
>