Re: [Qemu-devel] [PATCH] [RFC] Add glib support to main loop

[Blue Swirl]

On Wed, Jul 27, 2011 at 3:06 AM, Anthony Liguori <address@hidden> wrote:
> This allows GSources to be used to register callback events in QEMU.  This is
> useful as it allows us to take greater advantage of glib and also because it
> allows us to write code that is more easily testable outside of QEMU since we
> can make use of glib's main loop in unit tests.
>
> All new code should use glib's callback mechanisms for registering fd events
> which are very well documented at:
>
> http://developer.gnome.org/glib/stable/glib-The-Main-Event-Loop.html
>
> And:
>
> http://developer.gnome.org/gio/stable/
>
> Signed-off-by: Anthony Liguori <address@hidden>
> ---
>  vl.c |   74 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 74 insertions(+), 0 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 4b6688b..19774ac 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -111,6 +111,8 @@ int main(int argc, char **argv)
>  #define main qemu_main
>  #endif /* CONFIG_COCOA */
>
> +#include <glib.h>
> +
>  #include "hw/hw.h"
>  #include "hw/boards.h"
>  #include "hw/usb.h"
> @@ -1309,6 +1311,75 @@ void qemu_system_vmstop_request(int reason)
>     qemu_notify_event();
>  }
>
> +static GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
> +static int n_poll_fds;
> +static int max_priority;
> +
> +static void glib_select_fill(int *max_fd, fd_set *rfds, fd_set *wfds,
> +                             fd_set *xfds, struct timeval *tv)
> +{
> +    GMainContext *context = g_main_context_default();
> +    int i;
> +    int timeout = 0, cur_timeout;
> +
> +    g_main_context_prepare(context, &max_priority);
> +
> +    n_poll_fds = g_main_context_query(context, max_priority, &timeout,
> +                                      poll_fds, ARRAY_SIZE(poll_fds));
> +    g_assert(n_poll_fds <= ARRAY_SIZE(poll_fds));

The use of g_assert() means that production code should define
G_DISABLE_ASSERT in addition to NDEBUG. Should we make both default
for stable versions?

> +
> +    for (i = 0; i < n_poll_fds; i++) {
> +        GPollFD *p = &poll_fds[i];
> +
> +        if ((p->events & G_IO_IN)) {
> +            FD_SET(p->fd, rfds);
> +            *max_fd = MAX(*max_fd, p->fd);
> +        }
> +        if ((p->events & G_IO_OUT)) {
> +            FD_SET(p->fd, wfds);
> +            *max_fd = MAX(*max_fd, p->fd);
> +        }
> +        if ((p->events & G_IO_ERR)) {
> +            FD_SET(p->fd, xfds);
> +            *max_fd = MAX(*max_fd, p->fd);
> +        }
> +    }
> +
> +    cur_timeout = (tv->tv_sec * 1000) + ((tv->tv_usec + 500) / 1000);
> +    if (timeout >= 0 && timeout < cur_timeout) {
> +        tv->tv_sec = timeout / 1000;
> +        tv->tv_usec = (timeout % 1000) * 1000;
> +    }
> +}
> +
> +static void glib_select_poll(fd_set *rfds, fd_set *wfds, fd_set *xfds,
> +                             bool err)
> +{
> +    GMainContext *context = g_main_context_default();
> +
> +    if (!err) {
> +        int i;
> +
> +        for (i = 0; i < n_poll_fds; i++) {
> +            GPollFD *p = &poll_fds[i];
> +
> +            if ((p->events & G_IO_IN) && FD_ISSET(p->fd, rfds)) {
> +                p->revents |= G_IO_IN;
> +            }
> +            if ((p->events & G_IO_OUT) && FD_ISSET(p->fd, wfds)) {
> +                p->revents |= G_IO_OUT;
> +            }
> +            if ((p->events & G_IO_ERR) && FD_ISSET(p->fd, xfds)) {
> +                p->revents |= G_IO_ERR;
> +            }
> +        }
> +    }
> +
> +    if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
> +        g_main_context_dispatch(context);
> +    }
> +}
> +

The above functions do not seem to be referenced anywhere.

>  void main_loop_wait(int nonblocking)
>  {
>     fd_set rfds, wfds, xfds;
> @@ -1334,8 +1405,10 @@ void main_loop_wait(int nonblocking)
>     FD_ZERO(&rfds);
>     FD_ZERO(&wfds);
>     FD_ZERO(&xfds);
> +
>     qemu_iohandler_fill(&nfds, &rfds, &wfds, &xfds);
>     slirp_select_fill(&nfds, &rfds, &wfds, &xfds);
> +    glib_select_fill(&nfds, &rfds, &wfds, &xfds, &tv);
>
>     qemu_mutex_unlock_iothread();
>     ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv);
> @@ -1343,6 +1416,7 @@ void main_loop_wait(int nonblocking)
>
>     qemu_iohandler_poll(&rfds, &wfds, &xfds, ret);
>     slirp_select_poll(&rfds, &wfds, &xfds, (ret < 0));
> +    glib_select_poll(&rfds, &wfds, &xfds, (ret < 0));
>
>     qemu_run_all_timers();
>
> --
> 1.7.4.1
>
>
>