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


From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH] [RFC] Add glib support to main loop
Date: Wed, 27 Jul 2011 15:48:25 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110516 Lightning/1.0b2 Thunderbird/3.1.10

On 07/27/2011 03:43 PM, Blue Swirl wrote:
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?

Oh, this is just me being lazy. There's a way to do this without using the assert. I put the assert there to make sure that I didn't leave a latent bug.

But in general, I don't think we should ever define NDEBUG.

+
+    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.

They are in the code below :-)

  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();

Regards,

Anthony Liguori

--
1.7.4.1







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