util: import an event loop impl based on GMainContext

The libvirt-glib project has provided a GMainContext based
event loop impl for applications. This imports it and sets
it up for use by libvirt as the primary event loop. This
remains a private impl detail of libvirt.

IOW, applications must *NOT* assume that a call to
"virEventRegisterDefaultImpl" results in a GLib based
event loop. They should continue to use the libvirt-glib
API gvir_event_register() if they explicitly want to
guarantee a GLib event loop.

This follows the general principle that the libvirt public
API should not expose the fact that GLib is being used
internally.

Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

build-aux/syntax-check.mk

@@ -2176,7 +2176,7 @@ exclude_file_name_regexp--sc_avoid_write = \
 
 exclude_file_name_regexp--sc_bindtextdomain = .*
 
-exclude_file_name_regexp--sc_gettext_init = ^((tests|examples)/|tools/virt-login-shell.c)
+exclude_file_name_regexp--sc_gettext_init = ^((tests|examples)/|tools/virt-login-shell.c|src/util/vireventglib\.c)
 
 exclude_file_name_regexp--sc_copyright_format = \
 	^build-aux/syntax-check\.mk$$

src/libvirt_private.syms

@@ -1933,6 +1933,11 @@ virSetErrorLogPriorityFunc;
 virStrerror;
 
 
+# util/vireventglib.h
+virEventGLibRegister;
+virEventGLibRunOnce;
+
+
 # util/vireventpoll.h
 virEventPollAddHandle;
 virEventPollAddTimeout;

src/libvirt_probes.d

@@ -15,6 +15,20 @@ provider libvirt {
 
 	probe event_poll_run(int nfds, int timeout);
 
+	# file: src/util/vireventglib.c
+	# prefix: event_glib
+	probe event_glib_add_handle(int watch, int fd, int events, void *cb, void *opaque, void *ff);
+	probe event_glib_update_handle(int watch, int events);
+	probe event_glib_remove_handle(int watch);
+	probe event_glib_remove_handle_idle(int watch, void *ff, void *opaque);
+	probe event_glib_dispatch_handle(int watch, int events, void *cb, void *opaque);
+
+	probe event_glib_add_timeout(int timer, int frequency, void *cb, void *opaque, void *ff);
+	probe event_glib_update_timeout(int timer, int frequency);
+	probe event_glib_remove_timeout(int timer);
+	probe event_glib_remove_timeout_idle(int timer, void *ff, void *opaque);
+	probe event_glib_dispatch_timeout(int timer, void *cb, void *opaque);
+
 	# file: src/util/virdbus.c
 	# prefix: dbus
 	probe dbus_method_call(const char *interface, const char *member, const char *object, const char *destination);

src/util/Makefile.inc.am

@@ -61,6 +61,8 @@ UTIL_SOURCES = \
 	util/virerrorpriv.h \
 	util/virevent.c \
 	util/virevent.h \
+	util/vireventglib.c \
+	util/vireventglib.h \
 	util/vireventglibwatch.c \
 	util/vireventglibwatch.h \
 	util/vireventpoll.c \

src/util/vireventglib.c

@@ -0,0 +1,499 @@
+/*
+ * vireventglib.c: GMainContext based event loop
+ *
+ * Copyright (C) 2008 Daniel P. Berrange
+ * Copyright (C) 2010-2019 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "vireventglib.h"
+#include "vireventglibwatch.h"
+#include "virerror.h"
+#include "virlog.h"
+#include "virprobe.h"
+
+#ifdef G_OS_WIN32
+# include <io.h>
+#endif
+
+#define VIR_FROM_THIS VIR_FROM_EVENT
+
+VIR_LOG_INIT("util.eventglib");
+
+struct virEventGLibHandle
+{
+    int watch;
+    int fd;
+    int events;
+    int removed;
+    guint source;
+    virEventHandleCallback cb;
+    void *opaque;
+    virFreeCallback ff;
+};
+
+struct virEventGLibTimeout
+{
+    int timer;
+    int interval;
+    int removed;
+    guint source;
+    virEventTimeoutCallback cb;
+    void *opaque;
+    virFreeCallback ff;
+};
+
+static GMutex *eventlock;
+
+static int nextwatch = 1;
+static GPtrArray *handles;
+
+static int nexttimer = 1;
+static GPtrArray *timeouts;
+
+static GIOCondition
+virEventGLibEventsToCondition(int events)
+{
+    GIOCondition cond = 0;
+    if (events & VIR_EVENT_HANDLE_READABLE)
+        cond |= G_IO_IN;
+    if (events & VIR_EVENT_HANDLE_WRITABLE)
+        cond |= G_IO_OUT;
+    if (events & VIR_EVENT_HANDLE_ERROR)
+        cond |= G_IO_ERR;
+    if (events & VIR_EVENT_HANDLE_HANGUP)
+        cond |= G_IO_HUP;
+    return cond;
+}
+
+static int
+virEventGLibConditionToEvents(GIOCondition cond)
+{
+    int events = 0;
+    if (cond & G_IO_IN)
+        events |= VIR_EVENT_HANDLE_READABLE;
+    if (cond & G_IO_OUT)
+        events |= VIR_EVENT_HANDLE_WRITABLE;
+    if (cond & G_IO_ERR)
+        events |= VIR_EVENT_HANDLE_ERROR;
+    if (cond & G_IO_NVAL) /* Treat NVAL as error, since libvirt doesn't distinguish */
+        events |= VIR_EVENT_HANDLE_ERROR;
+    if (cond & G_IO_HUP)
+        events |= VIR_EVENT_HANDLE_HANGUP;
+    return events;
+}
+
+static gboolean
+virEventGLibHandleDispatch(int fd G_GNUC_UNUSED,
+                           GIOCondition condition,
+                           gpointer opaque)
+{
+    struct virEventGLibHandle *data = opaque;
+    int events = virEventGLibConditionToEvents(condition);
+
+    VIR_DEBUG("Dispatch handler data=%p watch=%d fd=%d events=%d opaque=%p",
+              data, data->watch, data->fd, events, data->opaque);
+
+    PROBE(EVENT_GLIB_DISPATCH_HANDLE,
+          "watch=%d events=%d cb=%p opaque=%p",
+          data->watch, events, data->cb, data->opaque);
+
+    (data->cb)(data->watch, data->fd, events, data->opaque);
+
+    return TRUE;
+}
+
+
+static int
+virEventGLibHandleAdd(int fd,
+                      int events,
+                      virEventHandleCallback cb,
+                      void *opaque,
+                      virFreeCallback ff)
+{
+    struct virEventGLibHandle *data;
+    GIOCondition cond = virEventGLibEventsToCondition(events);
+    int ret;
+
+    g_mutex_lock(eventlock);
+
+    data = g_new0(struct virEventGLibHandle, 1);
+
+    data->watch = nextwatch++;
+    data->fd = fd;
+    data->events = events;
+    data->cb = cb;
+    data->opaque = opaque;
+    data->ff = ff;
+
+    VIR_DEBUG("Add handle data=%p watch=%d fd=%d events=%d opaque=%p",
+              data, data->watch, data->fd, events, data->opaque);
+
+    if (events != 0) {
+        data->source = virEventGLibAddSocketWatch(
+            fd, cond, NULL, virEventGLibHandleDispatch, data, NULL);
+    }
+
+    g_ptr_array_add(handles, data);
+
+    ret = data->watch;
+
+    PROBE(EVENT_GLIB_ADD_HANDLE,
+          "watch=%d fd=%d events=%d cb=%p opaque=%p ff=%p",
+          ret, fd, events, cb, opaque, ff);
+    g_mutex_unlock(eventlock);
+
+    return ret;
+}
+
+static struct virEventGLibHandle *
+virEventGLibHandleFind(int watch)
+{
+    guint i;
+
+    for (i = 0; i < handles->len; i++) {
+        struct virEventGLibHandle *h = g_ptr_array_index(handles, i);
+
+        if (h == NULL) {
+            g_warn_if_reached();
+            continue;
+        }
+
+        if ((h->watch == watch) && !h->removed)
+            return h;
+    }
+
+    return NULL;
+}
+
+static void
+virEventGLibHandleUpdate(int watch,
+                         int events)
+{
+    struct virEventGLibHandle *data;
+
+    PROBE(EVENT_GLIB_UPDATE_HANDLE,
+          "watch=%d events=%d",
+          watch, events);
+    g_mutex_lock(eventlock);
+
+    data = virEventGLibHandleFind(watch);
+    if (!data) {
+        VIR_DEBUG("Update for missing handle watch=%d", watch);
+        goto cleanup;
+    }
+
+    VIR_DEBUG("Update handle data=%p watch=%d fd=%d events=%d",
+              data, watch, data->fd, events);
+
+    if (events != 0) {
+        GIOCondition cond = virEventGLibEventsToCondition(events);
+        if (events == data->events)
+            goto cleanup;
+
+        if (data->source != 0) {
+            VIR_DEBUG("Removed old handle watch=%d", data->source);
+            g_source_remove(data->source);
+        }
+
+        data->source = virEventGLibAddSocketWatch(
+            data->fd, cond, NULL, virEventGLibHandleDispatch, data, NULL);
+
+        data->events = events;
+        VIR_DEBUG("Added new handle watch=%d", data->source);
+    } else {
+        if (data->source == 0)
+            goto cleanup;
+
+        VIR_DEBUG("Removed old handle watch=%d", data->source);
+        g_source_remove(data->source);
+        data->source = 0;
+        data->events = 0;
+    }
+
+ cleanup:
+    g_mutex_unlock(eventlock);
+}
+
+static gboolean
+virEventGLibHandleRemoveIdle(gpointer data)
+{
+    struct virEventGLibHandle *h = data;
+
+    PROBE(EVENT_GLIB_REMOVE_HANDLE_IDLE,
+          "watch=%d ff=%p opaque=%p",
+          h->watch, h->ff, h->opaque);
+    if (h->ff)
+        (h->ff)(h->opaque);
+
+    g_mutex_lock(eventlock);
+    g_ptr_array_remove_fast(handles, h);
+    g_mutex_unlock(eventlock);
+
+    return FALSE;
+}
+
+static int
+virEventGLibHandleRemove(int watch)
+{
+    struct virEventGLibHandle *data;
+    int ret = -1;
+
+    PROBE(EVENT_GLIB_REMOVE_HANDLE,
+          "watch=%d",
+          watch);
+    g_mutex_lock(eventlock);
+
+    data = virEventGLibHandleFind(watch);
+    if (!data) {
+        VIR_DEBUG("Remove of missing handle watch=%d", watch);
+        goto cleanup;
+    }
+
+    VIR_DEBUG("Remove handle data=%p watch=%d fd=%d",
+              data, watch, data->fd);
+
+    if (data->source != 0) {
+        g_source_remove(data->source);
+        data->source = 0;
+        data->events = 0;
+    }
+
+    /* since the actual watch deletion is done asynchronously, a handleUpdate call may
+     * reschedule the watch before it's fully deleted, that's why we need to mark it as
+     * 'removed' to prevent reuse
+     */
+    data->removed = TRUE;
+    g_idle_add(virEventGLibHandleRemoveIdle, data);
+
+    ret = 0;
+
+ cleanup:
+    g_mutex_unlock(eventlock);
+    return ret;
+}
+
+
+static gboolean
+virEventGLibTimeoutDispatch(void *opaque)
+{
+    struct virEventGLibTimeout *data = opaque;
+
+    VIR_DEBUG("Dispatch timeout data=%p cb=%p timer=%d opaque=%p",
+              data, data->cb, data->timer, data->opaque);
+
+    PROBE(EVENT_GLIB_DISPATCH_TIMEOUT,
+          "timer=%d cb=%p opaque=%p",
+          data->timer, data->cb, data->opaque);
+    (data->cb)(data->timer, data->opaque);
+
+    return TRUE;
+}
+
+static int
+virEventGLibTimeoutAdd(int interval,
+                       virEventTimeoutCallback cb,
+                       void *opaque,
+                       virFreeCallback ff)
+{
+    struct virEventGLibTimeout *data;
+    int ret;
+
+    g_mutex_lock(eventlock);
+
+    data = g_new0(struct virEventGLibTimeout, 1);
+    data->timer = nexttimer++;
+    data->interval = interval;
+    data->cb = cb;
+    data->opaque = opaque;
+    data->ff = ff;
+    if (interval >= 0)
+        data->source = g_timeout_add(interval,
+                                     virEventGLibTimeoutDispatch,
+                                     data);
+
+    g_ptr_array_add(timeouts, data);
+
+    VIR_DEBUG("Add timeout data=%p interval=%d ms cb=%p opaque=%p timer=%d",
+              data, interval, cb, opaque, data->timer);
+
+    ret = data->timer;
+
+    PROBE(EVENT_GLIB_ADD_TIMEOUT,
+          "timer=%d interval=%d cb=%p opaque=%p ff=%p",
+          ret, interval, cb, opaque, ff);
+    g_mutex_unlock(eventlock);
+
+    return ret;
+}
+
+
+static struct virEventGLibTimeout *
+virEventGLibTimeoutFind(int timer)
+{
+    guint i;
+
+    g_return_val_if_fail(timeouts != NULL, NULL);
+
+    for (i = 0; i < timeouts->len; i++) {
+        struct virEventGLibTimeout *t = g_ptr_array_index(timeouts, i);
+
+        if (t == NULL) {
+            g_warn_if_reached();
+            continue;
+        }
+
+        if ((t->timer == timer) && !t->removed)
+            return t;
+    }
+
+    return NULL;
+}
+
+
+static void
+virEventGLibTimeoutUpdate(int timer,
+                          int interval)
+{
+    struct virEventGLibTimeout *data;
+
+    PROBE(EVENT_GLIB_UPDATE_TIMEOUT,
+          "timer=%d interval=%d",
+          timer, interval);
+    g_mutex_lock(eventlock);
+
+    data = virEventGLibTimeoutFind(timer);
+    if (!data) {
+        VIR_DEBUG("Update of missing timeout timer=%d", timer);
+        goto cleanup;
+    }
+
+    VIR_DEBUG("Update timeout data=%p timer=%d interval=%d ms", data, timer, interval);
+
+    if (interval >= 0) {
+        if (data->source != 0)
+            g_source_remove(data->source);
+
+        data->interval = interval;
+        data->source = g_timeout_add(data->interval,
+                                     virEventGLibTimeoutDispatch,
+                                     data);
+    } else {
+        if (data->source == 0)
+            goto cleanup;
+
+        g_source_remove(data->source);
+        data->source = 0;
+    }
+
+ cleanup:
+    g_mutex_unlock(eventlock);
+}
+
+static gboolean
+virEventGLibTimeoutRemoveIdle(gpointer data)
+{
+    struct virEventGLibTimeout *t = data;
+
+    PROBE(EVENT_GLIB_REMOVE_TIMEOUT_IDLE,
+          "timer=%d ff=%p opaque=%p",
+          t->timer, t->ff, t->opaque);
+
+    if (t->ff)
+        (t->ff)(t->opaque);
+
+    g_mutex_lock(eventlock);
+    g_ptr_array_remove_fast(timeouts, t);
+    g_mutex_unlock(eventlock);
+
+    return FALSE;
+}
+
+static int
+virEventGLibTimeoutRemove(int timer)
+{
+    struct virEventGLibTimeout *data;
+    int ret = -1;
+
+    PROBE(EVENT_GLIB_REMOVE_TIMEOUT,
+          "timer=%d",
+          timer);
+    g_mutex_lock(eventlock);
+
+    data = virEventGLibTimeoutFind(timer);
+    if (!data) {
+        VIR_DEBUG("Remove of missing timeout timer=%d", timer);
+        goto cleanup;
+    }
+
+    VIR_DEBUG("Remove timeout data=%p timer=%d",
+              data, timer);
+
+    if (data->source != 0) {
+        g_source_remove(data->source);
+        data->source = 0;
+    }
+
+    /* since the actual timeout deletion is done asynchronously, a timeoutUpdate call may
+     * reschedule the timeout before it's fully deleted, that's why we need to mark it as
+     * 'removed' to prevent reuse
+     */
+    data->removed = TRUE;
+    g_idle_add(virEventGLibTimeoutRemoveIdle, data);
+
+    ret = 0;
+
+ cleanup:
+    g_mutex_unlock(eventlock);
+    return ret;
+}
+
+
+static gpointer virEventGLibRegisterOnce(gpointer data G_GNUC_UNUSED)
+{
+    eventlock = g_new0(GMutex, 1);
+    timeouts = g_ptr_array_new_with_free_func(g_free);
+    handles = g_ptr_array_new_with_free_func(g_free);
+    virEventRegisterImpl(virEventGLibHandleAdd,
+                         virEventGLibHandleUpdate,
+                         virEventGLibHandleRemove,
+                         virEventGLibTimeoutAdd,
+                         virEventGLibTimeoutUpdate,
+                         virEventGLibTimeoutRemove);
+    return NULL;
+}
+
+
+void virEventGLibRegister(void)
+{
+    static GOnce once = G_ONCE_INIT;
+
+    g_once(&once, virEventGLibRegisterOnce, NULL);
+}
+
+
+int virEventGLibRunOnce(void)
+{
+    g_main_context_iteration(NULL, TRUE);
+
+    return 0;
+}

src/util/vireventglib.h

@@ -0,0 +1,28 @@
+/*
+ * vireventglib.h: GMainContext based event loop
+ *
+ * Copyright (C) 2008 Daniel P. Berrange
+ * Copyright (C) 2010-2019 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "internal.h"
+
+void virEventGLibRegister(void);
+
+int virEventGLibRunOnce(void);