xen / notify: introduce a new XenWatchList abstraction
Xenstore watch call-backs are already abstracted away from XenBus using
the XenWatch data structure but the associated NotifierList manipulation
and file handle registration is still open coded in various xen_bus_...()
functions.
This patch creates a new XenWatchList data structure to allow these
interactions to be abstracted away from XenBus as well. This is in
preparation for a subsequent patch which will introduce separate watch lists
for XenBus and XenDevice objects.
NOTE: This patch also introduces a new notifier_list_empty() helper function
for the purposes of adding an assertion that a XenWatchList is not
freed whilst its associated NotifierList is still occupied.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony Perard <anthony.perard@citrix.com>
Message-Id: <20190913082159.31338-2-paul.durrant@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index 025df5e..28efacc 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -157,18 +157,60 @@
g_free(watch);
}
-static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node,
- const char *key, XenWatchHandler handler,
- void *opaque, Error **errp)
+struct XenWatchList {
+ struct xs_handle *xsh;
+ NotifierList notifiers;
+};
+
+static void watch_list_event(void *opaque)
+{
+ XenWatchList *watch_list = opaque;
+ char **v;
+ const char *token;
+
+ v = xs_check_watch(watch_list->xsh);
+ if (!v) {
+ return;
+ }
+
+ token = v[XS_WATCH_TOKEN];
+
+ notifier_list_notify(&watch_list->notifiers, (void *)token);
+
+ free(v);
+}
+
+static XenWatchList *watch_list_create(struct xs_handle *xsh)
+{
+ XenWatchList *watch_list = g_new0(XenWatchList, 1);
+
+ g_assert(xsh);
+
+ watch_list->xsh = xsh;
+ notifier_list_init(&watch_list->notifiers);
+ qemu_set_fd_handler(xs_fileno(watch_list->xsh), watch_list_event, NULL,
+ watch_list);
+
+ return watch_list;
+}
+
+static void watch_list_destroy(XenWatchList *watch_list)
+{
+ g_assert(notifier_list_empty(&watch_list->notifiers));
+ qemu_set_fd_handler(xs_fileno(watch_list->xsh), NULL, NULL, NULL);
+ g_free(watch_list);
+}
+
+static XenWatch *watch_list_add(XenWatchList *watch_list, const char *node,
+ const char *key, XenWatchHandler handler,
+ void *opaque, Error **errp)
{
XenWatch *watch = new_watch(node, key, handler, opaque);
Error *local_err = NULL;
- trace_xen_bus_add_watch(watch->node, watch->key, watch->token);
+ notifier_list_add(&watch_list->notifiers, &watch->notifier);
- notifier_list_add(&xenbus->watch_notifiers, &watch->notifier);
-
- xs_node_watch(xenbus->xsh, node, key, watch->token, &local_err);
+ xs_node_watch(watch_list->xsh, node, key, watch->token, &local_err);
if (local_err) {
error_propagate(errp, local_err);
@@ -181,18 +223,34 @@
return watch;
}
-static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch,
- Error **errp)
+static void watch_list_remove(XenWatchList *watch_list, XenWatch *watch,
+ Error **errp)
{
- trace_xen_bus_remove_watch(watch->node, watch->key, watch->token);
-
- xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch->token,
+ xs_node_unwatch(watch_list->xsh, watch->node, watch->key, watch->token,
errp);
notifier_remove(&watch->notifier);
free_watch(watch);
}
+static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node,
+ const char *key, XenWatchHandler handler,
+ void *opaque, Error **errp)
+{
+ trace_xen_bus_add_watch(node, key);
+
+ return watch_list_add(xenbus->watch_list, node, key, handler, opaque,
+ errp);
+}
+
+static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch,
+ Error **errp)
+{
+ trace_xen_bus_remove_watch(watch->node, watch->key);
+
+ watch_list_remove(xenbus->watch_list, watch, errp);
+}
+
static void xen_bus_backend_create(XenBus *xenbus, const char *type,
const char *name, char *path,
Error **errp)
@@ -338,35 +396,14 @@
xenbus->backend_watch = NULL;
}
- if (!xenbus->xsh) {
- return;
+ if (xenbus->watch_list) {
+ watch_list_destroy(xenbus->watch_list);
+ xenbus->watch_list = NULL;
}
- qemu_set_fd_handler(xs_fileno(xenbus->xsh), NULL, NULL, NULL);
-
- xs_close(xenbus->xsh);
-}
-
-static void xen_bus_watch(void *opaque)
-{
- XenBus *xenbus = opaque;
- char **v;
- const char *token;
-
- g_assert(xenbus->xsh);
-
- v = xs_check_watch(xenbus->xsh);
- if (!v) {
- return;
+ if (xenbus->xsh) {
+ xs_close(xenbus->xsh);
}
-
- token = v[XS_WATCH_TOKEN];
-
- trace_xen_bus_watch(token);
-
- notifier_list_notify(&xenbus->watch_notifiers, (void *)token);
-
- free(v);
}
static void xen_bus_realize(BusState *bus, Error **errp)
@@ -390,9 +427,7 @@
xenbus->backend_id = 0; /* Assume lack of node means dom0 */
}
- notifier_list_init(&xenbus->watch_notifiers);
- qemu_set_fd_handler(xs_fileno(xenbus->xsh), xen_bus_watch, NULL,
- xenbus);
+ xenbus->watch_list = watch_list_create(xenbus->xsh);
module_call_init(MODULE_INIT_XEN_BACKEND);
