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xen / notify: introduce a new XenWatchList abstraction

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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>
This commit is contained in:
Paul Durrant 2019-09-13 09:21:56 +01:00 • committed by Anthony PERARD
parent df6180bb56
commit 374752a26b
5 changed files with 87 additions and 45 deletions
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117
hw/xen/xen-bus.c
View file

@ -157,18 +157,60 @@ static void free_watch(XenWatch *watch)
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 @@ static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node,
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 @@ static void xen_bus_unrealize(BusState *bus, Error **errp)
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 @@ static void xen_bus_realize(BusState *bus, Error **errp)
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);