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authorSeongJae Park <sjpark@amazon.de>2020-12-14 10:07:13 +0100
committerJuergen Gross <jgross@suse.com>2020-12-14 10:07:13 +0100
commit3dc86ca6b4c8cfcba9da7996189d1b5a358a94fc (patch)
treef862850ffd2c042167390114c8b8e6354febce04 /drivers/xen/xenbus
parentbe987200fbaceaef340872841d4f7af2c5ee8dc3 (diff)
xen/xenbus: Count pending messages for each watch
This commit adds a counter of pending messages for each watch in the struct. It is used to skip unnecessary pending messages lookup in 'unregister_xenbus_watch()'. It could also be used in 'will_handle' callback. This is part of XSA-349 Cc: stable@vger.kernel.org Signed-off-by: SeongJae Park <sjpark@amazon.de> Reported-by: Michael Kurth <mku@amazon.de> Reported-by: Pawel Wieczorkiewicz <wipawel@amazon.de> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/xen/xenbus')
-rw-r--r--drivers/xen/xenbus/xenbus_xs.c29
1 files changed, 18 insertions, 11 deletions
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index e8bdbd0a1e26..12e02eb01f59 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -711,6 +711,7 @@ int xs_watch_msg(struct xs_watch_event *event)
event->path, event->token))) {
spin_lock(&watch_events_lock);
list_add_tail(&event->list, &watch_events);
+ event->handle->nr_pending++;
wake_up(&watch_events_waitq);
spin_unlock(&watch_events_lock);
} else
@@ -768,6 +769,8 @@ int register_xenbus_watch(struct xenbus_watch *watch)
sprintf(token, "%lX", (long)watch);
+ watch->nr_pending = 0;
+
down_read(&xs_watch_rwsem);
spin_lock(&watches_lock);
@@ -817,11 +820,14 @@ void unregister_xenbus_watch(struct xenbus_watch *watch)
/* Cancel pending watch events. */
spin_lock(&watch_events_lock);
- list_for_each_entry_safe(event, tmp, &watch_events, list) {
- if (event->handle != watch)
- continue;
- list_del(&event->list);
- kfree(event);
+ if (watch->nr_pending) {
+ list_for_each_entry_safe(event, tmp, &watch_events, list) {
+ if (event->handle != watch)
+ continue;
+ list_del(&event->list);
+ kfree(event);
+ }
+ watch->nr_pending = 0;
}
spin_unlock(&watch_events_lock);
@@ -868,7 +874,6 @@ void xs_suspend_cancel(void)
static int xenwatch_thread(void *unused)
{
- struct list_head *ent;
struct xs_watch_event *event;
xenwatch_pid = current->pid;
@@ -883,13 +888,15 @@ static int xenwatch_thread(void *unused)
mutex_lock(&xenwatch_mutex);
spin_lock(&watch_events_lock);
- ent = watch_events.next;
- if (ent != &watch_events)
- list_del(ent);
+ event = list_first_entry_or_null(&watch_events,
+ struct xs_watch_event, list);
+ if (event) {
+ list_del(&event->list);
+ event->handle->nr_pending--;
+ }
spin_unlock(&watch_events_lock);
- if (ent != &watch_events) {
- event = list_entry(ent, struct xs_watch_event, list);
+ if (event) {
event->handle->callback(event->handle, event->path,
event->token);
kfree(event);