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Subject[PATCH 3/6] xenbus: dispatch per-domU watch event to per-domU xenwatch thread
Date
This is the 3rd patch of a (6-patch) patch set.

This patch dispatches the watch event to per-domU xenwatch thread when the
event meets all of below conditions:

1. The watch is registered to use xenwatch multithreading feature and the
get_domid() method returns valid domid.
2. There is xenwatch thread (mtwatch domain) available for the domid
obtained from get_domid() method.
3. The xenwatch thread is forked successfully by kthread_run() during
initialization and therefore its state should be MTWATCH_DOMAIN_UP.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
drivers/xen/xenbus/xenbus_xs.c | 53 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 49 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 741dc54..7335e19 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -896,6 +896,32 @@ static struct xenbus_watch *find_watch(const char *token)
return NULL;
}

+static int xs_watch_insert_event(struct xs_watch_event *event, domid_t domid)
+{
+ struct mtwatch_domain *domain;
+ int ret = -1;
+
+ rcu_read_lock();
+
+ domain = mtwatch_find_domain(domid);
+ if (!domain) {
+ rcu_read_unlock();
+ return ret;
+ }
+
+ spin_lock(&domain->events_lock);
+ if (domain->state == MTWATCH_DOMAIN_UP) {
+ list_add_tail(&event->list, &domain->events);
+ wake_up(&domain->events_wq);
+ ret = 0;
+ }
+ spin_unlock(&domain->events_lock);
+
+ rcu_read_unlock();
+
+ return ret;
+}
+
int xs_watch_msg(struct xs_watch_event *event)
{
if (count_strings(event->body, event->len) != 2) {
@@ -908,10 +934,29 @@ int xs_watch_msg(struct xs_watch_event *event)
spin_lock(&watches_lock);
event->handle = find_watch(event->token);
if (event->handle != NULL) {
- spin_lock(&watch_events_lock);
- list_add_tail(&event->list, &watch_events);
- wake_up(&watch_events_waitq);
- spin_unlock(&watch_events_lock);
+ domid_t domid = 0;
+
+ if (xen_mtwatch && event->handle->get_domid)
+ domid = event->handle->get_domid(event->handle,
+ event->path,
+ event->token);
+
+ /*
+ * The event is processed by default xenwatch thread if:
+ *
+ * 1. The watch does not use xenwatch multithreading.
+ * 2. There is no per-domU xenwatch thread (or mtwatch
+ * domain) available for this domid.
+ * 3. The per-domU xenwatch thread is not created
+ * successfully by kthread_run() during initialization.
+ */
+ if (!(domid &&
+ xs_watch_insert_event(event, domid) == 0)) {
+ spin_lock(&watch_events_lock);
+ list_add_tail(&event->list, &watch_events);
+ wake_up(&watch_events_waitq);
+ spin_unlock(&watch_events_lock);
+ }
} else
kfree(event);
spin_unlock(&watches_lock);
--
2.7.4
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