Save/Restore Support: Add xenbus_release_wait_for_watch

xenbus_release_wait_for_watch generates a fake event to trigger make
xenbus_wait_for_watch return. This is necessary to wake up waiting threads.

release_xenbus_id additionally checks if the number of requests == 0 to wake
up the 'waiting' suspend xenbus thread.

Signed-off-by: Bruno Alvisio <bruno.alvisio@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/include/xenbus.h b/include/xenbus.h
index 12391b9b06fffc524c91a0156ee75b8540d661cb..b2d5072b53bc238086b898407a4c11a452f995db 100644 (file)
--- a/include/xenbus.h
+++ b/include/xenbus.h
@@ -42,6 +42,7 @@ char *xenbus_unwatch_path_token(xenbus_transaction_t xbt, const char *path, cons
 extern struct wait_queue_head xenbus_watch_queue;
 void xenbus_wait_for_watch(xenbus_event_queue *queue);
 char **xenbus_wait_for_watch_return(xenbus_event_queue *queue);
+void xenbus_release_wait_for_watch(xenbus_event_queue *queue);
 char* xenbus_wait_for_value(const char *path, const char *value, xenbus_event_queue *queue);
 char *xenbus_wait_for_state_change(const char* path, XenbusState *state, xenbus_event_queue *queue);
 char *xenbus_switch_state(xenbus_transaction_t xbt, const char* path, XenbusState state);

diff --git a/xenbus/xenbus.c b/xenbus/xenbus.c
index 636786ceb54e81d1f4de34a18a0d03b7a0f82706..c2d2bd1758575d5dbd20679d8e7484438877c7d1 100644 (file)
--- a/xenbus/xenbus.c
+++ b/xenbus/xenbus.c
@@ -129,6 +129,14 @@ void xenbus_wait_for_watch(xenbus_event_queue *queue)
         printk("unexpected path returned by watch\n");
 }
 
+void xenbus_release_wait_for_watch(xenbus_event_queue *queue)
+{
+    struct xenbus_event *event = malloc(sizeof(*event));
+    event->next = *queue;
+    *queue = event;
+    wake_up(&xenbus_watch_queue);
+}
+
 char* xenbus_wait_for_value(const char* path, const char* value, xenbus_event_queue *queue)
 {
     if (!queue)
@@ -318,7 +326,7 @@ static void release_xenbus_id(int id)
     req_info[id].in_use = 0;
     nr_live_reqs--;
     req_info[id].in_use = 0;
-    if (nr_live_reqs == NR_REQS - 1)
+    if (nr_live_reqs == 0 || nr_live_reqs == NR_REQS - 1)
         wake_up(&req_wq);
     spin_unlock(&req_lock);
 }