[Xen-devel] [PATCH v2 04/17] Save/Restore Support: Add xenbus_release_wait_for_watch

[Bruno Alvisio <bruno.alvisio@xxxxxxxxx>]

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@xxxxxxxxx>
Reviewed-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
---
Changed since v1:
  * Added doc for change in release_xenbus_id
---
 include/xenbus.h |  1 +
 xenbus/xenbus.c  | 10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/xenbus.h b/include/xenbus.h
index 12391b9..b2d5072 100644
--- 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 636786c..c2d2bd1 100644
--- 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);
 }
-- 
2.3.2 (Apple Git-55)


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