sched/wait: Add add_wait_queue_priority()

[sfrench/cifs-2.6.git] / kernel / sched / wait.c

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 01f5d3020589de0e85ed2fa706c30bc0be547687..183cc6ae68a68d714a2fd4f7fcb845314f65871d 100644 (file)
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -37,6 +37,17 @@ void add_wait_queue_exclusive(struct wait_queue_head *wq_head, struct wait_queue
 }
 EXPORT_SYMBOL(add_wait_queue_exclusive);
 
+void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
+{
+       unsigned long flags;
+
+       wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY;
+       spin_lock_irqsave(&wq_head->lock, flags);
+       __add_wait_queue(wq_head, wq_entry);
+       spin_unlock_irqrestore(&wq_head->lock, flags);
+}
+EXPORT_SYMBOL_GPL(add_wait_queue_priority);
+
 void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
 {
        unsigned long flags;
@@ -57,7 +68,11 @@ EXPORT_SYMBOL(remove_wait_queue);
 /*
  * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
  * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
- * number) then we wake all the non-exclusive tasks and one exclusive task.
+ * number) then we wake that number of exclusive tasks, and potentially all
+ * the non-exclusive tasks. Normally, exclusive tasks will be at the end of
+ * the list and any non-exclusive tasks will be woken first. A priority task
+ * may be at the head of the list, and can consume the event without any other
+ * tasks being woken.
  *
  * There are circumstances in which we can try to wake a task which has already
  * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns