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-rw-r--r--include/linux/wait.h12
-rw-r--r--kernel/sched/wait.c17
2 files changed, 27 insertions, 2 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 27fb99cfeb02..fe10e8570a52 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -22,6 +22,7 @@ int default_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int
#define WQ_FLAG_BOOKMARK 0x04
#define WQ_FLAG_CUSTOM 0x08
#define WQ_FLAG_DONE 0x10
+#define WQ_FLAG_PRIORITY 0x20
/*
* A single wait-queue entry structure:
@@ -164,11 +165,20 @@ static inline bool wq_has_sleeper(struct wait_queue_head *wq_head)
extern void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
extern void add_wait_queue_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
+extern void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
extern void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
static inline void __add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
{
- list_add(&wq_entry->entry, &wq_head->head);
+ struct list_head *head = &wq_head->head;
+ struct wait_queue_entry *wq;
+
+ list_for_each_entry(wq, &wq_head->head, entry) {
+ if (!(wq->flags & WQ_FLAG_PRIORITY))
+ break;
+ head = &wq->entry;
+ }
+ list_add(&wq_entry->entry, head);
}
/*
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 01f5d3020589..183cc6ae68a6 100644
--- 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

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