Implement taskqueue_block() and taskqueue_unblock(). These functions allow

the owner of a queue to block and unblock execution of the tasks in the
queue while allowing tasks to continue to be added queue.  Combining this
with taskqueue_drain() allows a queue to be safely disabled.  The unblock
function may run (or schedule to run) the queue when it is called, just as
calling taskqueue_enqueue() would.

Reviewed by: jhb, sam

2 files changed, 30 insertions, 1 deletions

diff --git a/sys/kern/subr_taskqueue.c b/sys/kern/subr_taskqueue.c
index c3ddb5f38765..76648611c2d2 100644
--- a/sys/kern/subr_taskqueue.c
+++ b/sys/kern/subr_taskqueue.c
@@ -63,6 +63,8 @@ struct taskqueue {
 };
 
 #define	TQ_FLAGS_ACTIVE		(1 << 0)
+#define	TQ_FLAGS_BLOCKED	(1 << 1)
+#define	TQ_FLAGS_PENDING	(1 << 2)
 
 static __inline void
 TQ_LOCK(struct taskqueue *tq)
@@ -224,7 +226,10 @@ taskqueue_enqueue(struct taskqueue *queue, struct task *task)
 	}
 
 	task->ta_pending = 1;
-	queue->tq_enqueue(queue->tq_context);
+	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
+		queue->tq_enqueue(queue->tq_context);
+	else
+		queue->tq_flags |= TQ_FLAGS_PENDING;
 
 	TQ_UNLOCK(queue);
 
@@ -232,6 +237,28 @@ taskqueue_enqueue(struct taskqueue *queue, struct task *task)
 }
 
 void
+taskqueue_block(struct taskqueue *queue)
+{
+
+	TQ_LOCK(queue);
+	queue->tq_flags |= TQ_FLAGS_BLOCKED;
+	TQ_UNLOCK(queue);
+}
+
+void
+taskqueue_unblock(struct taskqueue *queue)
+{
+
+	TQ_LOCK(queue);
+	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
+	if (queue->tq_flags & TQ_FLAGS_PENDING) {
+		queue->tq_flags &= ~TQ_FLAGS_PENDING;
+		queue->tq_enqueue(queue->tq_context);
+	}
+	TQ_UNLOCK(queue);
+}
+
+void
 taskqueue_run(struct taskqueue *queue)
 {
 	struct task *task;
diff --git a/sys/sys/taskqueue.h b/sys/sys/taskqueue.h
index c980fc187565..4065a58b3ed1 100644
--- a/sys/sys/taskqueue.h
+++ b/sys/sys/taskqueue.h
@@ -58,6 +58,8 @@ void	taskqueue_drain(struct taskqueue *queue, struct task *task);
 struct taskqueue *taskqueue_find(const char *name);
 void	taskqueue_free(struct taskqueue *queue);
 void	taskqueue_run(struct taskqueue *queue);
+void	taskqueue_block(struct taskqueue *queue);
+void	taskqueue_unblock(struct taskqueue *queue);
 
 /*
  * Functions for dedicated thread taskqueues