9017 Introduce taskq_empty()
Reviewed by: Bryan Cantrill <bryan@joyent.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Yuri Pankov <yuripv@yuripv.net>

@@ -24,10 +24,11 @@
  */
 /*
  * Copyright 2012 Garrett D'Amore <garrett@damore.org>.  All rights reserved.
  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
  * Copyright 2017 RackTop Systems.
+ * Copyright 2018, Joyent, Inc.
  */
 
 #include <sys/taskq_impl.h>
 
 #include <sys/class.h>

@@ -210,10 +211,22 @@
         t->tqent_arg = arg;
         cv_signal(&tq->tq_dispatch_cv);
         mutex_exit(&tq->tq_lock);
 }
 
+boolean_t
+taskq_empty(taskq_t *tq)
+{
+        boolean_t rv;
+
+        mutex_enter(&tq->tq_lock);
+        rv = (tq->tq_task.tqent_next == &tq->tq_task) && (tq->tq_active == 0);
+        mutex_exit(&tq->tq_lock);
+
+        return (rv);
+}
+
 void
 taskq_wait(taskq_t *tq)
 {
         mutex_enter(&tq->tq_lock);
         while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0)