diff --git a/lib/libzpool/taskq.c b/lib/libzpool/taskq.c
index b1e71e998078..a2e457ef9e60 100644
--- a/lib/libzpool/taskq.c
+++ b/lib/libzpool/taskq.c
@@ -1,384 +1,386 @@
 /*
  * CDDL HEADER START
  *
  * The contents of this file are subject to the terms of the
  * Common Development and Distribution License (the "License").
  * You may not use this file except in compliance with the License.
  *
  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  * or https://opensource.org/licenses/CDDL-1.0.
  * See the License for the specific language governing permissions
  * and limitations under the License.
  *
  * When distributing Covered Code, include this CDDL HEADER in each
  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  * If applicable, add the following below this CDDL HEADER, with the
  * fields enclosed by brackets "[]" replaced with your own identifying
  * information: Portions Copyright [yyyy] [name of copyright owner]
  *
  * CDDL HEADER END
  */
 /*
  * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 /*
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
  * Copyright 2012 Garrett D'Amore <garrett@damore.org>.  All rights reserved.
  * Copyright (c) 2014 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
 
 int taskq_now;
 taskq_t *system_taskq;
 taskq_t *system_delay_taskq;
 
 static pthread_key_t taskq_tsd;
 
 #define	TASKQ_ACTIVE	0x00010000
 
 static taskq_ent_t *
 task_alloc(taskq_t *tq, int tqflags)
 {
 	taskq_ent_t *t;
 	int rv;
 
 again:	if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
 		ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC));
 		tq->tq_freelist = t->tqent_next;
 	} else {
 		if (tq->tq_nalloc >= tq->tq_maxalloc) {
 			if (!(tqflags & KM_SLEEP))
 				return (NULL);
 
 			/*
 			 * We don't want to exceed tq_maxalloc, but we can't
 			 * wait for other tasks to complete (and thus free up
 			 * task structures) without risking deadlock with
 			 * the caller.  So, we just delay for one second
 			 * to throttle the allocation rate. If we have tasks
 			 * complete before one second timeout expires then
 			 * taskq_ent_free will signal us and we will
 			 * immediately retry the allocation.
 			 */
 			tq->tq_maxalloc_wait++;
 			rv = cv_timedwait(&tq->tq_maxalloc_cv,
 			    &tq->tq_lock, ddi_get_lbolt() + hz);
 			tq->tq_maxalloc_wait--;
 			if (rv > 0)
 				goto again;		/* signaled */
 		}
 		mutex_exit(&tq->tq_lock);
 
 		t = kmem_alloc(sizeof (taskq_ent_t), tqflags);
 
 		mutex_enter(&tq->tq_lock);
 		if (t != NULL) {
 			/* Make sure we start without any flags */
 			t->tqent_flags = 0;
 			tq->tq_nalloc++;
 		}
 	}
 	return (t);
 }
 
 static void
 task_free(taskq_t *tq, taskq_ent_t *t)
 {
 	if (tq->tq_nalloc <= tq->tq_minalloc) {
 		t->tqent_next = tq->tq_freelist;
 		tq->tq_freelist = t;
 	} else {
 		tq->tq_nalloc--;
 		mutex_exit(&tq->tq_lock);
 		kmem_free(t, sizeof (taskq_ent_t));
 		mutex_enter(&tq->tq_lock);
 	}
 
 	if (tq->tq_maxalloc_wait)
 		cv_signal(&tq->tq_maxalloc_cv);
 }
 
 taskqid_t
 taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
 {
 	taskq_ent_t *t;
 
 	if (taskq_now) {
 		func(arg);
 		return (1);
 	}
 
 	mutex_enter(&tq->tq_lock);
 	ASSERT(tq->tq_flags & TASKQ_ACTIVE);
 	if ((t = task_alloc(tq, tqflags)) == NULL) {
 		mutex_exit(&tq->tq_lock);
 		return (0);
 	}
 	if (tqflags & TQ_FRONT) {
 		t->tqent_next = tq->tq_task.tqent_next;
 		t->tqent_prev = &tq->tq_task;
 	} else {
 		t->tqent_next = &tq->tq_task;
 		t->tqent_prev = tq->tq_task.tqent_prev;
 	}
 	t->tqent_next->tqent_prev = t;
 	t->tqent_prev->tqent_next = t;
 	t->tqent_func = func;
 	t->tqent_arg = arg;
 	t->tqent_flags = 0;
 	cv_signal(&tq->tq_dispatch_cv);
 	mutex_exit(&tq->tq_lock);
 	return (1);
 }
 
 taskqid_t
 taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags,
     clock_t expire_time)
 {
 	(void) tq, (void) func, (void) arg, (void) tqflags, (void) expire_time;
 	return (0);
 }
 
 int
 taskq_empty_ent(taskq_ent_t *t)
 {
 	return (t->tqent_next == NULL);
 }
 
 void
 taskq_init_ent(taskq_ent_t *t)
 {
 	t->tqent_next = NULL;
 	t->tqent_prev = NULL;
 	t->tqent_func = NULL;
 	t->tqent_arg = NULL;
 	t->tqent_flags = 0;
 }
 
 void
 taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
     taskq_ent_t *t)
 {
 	ASSERT(func != NULL);
 
 	/*
 	 * Mark it as a prealloc'd task.  This is important
 	 * to ensure that we don't free it later.
 	 */
 	t->tqent_flags |= TQENT_FLAG_PREALLOC;
 	/*
 	 * Enqueue the task to the underlying queue.
 	 */
 	mutex_enter(&tq->tq_lock);
 
 	if (flags & TQ_FRONT) {
 		t->tqent_next = tq->tq_task.tqent_next;
 		t->tqent_prev = &tq->tq_task;
 	} else {
 		t->tqent_next = &tq->tq_task;
 		t->tqent_prev = tq->tq_task.tqent_prev;
 	}
 	t->tqent_next->tqent_prev = t;
 	t->tqent_prev->tqent_next = t;
 	t->tqent_func = func;
 	t->tqent_arg = arg;
 	cv_signal(&tq->tq_dispatch_cv);
 	mutex_exit(&tq->tq_lock);
 }
 
 void
 taskq_wait(taskq_t *tq)
 {
 	mutex_enter(&tq->tq_lock);
 	while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0)
 		cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 	mutex_exit(&tq->tq_lock);
 }
 
 void
 taskq_wait_id(taskq_t *tq, taskqid_t id)
 {
 	(void) id;
 	taskq_wait(tq);
 }
 
 void
 taskq_wait_outstanding(taskq_t *tq, taskqid_t id)
 {
 	(void) id;
 	taskq_wait(tq);
 }
 
 static __attribute__((noreturn)) void
 taskq_thread(void *arg)
 {
 	taskq_t *tq = arg;
 	taskq_ent_t *t;
 	boolean_t prealloc;
 
 	VERIFY0(pthread_setspecific(taskq_tsd, tq));
 
 	mutex_enter(&tq->tq_lock);
 	while (tq->tq_flags & TASKQ_ACTIVE) {
 		if ((t = tq->tq_task.tqent_next) == &tq->tq_task) {
 			if (--tq->tq_active == 0)
 				cv_broadcast(&tq->tq_wait_cv);
 			cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
 			tq->tq_active++;
 			continue;
 		}
 		t->tqent_prev->tqent_next = t->tqent_next;
 		t->tqent_next->tqent_prev = t->tqent_prev;
 		t->tqent_next = NULL;
 		t->tqent_prev = NULL;
 		prealloc = t->tqent_flags & TQENT_FLAG_PREALLOC;
 		mutex_exit(&tq->tq_lock);
 
 		rw_enter(&tq->tq_threadlock, RW_READER);
 		t->tqent_func(t->tqent_arg);
 		rw_exit(&tq->tq_threadlock);
 
 		mutex_enter(&tq->tq_lock);
 		if (!prealloc)
 			task_free(tq, t);
 	}
 	tq->tq_nthreads--;
 	cv_broadcast(&tq->tq_wait_cv);
 	mutex_exit(&tq->tq_lock);
 	thread_exit();
 }
 
 taskq_t *
 taskq_create(const char *name, int nthreads, pri_t pri,
     int minalloc, int maxalloc, uint_t flags)
 {
 	(void) pri;
 	taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
 	int t;
 
 	if (flags & TASKQ_THREADS_CPU_PCT) {
 		int pct;
 		ASSERT3S(nthreads, >=, 0);
 		ASSERT3S(nthreads, <=, 100);
 		pct = MIN(nthreads, 100);
 		pct = MAX(pct, 0);
 
 		nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
 		nthreads = MAX(nthreads, 1);	/* need at least 1 thread */
 	} else {
 		ASSERT3S(nthreads, >=, 1);
 	}
 
 	rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
 	mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
 	cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&tq->tq_maxalloc_cv, NULL, CV_DEFAULT, NULL);
 	(void) strlcpy(tq->tq_name, name, sizeof (tq->tq_name));
 	tq->tq_flags = flags | TASKQ_ACTIVE;
 	tq->tq_active = nthreads;
 	tq->tq_nthreads = nthreads;
 	tq->tq_minalloc = minalloc;
 	tq->tq_maxalloc = maxalloc;
 	tq->tq_task.tqent_next = &tq->tq_task;
 	tq->tq_task.tqent_prev = &tq->tq_task;
 	tq->tq_threadlist = kmem_alloc(nthreads * sizeof (kthread_t *),
 	    KM_SLEEP);
 
 	if (flags & TASKQ_PREPOPULATE) {
 		mutex_enter(&tq->tq_lock);
 		while (minalloc-- > 0)
 			task_free(tq, task_alloc(tq, KM_SLEEP));
 		mutex_exit(&tq->tq_lock);
 	}
 
 	for (t = 0; t < nthreads; t++)
 		VERIFY((tq->tq_threadlist[t] = thread_create(NULL, 0,
 		    taskq_thread, tq, 0, &p0, TS_RUN, pri)) != NULL);
 
 	return (tq);
 }
 
 void
 taskq_destroy(taskq_t *tq)
 {
 	int nthreads = tq->tq_nthreads;
 
 	taskq_wait(tq);
 
 	mutex_enter(&tq->tq_lock);
 
 	tq->tq_flags &= ~TASKQ_ACTIVE;
 	cv_broadcast(&tq->tq_dispatch_cv);
 
 	while (tq->tq_nthreads != 0)
 		cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 
 	tq->tq_minalloc = 0;
 	while (tq->tq_nalloc != 0) {
 		ASSERT(tq->tq_freelist != NULL);
-		task_free(tq, task_alloc(tq, KM_SLEEP));
+		taskq_ent_t *tqent_nexttq = tq->tq_freelist->tqent_next;
+		task_free(tq, tq->tq_freelist);
+		tq->tq_freelist = tqent_nexttq;
 	}
 
 	mutex_exit(&tq->tq_lock);
 
 	kmem_free(tq->tq_threadlist, nthreads * sizeof (kthread_t *));
 
 	rw_destroy(&tq->tq_threadlock);
 	mutex_destroy(&tq->tq_lock);
 	cv_destroy(&tq->tq_dispatch_cv);
 	cv_destroy(&tq->tq_wait_cv);
 	cv_destroy(&tq->tq_maxalloc_cv);
 
 	kmem_free(tq, sizeof (taskq_t));
 }
 
 int
 taskq_member(taskq_t *tq, kthread_t *t)
 {
 	int i;
 
 	if (taskq_now)
 		return (1);
 
 	for (i = 0; i < tq->tq_nthreads; i++)
 		if (tq->tq_threadlist[i] == t)
 			return (1);
 
 	return (0);
 }
 
 taskq_t *
 taskq_of_curthread(void)
 {
 	return (pthread_getspecific(taskq_tsd));
 }
 
 int
 taskq_cancel_id(taskq_t *tq, taskqid_t id)
 {
 	(void) tq, (void) id;
 	return (ENOENT);
 }
 
 void
 system_taskq_init(void)
 {
 	VERIFY0(pthread_key_create(&taskq_tsd, NULL));
 	system_taskq = taskq_create("system_taskq", 64, maxclsyspri, 4, 512,
 	    TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 	system_delay_taskq = taskq_create("delay_taskq", 4, maxclsyspri, 4,
 	    512, TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 }
 
 void
 system_taskq_fini(void)
 {
 	taskq_destroy(system_taskq);
 	system_taskq = NULL; /* defensive */
 	taskq_destroy(system_delay_taskq);
 	system_delay_taskq = NULL;
 	VERIFY0(pthread_key_delete(taskq_tsd));
 }