Index: spa_misc.c
===================================================================
--- spa_misc.c	(revision 258354)
+++ spa_misc.c	(working copy)
@@ -312,7 +312,7 @@ spa_config_lock_init(spa_t *spa)
 {
 	for (int i = 0; i < SCL_LOCKS; i++) {
 		spa_config_lock_t *scl = &spa->spa_config_lock[i];
-		mutex_init(&scl->scl_lock, NULL, MUTEX_DEFAULT, NULL);
+		rw_init(&scl->scl_lock, NULL, RW_DEFAULT, NULL);
 		cv_init(&scl->scl_cv, NULL, CV_DEFAULT, NULL);
 		refcount_create_untracked(&scl->scl_count);
 		scl->scl_writer = NULL;
@@ -325,7 +325,7 @@ spa_config_lock_destroy(spa_t *spa)
 {
 	for (int i = 0; i < SCL_LOCKS; i++) {
 		spa_config_lock_t *scl = &spa->spa_config_lock[i];
-		mutex_destroy(&scl->scl_lock);
+		rw_destroy(&scl->scl_lock);
 		cv_destroy(&scl->scl_cv);
 		refcount_destroy(&scl->scl_count);
 		ASSERT(scl->scl_writer == NULL);
@@ -340,10 +340,10 @@ spa_config_tryenter(spa_t *spa, int locks, void *t
 		spa_config_lock_t *scl = &spa->spa_config_lock[i];
 		if (!(locks & (1 << i)))
 			continue;
-		mutex_enter(&scl->scl_lock);
+		rw_enter(&scl->scl_lock, rw);
 		if (rw == RW_READER) {
 			if (scl->scl_writer || scl->scl_write_wanted) {
-				mutex_exit(&scl->scl_lock);
+				rw_exit(&scl->scl_lock);
 				spa_config_exit(spa, locks ^ (1 << i), tag);
 				return (0);
 			}
@@ -350,7 +350,7 @@ spa_config_tryenter(spa_t *spa, int locks, void *t
 		} else {
 			ASSERT(scl->scl_writer != curthread);
 			if (!refcount_is_zero(&scl->scl_count)) {
-				mutex_exit(&scl->scl_lock);
+				rw_exit(&scl->scl_lock);
 				spa_config_exit(spa, locks ^ (1 << i), tag);
 				return (0);
 			}
@@ -357,7 +357,7 @@ spa_config_tryenter(spa_t *spa, int locks, void *t
 			scl->scl_writer = curthread;
 		}
 		(void) refcount_add(&scl->scl_count, tag);
-		mutex_exit(&scl->scl_lock);
+		rw_exit(&scl->scl_lock);
 	}
 	return (1);
 }
@@ -375,7 +375,7 @@ spa_config_enter(spa_t *spa, int locks, void *tag,
 			wlocks_held |= (1 << i);
 		if (!(locks & (1 << i)))
 			continue;
-		mutex_enter(&scl->scl_lock);
+		rw_enter(&scl->scl_lock, rw);
 		if (rw == RW_READER) {
 			while (scl->scl_writer || scl->scl_write_wanted) {
 				cv_wait(&scl->scl_cv, &scl->scl_lock);
@@ -390,7 +390,7 @@ spa_config_enter(spa_t *spa, int locks, void *tag,
 			scl->scl_writer = curthread;
 		}
 		(void) refcount_add(&scl->scl_count, tag);
-		mutex_exit(&scl->scl_lock);
+		rw_exit(&scl->scl_lock);
 	}
 	ASSERT(wlocks_held <= locks);
 }
@@ -402,7 +402,8 @@ spa_config_exit(spa_t *spa, int locks, void *tag)
 		spa_config_lock_t *scl = &spa->spa_config_lock[i];
 		if (!(locks & (1 << i)))
 			continue;
-		mutex_enter(&scl->scl_lock);
+		rw_enter(&scl->scl_lock,
+		    scl->scl_writer == curthread ? RW_WRITER : RW_READER);
 		ASSERT(!refcount_is_zero(&scl->scl_count));
 		if (refcount_remove(&scl->scl_count, tag) == 0) {
 			ASSERT(scl->scl_writer == NULL ||
@@ -410,7 +411,7 @@ spa_config_exit(spa_t *spa, int locks, void *tag)
 			scl->scl_writer = NULL;	/* OK in either case */
 			cv_broadcast(&scl->scl_cv);
 		}
-		mutex_exit(&scl->scl_lock);
+		rw_exit(&scl->scl_lock);
 	}
 }
 
Index: sys/spa_impl.h
===================================================================
--- sys/spa_impl.h	(revision 258354)
+++ sys/spa_impl.h	(working copy)
@@ -69,7 +69,7 @@ struct spa_aux_vdev {
 };
 
 typedef struct spa_config_lock {
-	kmutex_t	scl_lock;
+	krwlock_t	scl_lock;
 	kthread_t	*scl_writer;
 	int		scl_write_wanted;
 	kcondvar_t	scl_cv;