1 files changed, 18 insertions, 4 deletions

diff --git a/src/evict/evict_lru.c b/src/evict/evict_lru.c
index 35b12e2b685..884c08a02df 100644
--- a/src/evict/evict_lru.c
+++ b/src/evict/evict_lru.c
@@ -791,7 +791,7 @@ __wt_evict_file_exclusive_on(WT_SESSION_IMPL *session, bool *evict_resetp)
 	btree = S2BT(session);
 	cache = S2C(session)->cache;
 
-	/* If the file wasn't evictable, there's no work to do. */
+	/* If the file was never evictable, there's no work to do. */
 	if (F_ISSET(btree, WT_BTREE_NO_EVICTION))
 		return (0);
 
@@ -800,9 +800,16 @@ __wt_evict_file_exclusive_on(WT_SESSION_IMPL *session, bool *evict_resetp)
 	 * the file will be queued for eviction after this point.
 	 */
 	__wt_spin_lock(session, &cache->evict_walk_lock);
-	F_SET(btree, WT_BTREE_NO_EVICTION);
+	if (!F_ISSET(btree, WT_BTREE_NO_EVICTION)) {
+		F_SET(btree, WT_BTREE_NO_EVICTION);
+		*evict_resetp = true;
+	}
 	__wt_spin_unlock(session, &cache->evict_walk_lock);
 
+	/* If some other operation has disabled eviction, we're done. */
+	if (!*evict_resetp)
+		return (0);
+
 	/* Clear any existing LRU eviction walk for the file. */
 	WT_ERR(__evict_request_walk_clear(session));
 
@@ -826,10 +833,10 @@ __wt_evict_file_exclusive_on(WT_SESSION_IMPL *session, bool *evict_resetp)
 	while (btree->evict_busy > 0)
 		__wt_yield();
 
-	*evict_resetp = true;
 	return (0);
 
 err:	F_CLR(btree, WT_BTREE_NO_EVICTION);
+	*evict_resetp = false;
 	return (ret);
 }
 
@@ -844,7 +851,14 @@ __wt_evict_file_exclusive_off(WT_SESSION_IMPL *session)
 
 	btree = S2BT(session);
 
-	WT_ASSERT(session, btree->evict_ref == NULL);
+	/*
+	 * We have seen subtle bugs with multiple threads racing to turn
+	 * eviction on/off.  Make races more likely in diagnostic builds.
+	 */
+	WT_DIAGNOSTIC_YIELD;
+
+	WT_ASSERT(session, btree->evict_ref == NULL &&
+	    F_ISSET(btree, WT_BTREE_NO_EVICTION));
 
 	F_CLR(btree, WT_BTREE_NO_EVICTION);
 }