WT-2498 Fix a bug in LSM where table drop could hang.

If there are open cursors.

2 files changed, 21 insertions, 16 deletions

diff --git a/src/lsm/lsm_tree.c b/src/lsm/lsm_tree.c
index e79d52c18e9..bd9d0671bde 100644
--- a/src/lsm/lsm_tree.c
+++ b/src/lsm/lsm_tree.c
@@ -85,7 +85,7 @@ __lsm_tree_discard(WT_SESSION_IMPL *session, WT_LSM_TREE *lsm_tree, bool final)
  *	Close an LSM tree structure.
  */
 static int
-__lsm_tree_close(WT_SESSION_IMPL *session, WT_LSM_TREE *lsm_tree)
+__lsm_tree_close(WT_SESSION_IMPL *session, WT_LSM_TREE *lsm_tree, bool wait)
 {
 	WT_DECL_RET;
 	int i;
@@ -94,10 +94,13 @@ __lsm_tree_close(WT_SESSION_IMPL *session, WT_LSM_TREE *lsm_tree)
 	F_CLR(lsm_tree, WT_LSM_TREE_ACTIVE);
 
 	/*
-	 * Wait for all LSM operations and work units that were in flight to
-	 * finish.
+	 * Wait for all LSM operations to drain. If WiredTiger is shutting
+	 * down also wait for the tree reference count to go to zero, otherwise
+	 * we know a user is holding a reference to the tree, so exclusive
+	 * access is not available.
 	 */
-	for (i = 0; lsm_tree->refcnt > 1 || lsm_tree->queue_ref > 0; ++i) {
+	for (i = 0;
+	    lsm_tree->refcnt > 1 && (wait || lsm_tree->queue_ref > 0); ++i) {
 		/*
 		 * Remove any work units from the manager queues. Do this step
 		 * repeatedly in case a work unit was in the process of being
@@ -145,7 +148,7 @@ __wt_lsm_tree_close_all(WT_SESSION_IMPL *session)
 		 * is unconditional.
 		 */
 		(void)__wt_atomic_add32(&lsm_tree->refcnt, 1);
-		WT_TRET(__lsm_tree_close(session, lsm_tree));
+		WT_TRET(__lsm_tree_close(session, lsm_tree, true));
 		WT_TRET(__lsm_tree_discard(session, lsm_tree, true));
 	}
 
@@ -380,9 +383,12 @@ __lsm_tree_find(WT_SESSION_IMPL *session,
 				 * open cursors - otherwise we can generate
 				 * spurious busy returns.
 				 */
-				if (__lsm_tree_close(session, lsm_tree) != 0 ||
-				    !__wt_atomic_cas32(
-				    &lsm_tree->refcnt, 0, 1)) {
+				(void)__wt_atomic_add32(&lsm_tree->refcnt, 1);
+				if (__lsm_tree_close(
+				    session, lsm_tree, false) != 0 ||
+				    lsm_tree->refcnt != 1) {
+					(void)__wt_atomic_sub32(
+					    &lsm_tree->refcnt, 1);
 					F_SET(lsm_tree, WT_LSM_TREE_ACTIVE);
 					lsm_tree->excl_session = NULL;
 					return (EBUSY);
diff --git a/test/suite/test_drop.py b/test/suite/test_drop.py
index 5663b85d661..52ea7251ab5 100644
--- a/test/suite/test_drop.py
+++ b/test/suite/test_drop.py
@@ -41,12 +41,11 @@ class test_drop(wttest.WiredTigerTestCase):
     scenarios = check_scenarios([
         ('file', dict(uri='file:')),
         ('table', dict(uri='table:')),
-        #Not yet: drop failing with an open cursor needs handle locking
-        #('table-lsm', dict(uri='table:', extra_config=',type=lsm')),
+        ('table-lsm', dict(uri='table:', extra_config=',type=lsm')),
     ])
 
     # Populate an object, remove it and confirm it no longer exists.
-    def drop(self, populate, with_cursor, close_session, drop_index):
+    def drop(self, populate, with_cursor, reopen, drop_index):
         uri = self.uri + self.name
         populate(self, uri, 'key_format=S' + self.extra_config, 10)
 
@@ -57,7 +56,7 @@ class test_drop(wttest.WiredTigerTestCase):
                 lambda: self.session.drop(uri, None))
             cursor.close()
 
-        if close_session:
+        if reopen:
             self.reopen_conn()
 
         if drop_index:
@@ -73,17 +72,17 @@ class test_drop(wttest.WiredTigerTestCase):
         # Try all combinations except dropping the index, the simple
         # case has no indices.
         for with_cursor in [False, True]:
-            for close_session in [False, True]:
-                self.drop(simple_populate, with_cursor, close_session, False)
+            for reopen in [False, True]:
+                self.drop(simple_populate, with_cursor, reopen, False)
 
         # A complex, multi-file table object.
         # Try all test combinations.
         if self.uri == "table:":
             for with_cursor in [False, True]:
-                for close_session in [False, True]:
+                for reopen in [False, True]:
                     for drop_index in [False, True]:
                         self.drop(complex_populate, with_cursor,
-                                  close_session, drop_index)
+                                  reopen, drop_index)
 
     # Test drop of a non-existent object: force succeeds, without force fails.
     def test_drop_dne(self):