Reduce number of trx_sys.mutex references

trx->state change must be guarded by trx->mutex.
Moved mutex locking to MVCC::view_close().

storage/innobase/handler/ha_innodb.cc

@@ -16066,11 +16066,8 @@ ha_innobase::external_lock(
 				innobase_commit(ht, thd, TRUE);
 			}
 
-		} else if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
-			   && trx->read_view.is_open()) {
-			mutex_enter(&trx_sys.mutex);
+		} else if (trx->isolation_level <= TRX_ISO_READ_COMMITTED) {
 			trx_sys.mvcc.view_close(trx->read_view);
-			mutex_exit(&trx_sys.mutex);
 		}
 	}
 
@@ -16731,14 +16728,11 @@ ha_innobase::store_lock(
 		trx->isolation_level = innobase_map_isolation_level(
 			(enum_tx_isolation) thd_tx_isolation(thd));
 
-		if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
-		    && trx->read_view.is_open()) {
+		if (trx->isolation_level <= TRX_ISO_READ_COMMITTED) {
 
 			/* At low transaction isolation levels we let
 			each consistent read set its own snapshot */
-			mutex_enter(&trx_sys.mutex);
 			trx_sys.mvcc.view_close(trx->read_view);
-			mutex_enter(&trx_sys.mutex);
 		}
 	}
 

storage/innobase/include/read0read.h

@@ -55,13 +55,7 @@ class MVCC
     Close a view created by the above function.
     @param view view allocated by view_open.
   */
-  void view_close(ReadView &view)
-  {
-    view.close();
-    view.set_registered(false);
-    UT_LIST_REMOVE(m_views, &view);
-    ut_ad(validate());
-  }
+  void view_close(ReadView &view);
 
 
   /**

storage/innobase/read/read0read.cc

@@ -335,6 +335,21 @@ void MVCC::view_open(trx_t* trx)
   mutex_exit(&trx_sys.mutex);
 }
 
+
+void MVCC::view_close(ReadView &view)
+{
+  view.close();
+  if (view.is_registered())
+  {
+    mutex_enter(&trx_sys.mutex);
+    view.set_registered(false);
+    UT_LIST_REMOVE(m_views, &view);
+    ut_ad(validate());
+    mutex_exit(&trx_sys.mutex);
+  }
+}
+
+
 /**
 Copy state from another view.
 @param other		view to copy from */

storage/innobase/trx/trx0trx.cc

@@ -511,11 +511,7 @@ trx_free(trx_t*& trx)
 	trx->mod_tables.clear();
 
 	ut_ad(!trx->read_view.is_open());
-	if (trx->read_view.is_registered()) {
-		mutex_enter(&trx_sys.mutex);
 	trx_sys.mvcc.view_close(trx->read_view);
-		mutex_exit(&trx_sys.mutex);
-	}
 
 	/* trx locking state should have been reset before returning trx
 	to pool */
@@ -677,6 +673,8 @@ trx_disconnect_from_mysql(
 	trx_t*	trx,
 	bool	prepared)
 {
+	trx_sys.mvcc.view_close(trx->read_view);
+
 	mutex_enter(&trx_sys.mutex);
 
 	ut_ad(trx->in_mysql_trx_list);
@@ -684,10 +682,6 @@ trx_disconnect_from_mysql(
 
 	UT_LIST_REMOVE(trx_sys.mysql_trx_list, trx);
 
-	if (trx->read_view.is_open()) {
-		trx_sys.mvcc.view_close(trx->read_view);
-	}
-
 	if (prepared) {
 
 		ut_ad(trx_state_eq(trx, TRX_STATE_PREPARED));
@@ -2388,12 +2382,10 @@ trx_prepare(
 
 	DBUG_EXECUTE_IF("ib_trx_crash_during_xa_prepare_step", DBUG_SUICIDE(););
 
-	/*--------------------------------------*/
 	ut_a(trx->state == TRX_STATE_ACTIVE);
-	mutex_enter(&trx_sys.mutex);
+	trx_mutex_enter(trx);
 	trx->state = TRX_STATE_PREPARED;
-	mutex_exit(&trx_sys.mutex);
-	/*--------------------------------------*/
+	trx_mutex_exit(trx);
 
 	if (lsn) {
 		/* Depending on the my.cnf options, we may now write the log