Bug#16292043 RACE CONDITION IN SRV_EXPORT_INNODB_STATUS() WHEN ACCESSING PURGE_SYS->VIEW

srv_export_innodb_status(): Read the purge_sys fields while holding
purge_sys->latch.

Approved by Sunny Bains

storage/innobase/srv/srv0srv.c

@@ -1922,21 +1922,32 @@ srv_export_innodb_status(void)
 	export_vars.innodb_rows_deleted = srv_n_rows_deleted;
 
 #ifdef UNIV_DEBUG
-	if (ut_dulint_cmp(trx_sys->max_trx_id, purge_sys->done_trx_no) < 0) {
-		export_vars.innodb_purge_trx_id_age = 0;
-	} else {
-		export_vars.innodb_purge_trx_id_age =
-		  ut_dulint_minus(trx_sys->max_trx_id, purge_sys->done_trx_no);
-	}
+	{
+		dulint	done_trx_no;
+		dulint	up_limit_id;
+
+		rw_lock_s_lock(&purge_sys->latch);
+		done_trx_no	= purge_sys->done_trx_no;
+		up_limit_id	= purge_sys->view
+			? purge_sys->view->up_limit_id
+			: ut_dulint_zero;
+		rw_lock_s_unlock(&purge_sys->latch);
+
+		if (ut_dulint_cmp(trx_sys->max_trx_id, done_trx_no) < 0) {
+			export_vars.innodb_purge_trx_id_age = 0;
+		} else {
+			export_vars.innodb_purge_trx_id_age = ut_dulint_minus(
+				trx_sys->max_trx_id, done_trx_no);
+		}
 
-	if (!purge_sys->view
-	    || ut_dulint_cmp(trx_sys->max_trx_id,
-			     purge_sys->view->up_limit_id) < 0) {
-		export_vars.innodb_purge_view_trx_id_age = 0;
-	} else {
-		export_vars.innodb_purge_view_trx_id_age =
-		  ut_dulint_minus(trx_sys->max_trx_id,
-				  purge_sys->view->up_limit_id);
+		if (ut_dulint_is_zero(up_limit_id)
+		    || ut_dulint_cmp(trx_sys->max_trx_id, up_limit_id) < 0) {
+			export_vars.innodb_purge_view_trx_id_age = 0;
+		} else {
+			export_vars.innodb_purge_view_trx_id_age =
+				ut_dulint_minus(trx_sys->max_trx_id,
+						up_limit_id);
+		}
 	}
 #endif /* UNIV_DEBUG */
 

storage/innodb_plugin/srv/srv0srv.c

 /*****************************************************************************
 
-Copyright (c) 1995, 2010, Innobase Oy. All Rights Reserved.
+Copyright (c) 1995, 2013, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, 2009 Google Inc.
 Copyright (c) 2009, Percona Inc.
 
@@ -257,7 +257,7 @@ UNIV_INTERN ulint srv_data_read = 0;
 /* Internal setting for "innodb_stats_method". Decides how InnoDB treats
 NULL value when collecting statistics. By default, it is set to
 SRV_STATS_NULLS_EQUAL(0), ie. all NULL value are treated equal */
-ulong srv_innodb_stats_method = SRV_STATS_NULLS_EQUAL;
+UNIV_INTERN ulong srv_innodb_stats_method = SRV_STATS_NULLS_EQUAL;
 
 /* here we count the amount of data written in total (in bytes) */
 UNIV_INTERN ulint srv_data_written = 0;
@@ -1978,21 +1978,32 @@ srv_export_innodb_status(void)
 	export_vars.innodb_rows_deleted = srv_n_rows_deleted;
 
 #ifdef UNIV_DEBUG
-	if (ut_dulint_cmp(trx_sys->max_trx_id, purge_sys->done_trx_no) < 0) {
-		export_vars.innodb_purge_trx_id_age = 0;
-	} else {
-		export_vars.innodb_purge_trx_id_age =
-		  ut_dulint_minus(trx_sys->max_trx_id, purge_sys->done_trx_no);
-	}
+	{
+		dulint	done_trx_no;
+		dulint	up_limit_id;
+
+		rw_lock_s_lock(&purge_sys->latch);
+		done_trx_no	= purge_sys->done_trx_no;
+		up_limit_id	= purge_sys->view
+			? purge_sys->view->up_limit_id
+			: ut_dulint_zero;
+		rw_lock_s_unlock(&purge_sys->latch);
+
+		if (ut_dulint_cmp(trx_sys->max_trx_id, done_trx_no) < 0) {
+			export_vars.innodb_purge_trx_id_age = 0;
+		} else {
+			export_vars.innodb_purge_trx_id_age = ut_dulint_minus(
+				trx_sys->max_trx_id, done_trx_no);
+		}
 
-	if (!purge_sys->view
-	    || ut_dulint_cmp(trx_sys->max_trx_id,
-			     purge_sys->view->up_limit_id) < 0) {
-		export_vars.innodb_purge_view_trx_id_age = 0;
-	} else {
-		export_vars.innodb_purge_view_trx_id_age =
-		  ut_dulint_minus(trx_sys->max_trx_id,
-				  purge_sys->view->up_limit_id);
+		if (ut_dulint_is_zero(up_limit_id)
+		    || ut_dulint_cmp(trx_sys->max_trx_id, up_limit_id) < 0) {
+			export_vars.innodb_purge_view_trx_id_age = 0;
+		} else {
+			export_vars.innodb_purge_view_trx_id_age =
+				ut_dulint_minus(trx_sys->max_trx_id,
+						up_limit_id);
+		}
 	}
 #endif /* UNIV_DEBUG */