Added counter of number of missed wakeups of InnoDB threads

storage/innobase/handler/ha_innodb.cc

@@ -433,6 +433,8 @@ static SHOW_VAR innodb_status_variables[]= {
   (char*) &export_vars.innodb_rows_read,		  SHOW_LONG},
   {"rows_updated",
   (char*) &export_vars.innodb_rows_updated,		  SHOW_LONG},
+  {"wake_ups",
+  (char*) &export_vars.innodb_wake_ups,		  SHOW_LONG},
   {NullS, NullS, SHOW_LONG}
 };
 

storage/innobase/include/srv0srv.h

@@ -251,6 +251,9 @@ extern ulint srv_read_ahead_seq;
 /* variable to count the number of random read-aheads were done */
 extern ulint srv_read_ahead_rnd;
 
+/* Number of threads that may have missed a lock wait wakeup */
+extern ulint sync_wake_ups;
+
 /* In this structure we store status variables to be passed to MySQL */
 typedef struct export_var_struct export_struc;
 
@@ -545,6 +548,7 @@ struct export_var_struct{
 	ulint innodb_rows_inserted;
 	ulint innodb_rows_updated;
 	ulint innodb_rows_deleted;
+	ulint innodb_wake_ups;
 };
 
 /* The server system struct */

storage/innobase/srv/srv0srv.c

@@ -1939,6 +1939,7 @@ srv_export_innodb_status(void)
 	export_vars.innodb_rows_inserted = srv_n_rows_inserted;
 	export_vars.innodb_rows_updated = srv_n_rows_updated;
 	export_vars.innodb_rows_deleted = srv_n_rows_deleted;
+	export_vars.innodb_wake_ups = sync_wake_ups;
 
 	mutex_exit(&srv_innodb_monitor_mutex);
 }

storage/innobase/sync/sync0arr.c

@@ -110,6 +110,10 @@ struct sync_array_struct {
 					since creation of the array */
 };
 
+/* Counts the number of times that sync_arr_wake_threads_if_sema_free has
+ * found a thread that can run because it may have missed a wakeup signal. */
+ulint sync_wake_ups = 0;
+
 #ifdef UNIV_SYNC_DEBUG
 /**********************************************************************
 This function is called only in the debug version. Detects a deadlock
@@ -481,7 +485,11 @@ sync_array_cell_print(
 		   || type == RW_LOCK_WAIT_EX
 		   || type == RW_LOCK_SHARED) {
 
-		fputs(type == RW_LOCK_EX ? "X-lock on" : "S-lock on", file);
+		switch(type) {
+		case RW_LOCK_EX:      fputs("X-lock on", file);      break;
+		case RW_LOCK_WAIT_EX: fputs("wait-X-lock on", file); break;
+		default:              fputs("S-lock on", file);      break;
+		}
 
 		rwlock = cell->old_wait_rw_lock;
 
@@ -884,6 +892,7 @@ sync_arr_wake_threads_if_sema_free(void)
 			event = sync_cell_get_event(cell);
 
 			os_event_set(event);
+			sync_wake_ups++;
 		}
 
 	}