Bug #16411457 MASTER THREAD CANNOT EXIT FLUSH_LOOP WHEN

INNODB_FAST_SHUTDOWN IS 2

Problem:

When innodb_fast_shutdown is set to 2 and the master thread enters
flush loop, under some circumstances it will not be able to exit it.
This may lead to a shutdown hanging.

This is happening because of the following:

1. In the flush_loop block of code, if the srv_fast_shutdown is
   equal to 2 (very fast shutdown), then we do not flush dirty
   pages in buffer pool to disk.
 
2. In the same flush_loop block of code, if the number of dirty
   pages is more than user specified limit, we go to step 1.

This results in infinite loop.

Solution:

When we are in the process of doing a very fast shutdown, don't
do step 2 above.

rb#2328 approved by Inaam.

storage/innobase/srv/srv0srv.c

@@ -3100,14 +3100,18 @@ background_loop:
 flush_loop:
 	srv_main_thread_op_info = "flushing buffer pool pages";
 	srv_main_flush_loops++;
-	if (srv_fast_shutdown < 2) {
+	if (srv_fast_shutdown < 2 || srv_shutdown_state == SRV_SHUTDOWN_NONE) {
 		n_pages_flushed = buf_flush_list(
 			  PCT_IO(100), IB_ULONGLONG_MAX);
 	} else {
 		/* In the fastest shutdown we do not flush the buffer pool
 		to data files: we set n_pages_flushed to 0 artificially. */
+		ut_ad(srv_fast_shutdown == 2);
+		ut_ad(srv_shutdown_state > 0);
 
 		n_pages_flushed = 0;
+
+		DBUG_PRINT("master", ("doing very fast shutdown"));
 	}
 
 	srv_main_thread_op_info = "reserving kernel mutex";
@@ -3129,7 +3133,12 @@ flush_loop:
 
 	log_checkpoint(TRUE, FALSE);
 
-	if (buf_get_modified_ratio_pct() > srv_max_buf_pool_modified_pct) {
+	if (!(srv_fast_shutdown == 2 && srv_shutdown_state > 0)
+	    && (buf_get_modified_ratio_pct()
+		> srv_max_buf_pool_modified_pct)) {
+
+		/* If the server is doing a very fast shutdown, then
+		we will not come here. */
 
 		/* Try to keep the number of modified pages in the
 		buffer pool under the limit wished by the user */