MDEV-12146 Deprecate and remove innodb_instrument_semaphores

MDEV-7618 introduced configuration parameter innodb_instrument_semaphores
in MariaDB Server 10.1. The parameter seems to only affect the rw-lock
X-latch acquisition. Extra fields are added to rw_lock_t to remember one
X-latch holder or waiter. These fields are not being consulted or reported
anywhere. This is basically only adding code bloat.

If the intention is to debug hangs or deadlocks, we have better tools for
that in the debug server, and for the non-debug server, core dumps can
reveal a lot. For example, the mini-transaction memo records the
currently held buffer block or index rw-locks, to be released at
mtr_t::commit().

The configuration parameter innodb_instrument_semaphores will be
deprecated in 10.2.5 and removed in 10.3.0.

rw_lock_t: Remove the members lock_name, file_name, line, thread_id
which did not affect any output.

1 files changed, 0 insertions, 17 deletions

diff --git a/storage/innobase/sync/sync0rw.cc b/storage/innobase/sync/sync0rw.cc
index 5cb90ce5b8d..9160d9c8bee 100644
--- a/storage/innobase/sync/sync0rw.cc
+++ b/storage/innobase/sync/sync0rw.cc
@@ -202,7 +202,6 @@ rw_lock_create_func(
 #ifdef UNIV_DEBUG
 	latch_level_t	level,		/*!< in: level */
 #endif /* UNIV_DEBUG */
-	const char*	cmutex_name,	/*!< in: mutex name */
 	const char*	cfile_name,	/*!< in: file name where created */
 	ulint		cline)		/*!< in: file line where created */
 {
@@ -238,10 +237,7 @@ rw_lock_create_func(
 	less than 8192. cline is unsigned:13. */
 	ut_ad(cline <= 8192);
 	lock->cline = (unsigned int) cline;
-	lock->lock_name = cmutex_name;
 	lock->count_os_wait = 0;
-	lock->file_name = "not yet reserved";
-	lock->line = 0;
 	lock->last_s_file_name = "not yet reserved";
 	lock->last_x_file_name = "not yet reserved";
 	lock->last_s_line = 0;
@@ -479,12 +475,6 @@ rw_lock_x_lock_wait_func(
 			ut_d(rw_lock_remove_debug_info(
 					lock, pass, RW_LOCK_X_WAIT));
 
-			if (srv_instrument_semaphores) {
-				lock->thread_id = os_thread_get_curr_id();
-				lock->file_name = file_name;
-				lock->line = line;
-			}
-
 			/* It is possible to wake when lock_word < 0.
 			We must pass the while-loop check to proceed.*/
 
@@ -587,13 +577,6 @@ rw_lock_x_lock_low(
 
 	ut_d(rw_lock_add_debug_info(lock, pass, RW_LOCK_X, file_name, line));
 
-
-	if (srv_instrument_semaphores) {
-		lock->thread_id = os_thread_get_curr_id();
-		lock->file_name = file_name;
-		lock->line = line;
-	}
-
 	lock->last_x_file_name = file_name;
 	lock->last_x_line = (unsigned int) line;