MDEV-24671 fixup: Remove srv_max_n_threads

The variable srv_max_n_threads lost its usefulness in
commit db006a9a (MDEV-21452)
and commit e71e6133 (MDEV-24671).

extra/mariabackup/backup_copy.cc

@@ -1893,8 +1893,6 @@ copy_back()
 		return(false);
 	}
 
-	srv_max_n_threads = 1000;
-
 	/* copy undo tablespaces */
 
 	Copy_back_dst_dir dst_dir_buf;
@@ -2172,8 +2170,6 @@ decrypt_decompress()
 	bool ret;
 	datadir_iter_t *it = NULL;
 
-	srv_max_n_threads = 1000;
-
 	/* cd to backup directory */
 	if (my_setwd(xtrabackup_target_dir, MYF(MY_WME)))
 	{

extra/mariabackup/xtrabackup.cc

@@ -4714,22 +4714,6 @@ static bool xtrabackup_backup_func()
 		return(false);
 	}
 
-	if (srv_buf_pool_size >= 1000 * 1024 * 1024) {
-                                  /* Here we still have srv_pool_size counted
-                                  in kilobytes (in 4.0 this was in bytes)
-				  srv_boot() converts the value to
-                                  pages; if buffer pool is less than 1000 MB,
-                                  assume fewer threads. */
-                srv_max_n_threads = 50000;
-
-	} else if (srv_buf_pool_size >= 8 * 1024 * 1024) {
-
-                srv_max_n_threads = 10000;
-        } else {
-		srv_max_n_threads = 1000;       /* saves several MB of memory,
-                                                especially in 64-bit
-                                                computers */
-        }
 	srv_thread_pool_init();
 	/* Reset the system variables in the recovery module. */
 	trx_pool_init();
@@ -6166,7 +6150,6 @@ static bool xtrabackup_prepare_func(char** argv)
 		return(false);
 	}
 
-	srv_max_n_threads = 1000;
 	srv_n_purge_threads = 1;
 
 	xb_filters_init();

storage/innobase/include/srv0srv.h

@@ -174,10 +174,6 @@ struct srv_stats_t
 	ulint_ctr_n_t		n_temp_blocks_decrypted;
 };
 
-/** We are prepared for a situation that we have this many threads waiting for
-a transactional lock inside InnoDB. srv_start() sets the value. */
-extern ulint srv_max_n_threads;
-
 extern const char*	srv_main_thread_op_info;
 
 /** Prefix used by MySQL to indicate pre-5.1 table name encoding */

storage/innobase/srv/srv0start.cc

@@ -92,10 +92,6 @@ Created 2/16/1996 Heikki Tuuri
 #include "ut0crc32.h"
 #include "log.h"
 
-/** We are prepared for a situation that we have this many threads waiting for
-a transactional lock inside InnoDB. srv_start() sets the value. */
-ulint srv_max_n_threads;
-
 /** Log sequence number at shutdown */
 lsn_t	srv_shutdown_lsn;
 
@@ -1127,12 +1123,6 @@ dberr_t srv_start(bool create_new_db)
 	mysql_stage_register("innodb", srv_stages,
 			     static_cast<int>(UT_ARR_SIZE(srv_stages)));
 
-	srv_max_n_threads =
-		1 /* dict_stats_thread */
-		+ 1 /* fts_optimize_thread */
-		+ 128 /* safety margin */
-		+ max_connections;
-
 	srv_boot();
 
 	ib::info() << my_crc32c_implementation();