MDEV-24142: Remove the LatchDebug interface to rw-locks

The latching order checks for rw-locks have not caught many bugs
in the past few years and they are greatly complicating the code.

Last time the debug checks were useful was in
commit 59caf2c (MDEV-13485).

The B-tree hang MDEV-14637 was not caught by LatchDebug,
because the granularity of the checks is not sufficient
to distinguish the levels of non-leaf B-tree pages.

The interface was already made dead code by the grandparent
commit 03ca649.

storage/innobase/btr/btr0btr.cc

@@ -366,8 +366,6 @@ btr_root_adjust_on_import(
 		goto func_exit;
 	}
 
-	buf_block_dbg_add_level(block, SYNC_TREE_NODE);
-
 	page = buf_block_get_frame(block);
 	page_zip = buf_block_get_page_zip(block);
 
@@ -490,8 +488,6 @@ btr_page_alloc_for_ibuf(
 		index->table->space->zip_size(),
 		RW_X_LATCH, mtr);
 
-	buf_block_dbg_add_level(new_block, SYNC_IBUF_TREE_NODE_NEW);
-
 	flst_remove(root, PAGE_HEADER + PAGE_BTR_IBUF_FREE_LIST,
 		    new_block, PAGE_HEADER + PAGE_BTR_IBUF_FREE_LIST_NODE,
 		    mtr);
@@ -557,21 +553,13 @@ btr_page_alloc(
 					for x-latching and initializing
 					the page */
 {
-	buf_block_t*	new_block;
-
 	if (dict_index_is_ibuf(index)) {
 
 		return(btr_page_alloc_for_ibuf(index, mtr));
 	}
 
-	new_block = btr_page_alloc_low(
+	return btr_page_alloc_low(
 		index, hint_page_no, file_direction, level, mtr, init_mtr);
-
-	if (new_block) {
-		buf_block_dbg_add_level(new_block, SYNC_TREE_NODE_NEW);
-	}
-
-	return(new_block);
 }
 
 /**************************************************************//**
@@ -979,8 +967,6 @@ btr_free_root_check(
 		page_id, zip_size, RW_X_LATCH, mtr);
 
 	if (block) {
-		buf_block_dbg_add_level(block, SYNC_TREE_NODE);
-
 		if (fil_page_index_page_check(block->frame)
 		    && index_id == btr_page_get_index_id(block->frame)) {
 			/* This should be a root page.
@@ -1030,9 +1016,6 @@ btr_create(
 			return(FIL_NULL);
 		}
 
-		buf_block_dbg_add_level(
-			ibuf_hdr_block, SYNC_IBUF_TREE_NODE_NEW);
-
 		ut_ad(ibuf_hdr_block->page.id().page_no()
 		      == IBUF_HEADER_PAGE_NO);
 		/* Allocate then the next page to the segment: it will be the
@@ -1050,8 +1033,6 @@ btr_create(
 
 		ut_ad(block->page.id() == page_id_t(0,IBUF_TREE_ROOT_PAGE_NO));
 
-		buf_block_dbg_add_level(block, SYNC_IBUF_TREE_NODE_NEW);
-
 		flst_init(block, PAGE_HEADER + PAGE_BTR_IBUF_FREE_LIST, mtr);
 	} else {
 		block = fseg_create(space, PAGE_HEADER + PAGE_BTR_SEG_TOP,
@@ -1061,19 +1042,13 @@ btr_create(
 			return(FIL_NULL);
 		}
 
-		buf_block_dbg_add_level(block, SYNC_TREE_NODE_NEW);
-
 		if (!fseg_create(space, PAGE_HEADER + PAGE_BTR_SEG_LEAF, mtr,
 				 false, block)) {
 			/* Not enough space for new segment, free root
 			segment before return. */
 			btr_free_root(block, mtr);
 			return(FIL_NULL);
 		}
-
-		/* The fseg create acquires a second latch on the page,
-		therefore we must declare it: */
-		buf_block_dbg_add_level(block, SYNC_TREE_NODE_NEW);
 	}
 
 	ut_ad(!page_has_siblings(block->frame));

storage/innobase/btr/btr0cur.cc

@@ -556,7 +556,6 @@ static dberr_t btr_cur_instant_init_low(dict_index_t* index, mtr_t* mtr)
 			page_id_t(space->id,
 				  mach_read_from_4(ptr + BTR_EXTERN_PAGE_NO)),
 			0, RW_S_LATCH, mtr);
-		buf_block_dbg_add_level(block, SYNC_EXTERN_STORAGE);
 		if (fil_page_get_type(block->frame) != FIL_PAGE_TYPE_BLOB
 		    || mach_read_from_4(&block->frame[FIL_PAGE_DATA
 						      + BTR_BLOB_HDR_NEXT_PAGE_NO])
@@ -1798,17 +1797,13 @@ btr_cur_search_to_nth_level_func(
 		goto search_loop;
 	}
 
-	if (rw_latch != RW_NO_LATCH) {
 #ifdef UNIV_ZIP_DEBUG
+	if (rw_latch != RW_NO_LATCH) {
 		const page_zip_des_t*	page_zip
 			= buf_block_get_page_zip(block);
 		ut_a(!page_zip || page_zip_validate(page_zip, page, index));
-#endif /* UNIV_ZIP_DEBUG */
-
-		buf_block_dbg_add_level(
-			block, dict_index_is_ibuf(index)
-			? SYNC_IBUF_TREE_NODE : SYNC_TREE_NODE);
 	}
+#endif /* UNIV_ZIP_DEBUG */
 
 	ut_ad(fil_page_index_page_check(page));
 	ut_ad(index->id == btr_page_get_index_id(page));
@@ -4402,7 +4397,6 @@ static void btr_cur_trim_alter_metadata(dtuple_t* entry,
 		page_id_t(index->table->space->id,
 			  mach_read_from_4(ptr + BTR_EXTERN_PAGE_NO)),
 		0, RW_S_LATCH, &mtr);
-	buf_block_dbg_add_level(block, SYNC_EXTERN_STORAGE);
 	ut_ad(fil_page_get_type(block->frame) == FIL_PAGE_TYPE_BLOB);
 	ut_ad(mach_read_from_4(&block->frame[FIL_PAGE_DATA
 					     + BTR_BLOB_HDR_NEXT_PAGE_NO])
@@ -7359,9 +7353,6 @@ btr_store_big_rec_extern_fields(
 					rec_block->zip_size(),
 					RW_X_LATCH, &mtr);
 
-				buf_block_dbg_add_level(prev_block,
-							SYNC_EXTERN_STORAGE);
-
 				if (page_zip) {
 					mtr.write<4>(*prev_block,
 						     prev_block->frame
@@ -7680,12 +7671,8 @@ btr_free_externally_stored_field(
 		const page_id_t	page_id(page_get_space_id(p),
 					page_get_page_no(p));
 
-#if 0
-		buf_block_t* rec_block =
-#endif
 		buf_page_get(page_id, rec_zip_size, RW_X_LATCH, &mtr);
 
-		buf_block_dbg_add_level(rec_block, SYNC_NO_ORDER_CHECK);
 		page_no = mach_read_from_4(field_ref + BTR_EXTERN_PAGE_NO);
 
 		if (/* There is no external storage data */
@@ -7712,7 +7699,6 @@ btr_free_externally_stored_field(
 			page_id_t(space_id, page_no), ext_zip_size,
 			RW_X_LATCH, &mtr);
 
-		buf_block_dbg_add_level(ext_block, SYNC_EXTERN_STORAGE);
 		page = buf_block_get_frame(ext_block);
 
 		if (ext_zip_size) {
@@ -7882,7 +7868,6 @@ btr_copy_blob_prefix(
 		mtr_start(&mtr);
 
 		block = buf_page_get(id, 0, RW_S_LATCH, &mtr);
-		buf_block_dbg_add_level(block, SYNC_EXTERN_STORAGE);
 		page = buf_block_get_frame(block);
 
 		btr_check_blob_fil_page_type(*block, true);

storage/innobase/btr/btr0pcur.cc

@@ -338,11 +338,6 @@ btr_pcur_restore_position_func(
 			cursor->pos_state = BTR_PCUR_IS_POSITIONED;
 			cursor->latch_mode = latch_mode;
 
-			buf_block_dbg_add_level(
-				btr_pcur_get_block(cursor),
-				dict_index_is_ibuf(index)
-				? SYNC_IBUF_TREE_NODE : SYNC_TREE_NODE);
-
 			if (cursor->rel_pos == BTR_PCUR_ON) {
 #ifdef UNIV_DEBUG
 				const rec_t*	rec;

storage/innobase/btr/btr0sea.cc

@@ -1120,7 +1120,6 @@ btr_search_guess_on_hash(
 
 		part->latch.rd_unlock();
 
-		buf_block_dbg_add_level(block, SYNC_TREE_NODE_FROM_HASH);
 		if (UNIV_UNLIKELY(fail)) {
 			goto fail_and_release_page;
 		}
@@ -1390,7 +1389,6 @@ void btr_search_drop_page_hash_when_freed(const page_id_t page_id)
 {
 	buf_block_t*	block;
 	mtr_t		mtr;
-	dberr_t		err = DB_SUCCESS;
 
 	mtr_start(&mtr);
 
@@ -1402,18 +1400,14 @@ void btr_search_drop_page_hash_when_freed(const page_id_t page_id)
 
 	block = buf_page_get_gen(page_id, 0, RW_X_LATCH, NULL,
 				 BUF_PEEK_IF_IN_POOL, __FILE__, __LINE__,
-				 &mtr, &err);
+				 &mtr);
 
 	if (block) {
-
 		/* If AHI is still valid, page can't be in free state.
 		AHI is dropped when page is freed. */
 		DBUG_ASSERT(block->page.status != buf_page_t::FREED);
 
-		buf_block_dbg_add_level(block, SYNC_TREE_NODE_FROM_HASH);
-
-		dict_index_t*	index = block->index;
-		if (index != NULL) {
+		if (block->index) {
 			/* In all our callers, the table handle should
 			be open, or we should be in the process of
 			dropping the table (preventing eviction). */

storage/innobase/buf/buf0buf.cc

@@ -2505,7 +2505,6 @@ void buf_page_free(const page_id_t page_id, mtr_t *mtr)
   block->lock.x_lock();
 
   block->page.status= buf_page_t::FREED;
-  buf_block_dbg_add_level(block, SYNC_NO_ORDER_CHECK);
   hash_lock->read_unlock();
 }
 
@@ -3417,9 +3416,6 @@ buf_page_optimistic_get(
 	}
 
 	if (modify_clock != block->modify_clock) {
-
-		buf_block_dbg_add_level(block, SYNC_NO_ORDER_CHECK);
-
 		if (rw_latch == RW_S_LATCH) {
 			block->lock.s_unlock();
 		} else {
@@ -3494,7 +3490,6 @@ buf_page_try_get_func(
   ut_ad(bpage->buf_fix_count());
   ut_ad(bpage->state() == BUF_BLOCK_FILE_PAGE);
   ut_ad(bpage->id() == page_id);
-  buf_block_dbg_add_level(block, SYNC_NO_ORDER_CHECK);
 
   buf_pool.stat.n_page_gets++;
   return block;

storage/innobase/buf/buf0dblwr.cc

@@ -43,10 +43,8 @@ buf_dblwr_t buf_dblwr;
 /** @return the TRX_SYS page */
 inline buf_block_t *buf_dblwr_trx_sys_get(mtr_t *mtr)
 {
-  buf_block_t *block= buf_page_get(page_id_t(TRX_SYS_SPACE, TRX_SYS_PAGE_NO),
-                                   0, RW_X_LATCH, mtr);
-  buf_block_dbg_add_level(block, SYNC_NO_ORDER_CHECK);
-  return block;
+  return buf_page_get(page_id_t(TRX_SYS_SPACE, TRX_SYS_PAGE_NO),
+                      0, RW_X_LATCH, mtr);
 }
 
 /** Initialize the doublewrite buffer data structure.
@@ -121,10 +119,6 @@ bool buf_dblwr_t::create()
     the InnoDB system tablespace file in the first place.
     It could be located in separate optional file(s) in a
     user-specified location. */
-
-    /* fseg_create acquires a second latch on the page,
-    therefore we must declare it: */
-    buf_block_dbg_add_level(b, SYNC_NO_ORDER_CHECK);
   }
 
   byte *fseg_header= TRX_SYS_DOUBLEWRITE + TRX_SYS_DOUBLEWRITE_FSEG +

storage/innobase/dict/dict0boot.cc

@@ -35,15 +35,6 @@ Created 4/18/1996 Heikki Tuuri
 #include "log0recv.h"
 #include "os0file.h"
 
-/** @return the DICT_HDR block, x-latched */
-buf_block_t *dict_hdr_get(mtr_t* mtr)
-{
-  buf_block_t *block= buf_page_get(page_id_t(DICT_HDR_SPACE, DICT_HDR_PAGE_NO),
-				   0, RW_X_LATCH, mtr);
-  buf_block_dbg_add_level(block, SYNC_DICT_HEADER);
-  return block;
-}
-
 /**********************************************************************//**
 Returns a new table, index, or space id. */
 void

storage/innobase/fsp/fsp0fsp.cc

@@ -129,7 +129,6 @@ inline buf_block_t *fsp_get_header(const fil_space_t *space, mtr_t *mtr)
 {
  buf_block_t *block= buf_page_get(page_id_t(space->id, 0), space->zip_size(),
                                   RW_SX_LATCH, mtr);
- buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
  ut_ad(space->id == mach_read_from_4(FSP_HEADER_OFFSET + FSP_SPACE_ID +
                                      block->frame));
  return block;
@@ -349,8 +348,6 @@ xdes_get_descriptor_with_space_hdr(
 		block = buf_page_get(
 			page_id_t(space->id, descr_page_no), zip_size,
 			RW_SX_LATCH, mtr);
-
-		buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
 	}
 
 	if (desc_block != NULL) {
@@ -379,7 +376,6 @@ static xdes_t* xdes_get_descriptor(const fil_space_t *space, page_no_t offset,
 {
   buf_block_t *block= buf_page_get(page_id_t(space->id, 0), space->zip_size(),
                                    RW_SX_LATCH, mtr);
-  buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
   return xdes_get_descriptor_with_space_hdr(block, space, offset, xdes, mtr);
 }
 
@@ -412,8 +408,6 @@ xdes_get_descriptor_const(
 
 	if (buf_block_t* block = buf_page_get(page_id_t(space->id, page),
 					      zip_size, RW_S_LATCH, mtr)) {
-		buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
-
 		ut_ad(page != 0 || space->free_limit == mach_read_from_4(
 			      FSP_FREE_LIMIT + FSP_HEADER_OFFSET
 			      + block->frame));
@@ -553,8 +547,6 @@ void fsp_header_init(fil_space_t* space, uint32_t size, mtr_t* mtr)
 
 	buf_block_t* block = buf_page_create(space, 0, zip_size, mtr,
 					     free_block);
-	buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
-
 	if (UNIV_UNLIKELY(block != free_block)) {
 		buf_pool.free_block(free_block);
 	}
@@ -877,7 +869,6 @@ fsp_fill_free_list(
 				block= buf_page_create(
 					space, static_cast<uint32_t>(i),
 					zip_size, mtr, f);
-				buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
 				if (UNIV_UNLIKELY(block != f)) {
 					buf_pool.free_block(f);
 				}
@@ -894,7 +885,6 @@ fsp_fill_free_list(
 					static_cast<uint32_t>(
 						i + FSP_IBUF_BITMAP_OFFSET),
 					zip_size, mtr, f);
-				buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
 				if (UNIV_UNLIKELY(block != f)) {
 					buf_pool.free_block(f);
 				}
@@ -1357,7 +1347,6 @@ fsp_alloc_seg_inode_page(fil_space_t *space, buf_block_t *header, mtr_t *mtr)
   if (!block)
     return false;
 
-  buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
   ut_ad(block->lock.not_recursive());
 
   mtr->write<2>(*block, block->frame + FIL_PAGE_TYPE, FIL_PAGE_INODE);
@@ -1401,7 +1390,6 @@ fsp_alloc_seg_inode(fil_space_t *space, buf_block_t *header,
 			       + header->frame).page);
 
 	block = buf_page_get(page_id, space->zip_size(), RW_SX_LATCH, mtr);
-	buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
 	if (!space->full_crc32()) {
 		fil_block_check_type(*block, FIL_PAGE_INODE, mtr);
 	}

storage/innobase/gis/gis0sea.cc

@@ -268,8 +268,6 @@ rtr_pcur_getnext_from_path(
 
 		if (block == NULL) {
 			continue;
-		} else if (rw_latch != RW_NO_LATCH) {
-			buf_block_dbg_add_level(block, SYNC_TREE_NODE);
 		}
 
 		rtr_info->tree_blocks[tree_idx] = block;

storage/innobase/handler/ha_innodb.cc

@@ -534,9 +534,6 @@ static PSI_mutex_info all_innodb_mutexes[] = {
 	PSI_KEY(recv_sys_mutex),
 	PSI_KEY(redo_rseg_mutex),
 	PSI_KEY(noredo_rseg_mutex),
-#  ifdef UNIV_DEBUG
-	PSI_KEY(rw_lock_debug_mutex),
-#  endif /* UNIV_DEBUG */
 	PSI_KEY(srv_innodb_monitor_mutex),
 	PSI_KEY(srv_misc_tmpfile_mutex),
 	PSI_KEY(srv_monitor_file_mutex),