MDEV-28709 unexpected X lock on Supremum in READ COMMITTED

The lock is created during page splitting after moving records and
locks(lock_move_rec_list_(start|end)()) to the new page, and inheriting
the locks to the supremum of left page from the successor of the infimum
on right page.

There is no need in such inheritance for READ COMMITTED isolation level
and not-gap locks, so the fix is to add the corresponding condition in
gap lock inheritance function.

One more fix is to forbid gap lock inheritance if XA was prepared. Use the
most significant bit of trx_t::n_ref to indicate that gap lock inheritance
is forbidden. This fix is based on
mysql/mysql-server@b063e52a8367dc9d5ed418e7f6d96400867e9f43

1 files changed, 53 insertions, 41 deletions

diff --git a/storage/innobase/lock/lock0lock.cc b/storage/innobase/lock/lock0lock.cc
index 380f9201ef5..da009ada289 100644
--- a/storage/innobase/lock/lock0lock.cc
+++ b/storage/innobase/lock/lock0lock.cc
@@ -2291,50 +2291,54 @@ lock_rec_reset_and_release_wait(
 		&lock_sys.prdt_page_hash, block, PAGE_HEAP_NO_INFIMUM);
 }
 
-/*************************************************************//**
-Makes a record to inherit the locks (except LOCK_INSERT_INTENTION type)
+/** Makes a record to inherit the locks (except LOCK_INSERT_INTENTION type)
 of another record as gap type locks, but does not reset the lock bits of
 the other record. Also waiting lock requests on rec are inherited as
-GRANTED gap locks. */
-static
-void
-lock_rec_inherit_to_gap(
-/*====================*/
-	const buf_block_t*	heir_block,	/*!< in: block containing the
-						record which inherits */
-	const buf_block_t*	block,		/*!< in: block containing the
-						record from which inherited;
-						does NOT reset the locks on
-						this record */
-	ulint			heir_heap_no,	/*!< in: heap_no of the
-						inheriting record */
-	ulint			heap_no)	/*!< in: heap_no of the
-						donating record */
+GRANTED gap locks.
+@param heir_block   block containing the record which inherits
+@param block block  containing the record from which inherited; does NOT reset
+                    the locks on this record
+@param heir_heap_no heap_no of the inheriting record
+@param heap_no      heap_no of the donating record
+@tparam from_split  true if the function is invoked from
+                    lock_update_split_(left|right)(), in this case not-gap
+                    locks are not inherited to supremum if transaction
+                    isolation level less or equal to READ COMMITTED */
+template <bool from_split= false>
+static void lock_rec_inherit_to_gap(const buf_block_t *heir_block,
+                                    const buf_block_t *block,
+                                    ulint heir_heap_no, ulint heap_no)
 {
-	lock_t*	lock;
-
-	ut_ad(lock_mutex_own());
+  ut_ad(lock_mutex_own());
+  ut_ad(!from_split || heir_heap_no == PAGE_HEAP_NO_SUPREMUM);
 
-	/* At READ UNCOMMITTED or READ COMMITTED isolation level,
-	we do not want locks set
-	by an UPDATE or a DELETE to be inherited as gap type locks. But we
-	DO want S-locks/X-locks(taken for replace) set by a consistency
-	constraint to be inherited also then. */
+  /* At READ UNCOMMITTED or READ COMMITTED isolation level,
+  we do not want locks set
+  by an UPDATE or a DELETE to be inherited as gap type locks. But we
+  DO want S-locks/X-locks(taken for replace) set by a consistency
+  constraint to be inherited also then. */
 
-	for (lock = lock_rec_get_first(&lock_sys.rec_hash, block, heap_no);
-	     lock != NULL;
-	     lock = lock_rec_get_next(heap_no, lock)) {
+  for (lock_t *lock= lock_rec_get_first(&lock_sys.rec_hash, block, heap_no);
+       lock != NULL; lock= lock_rec_get_next(heap_no, lock))
+  {
 
-		if (!lock_rec_get_insert_intention(lock)
-		    && (lock->trx->isolation_level > TRX_ISO_READ_COMMITTED
-			|| lock_get_mode(lock) !=
-			(lock->trx->duplicates ? LOCK_S : LOCK_X))) {
-			lock_rec_add_to_queue(
-				LOCK_REC | LOCK_GAP | lock_get_mode(lock),
-				heir_block, heir_heap_no, lock->index,
-				lock->trx, FALSE);
-		}
-	}
+    if (!lock->trx->is_not_inheriting_locks() &&
+        !lock_rec_get_insert_intention(lock) &&
+        (lock->trx->isolation_level > TRX_ISO_READ_COMMITTED ||
+         /* When we are in a page split (not purge), then we don't set a lock
+         on supremum if the donor lock type is LOCK_REC_NOT_GAP. That is, do
+         not create bogus gap locks for non-gap locks for READ UNCOMMITTED and
+         READ COMMITTED isolation levels. LOCK_ORDINARY and
+         LOCK_GAP require a gap before the record to be locked, that is why
+         setting lock on supremmum is necessary. */
+         ((!from_split || !lock->is_record_not_gap()) &&
+          (lock_get_mode(lock) != (lock->trx->duplicates ? LOCK_S : LOCK_X)))))
+    {
+      lock_rec_add_to_queue(LOCK_REC | LOCK_GAP | lock_get_mode(lock),
+                            heir_block, heir_heap_no, lock->index, lock->trx,
+                            FALSE);
+    }
+  }
 }
 
 /*************************************************************//**
@@ -2361,7 +2365,8 @@ lock_rec_inherit_to_gap_if_gap_lock(
 	     lock != NULL;
 	     lock = lock_rec_get_next(heap_no, lock)) {
 
-		if (!lock_rec_get_insert_intention(lock)
+		if (!lock->trx->is_not_inheriting_locks()
+		    && !lock_rec_get_insert_intention(lock)
 		    && (heap_no == PAGE_HEAP_NO_SUPREMUM
 			|| !lock_rec_get_rec_not_gap(lock))) {
 
@@ -2943,7 +2948,7 @@ lock_update_split_right(
 	/* Inherit the locks to the supremum of left page from the successor
 	of the infimum on right page */
 
-	lock_rec_inherit_to_gap(left_block, right_block,
+	lock_rec_inherit_to_gap<true>(left_block, right_block,
 				PAGE_HEAP_NO_SUPREMUM, heap_no);
 
 	lock_mutex_exit();
@@ -3063,7 +3068,7 @@ lock_update_split_left(
 	/* Inherit the locks to the supremum of the left page from the
 	successor of the infimum on the right page */
 
-	lock_rec_inherit_to_gap(left_block, right_block,
+	lock_rec_inherit_to_gap<true>(left_block, right_block,
 				PAGE_HEAP_NO_SUPREMUM, heap_no);
 
 	lock_mutex_exit();
@@ -4251,6 +4256,11 @@ void lock_release_on_prepare(trx_t *trx)
       {
         ut_ad(trx->dict_operation ||
               lock->index->table->id >= DICT_HDR_FIRST_ID);
+        ut_ad(lock->trx->isolation_level > TRX_ISO_READ_COMMITTED ||
+              /* Insert-intention lock is valid for supremum for isolation
+              level > TRX_ISO_READ_COMMITTED */
+              lock_get_mode(lock) == LOCK_X ||
+              !lock_rec_get_nth_bit(lock, PAGE_HEAP_NO_SUPREMUM));
 retain_lock:
         lock= UT_LIST_GET_PREV(trx_locks, lock);
         continue;
@@ -4287,6 +4297,8 @@ retain_lock:
   }
 
   lock_mutex_exit();
+
+  trx->set_skip_lock_inheritance();
 }
 
 /* True if a lock mode is S or X */