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MDEV-28709 unexpected X lock on Supremum in READ COMMITTED

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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@b063e52a83
This commit is contained in:
Vlad Lesin 2022-06-29 17:03:56 +03:00
commit 8128a46827
5 changed files with 207 additions and 57 deletions
Download patch file Download diff file Expand all files Collapse all files

94
storage/innobase/lock/lock0lock.cc
View file

@ -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(!from_split || heir_heap_no == PAGE_HEAP_NO_SUPREMUM);
ut_ad(lock_mutex_own());
/* 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_t *lock= lock_rec_get_first(&lock_sys.rec_hash, block, heap_no);
lock != NULL; lock= lock_rec_get_next(heap_no, lock))
{
for (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 */