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Commit 1904b11b authored by Aleksey Midenkov's avatar Aleksey Midenkov
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MDEV-18706 ER_LOCK_DEADLOCK on concurrent read and insert into already locked gap 

* Cause
No real deadlock, but incomplete conflict detection:

1. Con1-X blocks on Def-X lock (p.2 in test);
2. Def-II-X has to wait Con1-X and here conflict resolution starts (p.3 in test);
3. Conflict resolution goes through a tree of locks:
  a. (Def-II-X, Def-X): ok
  b. (Def-II-X, Con1-X): conflict, traversing from Con1-X
  c. (Con1-X, Def-X): conflict, found cycle (because resolution started from Def).

The weak point here is 2. (lock_rec_has_to_wait()), because Def-II-X
doesn't have to wait Con1: Def already got X "next-key" lock that also
holds the gap before the record.

* Fix
Allow lock in `lock_rec_other_has_conflicting()` if there is already
non-waiting stronger or equal lock in this transaction
(`lock_rec_has_expl()`).

row_search_mvcc(): SELECT FOR UPDATE skips inserted records when
next-key lock is released. Fixed by stepping back before wait and
stepping forward before acquire: it steps into the gap again and
discovers newly inserted records. Note that change to row_sel() is not
required as it is used for internal queries only.

* Test fixes
innodb.auto_increment_dup: log-bin behaves like skip-log-bin because
of no bogus deadlock on UPDATE.

versioning.update: originally described deadlock from this task is now
disappeared.
parent 9dedba16
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Showing with 362 additions and 30 deletions
mysql-test/suite/innodb/r/innodb-lock.result
View file @ 1904b11b
......@@ -159,3 +159,152 @@ connection con1;
disconnect con1;
connection default;
DROP TABLE t1, t2, t3;
#
# MDEV-18706 ER_LOCK_DEADLOCK on concurrent read and insert into already locked gap
#
# A) Def inserts between infimum and Def-locked record, between Def-locked record and supremum
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (3, 0);
start transaction;
update t1 set x= 1;
connect con1, localhost, root,, test;
select * from t1 for update;
connection default;
insert into t1 values (1, 1);
insert into t1 values (2, 1);
insert into t1 values (4, 1);
insert into t1 values (5, 1);
commit;
connection con1;
# No ER_LOCK_DEADLOCK; all rows returned
pk x
1 1
2 1
3 1
4 1
5 1
connection default;
disconnect con1;
drop table t1;
# B) Def inserts between Con1-locked and Def-locked record
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (1, 2);
insert into t1 values (4, 0);
start transaction;
update t1 set x= 2 where pk > 3;
connect con1,localhost,root,,test;
select * from t1 for update;
connection default;
insert into t1 values (2, 2);
insert into t1 values (3, 2);
insert into t1 values (5, 2);
commit;
connection con1;
# No ER_LOCK_DEADLOCK; all rows returned
pk x
1 2
2 2
3 2
4 2
5 2
connection default;
disconnect con1;
drop table t1;
# C) Same as A) but reverse direction
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (3, 0);
start transaction;
update t1 set x= 3;
connect con1,localhost,root,,test;
select * from t1 order by pk desc for update;
connection default;
insert into t1 values (1, 3);
insert into t1 values (2, 3);
insert into t1 values (4, 3);
insert into t1 values (5, 3);
commit;
connection con1;
# No ER_LOCK_DEADLOCK; all rows returned
pk x
5 3
4 3
3 3
2 3
1 3
connection default;
disconnect con1;
drop table t1;
# D) Same as B) but reverse direction
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (2, 0);
insert into t1 values (5, 4);
start transaction;
update t1 set x= 4 where pk < 3;
connect con1,localhost,root,,test;
select * from t1 order by pk desc for update;
connection default;
insert into t1 values (1, 4);
insert into t1 values (3, 4);
insert into t1 values (4, 4);
commit;
connection con1;
# No ER_LOCK_DEADLOCK; all rows returned
pk x
5 4
4 4
3 4
2 4
1 4
connection default;
disconnect con1;
drop table t1;
# E) Same as A) but UPDATE instead SELECT
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (3, 0);
start transaction;
update t1 set x= 5;
connect con1, localhost, root,, test;
update t1 set x= x + 10;
connection default;
insert into t1 values (1, 5);
insert into t1 values (2, 5);
insert into t1 values (4, 5);
insert into t1 values (5, 5);
commit;
connection con1;
# No ER_LOCK_DEADLOCK; all rows returned
connection default;
select * from t1;
pk x
1 15
2 15
3 15
4 15
5 15
disconnect con1;
drop table t1;
# F) Same as B) but UPDATE instead SELECT
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (1, 6);
insert into t1 values (4, 0);
start transaction;
update t1 set x= 6 where pk > 3;
connect con1,localhost,root,,test;
update t1 set x= x + 10;
connection default;
insert into t1 values (2, 6);
insert into t1 values (3, 6);
insert into t1 values (5, 6);
commit;
connection con1;
# No ER_LOCK_DEADLOCK; all rows returned
connection default;
select * from t1;
pk x
1 16
2 16
3 16
4 16
5 16
disconnect con1;
drop table t1;
mysql-test/suite/innodb/t/innodb-lock.opt 0 → 100644
View file @ 1904b11b
--enable-plugin-innodb-lock-waits
mysql-test/suite/innodb/t/innodb-lock.test
View file @ 1904b11b
......@@ -219,3 +219,150 @@ reap;
disconnect con1;
connection default;
DROP TABLE t1, t2, t3;
--echo #
--echo # MDEV-18706 ER_LOCK_DEADLOCK on concurrent read and insert into already locked gap
--echo #
--echo # A) Def inserts between infimum and Def-locked record, between Def-locked record and supremum
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (3, 0);
start transaction;
# 1. Def: X-lock "3" as "next key" (row + gap)
update t1 set x= 1;
connect (con1, localhost, root,, test);
# 2. Con1: Block on "3"
send select * from t1 for update;
connection default;
--let $wait_condition= select count(*) from information_schema.innodb_lock_waits
--source include/wait_condition.inc
# 3. Def: Insert before and after "3"
insert into t1 values (1, 1);
insert into t1 values (2, 1);
insert into t1 values (4, 1);
insert into t1 values (5, 1);
# 4. Def: Unlock "3"
commit;
connection con1;
# 5. Con1: Continue SELECT
--echo # No ER_LOCK_DEADLOCK; all rows returned
reap;
connection default;
disconnect con1;
drop table t1;
--echo # B) Def inserts between Con1-locked and Def-locked record
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (1, 2);
insert into t1 values (4, 0);
start transaction;
# 1. Def: X-lock "4" as "next key" (row + gap)
update t1 set x= 2 where pk > 3;
connect (con1,localhost,root,,test);
# 2. Con1: X-lock "1", block on "4"
send select * from t1 for update;
connection default;
--let $wait_condition= select count(*) from information_schema.innodb_lock_waits
--source include/wait_condition.inc
# 3. Def: Insert before and after "4"
# Note: we cannot INSERT before "1" because Con1 already X-locked it
insert into t1 values (2, 2);
insert into t1 values (3, 2);
insert into t1 values (5, 2);
commit;
connection con1;
--echo # No ER_LOCK_DEADLOCK; all rows returned
reap;
connection default;
disconnect con1;
drop table t1;
--echo # C) Same as A) but reverse direction
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (3, 0);
start transaction;
update t1 set x= 3;
connect (con1,localhost,root,,test);
send select * from t1 order by pk desc for update;
connection default;
--let $wait_condition= select count(*) from information_schema.innodb_lock_waits
--source include/wait_condition.inc
insert into t1 values (1, 3);
insert into t1 values (2, 3);
insert into t1 values (4, 3);
insert into t1 values (5, 3);
commit;
connection con1;
--echo # No ER_LOCK_DEADLOCK; all rows returned
reap;
connection default;
disconnect con1;
drop table t1;
--echo # D) Same as B) but reverse direction
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (2, 0);
insert into t1 values (5, 4);
start transaction;
update t1 set x= 4 where pk < 3;
connect (con1,localhost,root,,test);
send select * from t1 order by pk desc for update;
connection default;
--let $wait_condition= select count(*) from information_schema.innodb_lock_waits
--source include/wait_condition.inc
insert into t1 values (1, 4);
insert into t1 values (3, 4);
insert into t1 values (4, 4);
commit;
connection con1;
--echo # No ER_LOCK_DEADLOCK; all rows returned
reap;
connection default;
disconnect con1;
drop table t1;
--echo # E) Same as A) but UPDATE instead SELECT
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (3, 0);
start transaction;
update t1 set x= 5;
connect (con1, localhost, root,, test);
send update t1 set x= x + 10;
connection default;
--let $wait_condition= select count(*) from information_schema.innodb_lock_waits
--source include/wait_condition.inc
insert into t1 values (1, 5);
insert into t1 values (2, 5);
insert into t1 values (4, 5);
insert into t1 values (5, 5);
commit;
connection con1;
--echo # No ER_LOCK_DEADLOCK; all rows returned
reap;
connection default;
select * from t1;
disconnect con1;
drop table t1;
--echo # F) Same as B) but UPDATE instead SELECT
create or replace table t1 (pk int primary key, x int) engine innodb;
insert into t1 values (1, 6);
insert into t1 values (4, 0);
start transaction;
update t1 set x= 6 where pk > 3;
connect (con1,localhost,root,,test);
send update t1 set x= x + 10;
connection default;
--let $wait_condition= select count(*) from information_schema.innodb_lock_waits
--source include/wait_condition.inc
insert into t1 values (2, 6);
insert into t1 values (3, 6);
insert into t1 values (5, 6);
commit;
connection con1;
--echo # No ER_LOCK_DEADLOCK; all rows returned
reap;
connection default;
select * from t1;
disconnect con1;
drop table t1;
storage/innobase/include/lock0priv.h
View file @ 1904b11b
......@@ -685,6 +685,25 @@ inline void lock_reset_lock_and_trx_wait(lock_t* lock)
lock->type_mode &= ~LOCK_WAIT;
}
inline
bool ib_lock_t::is_stronger(ulint precise_mode, ulint heap_no, const trx_t* t) const
{
ut_ad(is_record_lock());
return trx == t
&& !is_waiting()
&& !is_insert_intention()
&& (!is_record_not_gap()
|| (precise_mode & LOCK_REC_NOT_GAP) /* only record */
|| heap_no == PAGE_HEAP_NO_SUPREMUM)
&& (!is_gap()
|| (precise_mode & LOCK_GAP) /* only gap */
|| heap_no == PAGE_HEAP_NO_SUPREMUM)
&& lock_mode_stronger_or_eq(
mode(),
static_cast<lock_mode>(
precise_mode & LOCK_MODE_MASK));
}
#include "lock0priv.ic"
#endif /* lock0priv_h */
storage/innobase/include/lock0types.h
View file @ 1904b11b
......@@ -237,7 +237,10 @@ struct ib_lock_t
return(type_mode & LOCK_INSERT_INTENTION);
}
ulint type() const {
bool is_stronger(ulint precise_mode, ulint heap_no, const trx_t* t) const;
ulint type() const
{
return(type_mode & LOCK_TYPE_MASK);
}
......
storage/innobase/lock/lock0lock.cc
View file @ 1904b11b
......@@ -1022,19 +1022,7 @@ lock_rec_has_expl(
lock != NULL;
lock = lock_rec_get_next(heap_no, lock)) {
if (lock->trx == trx
&& !lock_rec_get_insert_intention(lock)
&& lock_mode_stronger_or_eq(
lock_get_mode(lock),
static_cast<lock_mode>(
precise_mode & LOCK_MODE_MASK))
&& !lock_get_wait(lock)
&& (!lock_rec_get_rec_not_gap(lock)
|| (precise_mode & LOCK_REC_NOT_GAP)
|| heap_no == PAGE_HEAP_NO_SUPREMUM)
&& (!lock_rec_get_gap(lock)
|| (precise_mode & LOCK_GAP)
|| heap_no == PAGE_HEAP_NO_SUPREMUM)) {
if (lock->is_stronger(precise_mode, heap_no, trx)) {
return(lock);
}
......@@ -1165,39 +1153,47 @@ lock_rec_other_has_conflicting(
/*===========================*/
ulint mode, /*!< in: LOCK_S or LOCK_X,
possibly ORed to LOCK_GAP or
LOC_REC_NOT_GAP,
LOCK_REC_NOT_GAP,
LOCK_INSERT_INTENTION */
const buf_block_t* block, /*!< in: buffer block containing
the record */
ulint heap_no,/*!< in: heap number of the record */
const trx_t* trx) /*!< in: our transaction */
{
lock_t* lock;
lock_t* res = NULL;
ut_ad(lock_mutex_own());
bool is_supremum = (heap_no == PAGE_HEAP_NO_SUPREMUM);
for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
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_has_to_wait(true, trx, mode, lock, is_supremum)) {
#ifdef WITH_WSREP
if (trx->is_wsrep()) {
trx_mutex_enter(lock->trx);
/* Below function will roll back either trx
or lock->trx depending on priority of the
transaction. */
wsrep_kill_victim(const_cast<trx_t*>(trx), lock);
trx_mutex_exit(lock->trx);
}
#endif /* WITH_WSREP */
return(lock);
/* If current trx already acquired a lock not weaker covering
same types then we don't have to wait for any locks. */
if (lock->is_stronger(mode, heap_no, trx)) {
return(NULL);
}
if (!res && lock_rec_has_to_wait(true, trx, mode, lock, is_supremum)) {
res = lock;
}
}
return(NULL);
#ifdef WITH_WSREP
if (res && trx->is_wsrep()) {
trx_mutex_enter(res->trx);
/* Below function will roll back either trx
or lock->trx depending on priority of the
transaction. */
wsrep_kill_victim(const_cast<trx_t*>(trx), res);
trx_mutex_exit(res->trx);
}
#endif /* WITH_WSREP */
return(res);
}
/*********************************************************************//**
......
storage/innobase/row/row0sel.cc
View file @ 1904b11b
......@@ -5733,6 +5733,13 @@ row_search_mvcc(
lock_wait_or_error:
if (!dict_index_is_spatial(index)) {
/* Locked gap may be filled with inserted records.
Make sure we don't miss them. */
if (moves_up) {
btr_pcur_move_to_prev(pcur, &mtr);
} else {
btr_pcur_move_to_next(pcur, &mtr);
}
btr_pcur_store_position(pcur, &mtr);
}
page_read_error:
......@@ -5775,6 +5782,16 @@ row_search_mvcc(
sel_restore_position_for_mysql(
&same_user_rec, BTR_SEARCH_LEAF, pcur,
moves_up, &mtr);
/* Counterpart of the stepping backward in lock_wait_or_error.
This is linked tight with that btr_pcur_store_position().
The jumps to page_read_error: and lock_table_wait: do not get here. */
if (same_user_rec) {
if (!moves_up) {
btr_pcur_move_to_prev(pcur, &mtr);
} else {
btr_pcur_move_to_next(pcur, &mtr);
}
}
}
if ((srv_locks_unsafe_for_binlog
......
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