10.4-MDEV-29684 Fixes for cluster wide write conflict resolving

If two high priority threads have lock conflict, we look at the order of these transactions and honor the earlier transaction. for_locking parameter in lock_rec_has_to_wait() has become obsolete and it is now removed from the code . Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

Author: sjaakola

sql/service_wsrep.cc

@@ -1,4 +1,4 @@
-/* Copyright 2018-2021 Codership Oy <info@codership.com>
+/* Copyright 2018-2023 Codership Oy <info@codership.com>
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@@ -274,7 +274,9 @@ extern "C" my_bool wsrep_thd_skip_locking(const THD *thd)
 
 extern "C" my_bool wsrep_thd_order_before(const THD *left, const THD *right)
 {
- if (wsrep_thd_trx_seqno(left) < wsrep_thd_trx_seqno(right)) {
+ if (wsrep_thd_is_BF(left, false) &&
+ wsrep_thd_is_BF(right, false) &&
+ wsrep_thd_trx_seqno(left) < wsrep_thd_trx_seqno(right)) {
  WSREP_DEBUG("BF conflict, order: %lld %lld\n",
  (long long)wsrep_thd_trx_seqno(left),
  (long long)wsrep_thd_trx_seqno(right));

sql/sql_class.cc

@@ -5230,8 +5230,6 @@ thd_need_ordering_with(const MYSQL_THD thd, const MYSQL_THD other_thd)
  (e.g. InnoDB does it by keeping lock_sys.mutex locked)
  */
  if (WSREP_ON &&
- wsrep_thd_is_BF(thd, false) &&
- wsrep_thd_is_BF(other_thd, false) &&
  wsrep_thd_order_before(thd, other_thd))
  return 0;
 #endif /* WITH_WSREP */

storage/innobase/lock/lock0lock.cc

@@ -819,25 +819,34 @@ lock_rec_has_to_wait(
 }
 
 #ifdef WITH_WSREP
-/* New lock request from a transaction is using unique key
-scan and this transaction is a wsrep high priority transaction
-(brute force). If conflicting transaction is also wsrep high
-priority transaction we should avoid lock conflict because
-ordering of these transactions is already decided and
-conflicting transaction will be later replayed. Note
-that thread holding conflicting lock can't be
-committed or rolled back while we hold
-lock_sys->mutex. */
-if (trx->is_wsrep_UK_scan()
- && wsrep_thd_is_BF(lock2->trx->mysql_thd, false)) {
-return false;
-}
+/* New lock request from a transaction is using unique key
+scan and this transaction is a wsrep high priority transaction
+(brute force). If conflicting transaction is also wsrep high
+priority transaction we should avoid lock conflict because
+ordering of these transactions is already decided and
+conflicting transaction will be later replayed. Note
+that thread holding conflicting lock can't be
+committed or rolled back while we hold
+lock_sys->mutex. */
+if (trx->is_wsrep_UK_scan()
+ && wsrep_thd_is_BF(lock2->trx->mysql_thd, false)) {
+return false;
+}
 
-/* We very well can let bf to wait normally as other
-BF will be replayed in case of conflict. For debug
-builds we will do additional sanity checks to catch
-unsupported bf wait if any. */
-ut_d(wsrep_assert_no_bf_bf_wait(lock2, trx));
+/* If BF-BF conflict, we have to look at write set order */
+if (trx->is_wsrep()
+ && (type_mode & LOCK_MODE_MASK) == LOCK_X
+ && (lock2->type_mode & LOCK_MODE_MASK) == LOCK_X
+ && wsrep_thd_order_before(trx->mysql_thd,
+ lock2->trx->mysql_thd)) {
+return false;
+}
+
+/* We very well can let bf to wait normally as other
+BF will be replayed in case of conflict. For debug
+builds we will do additional sanity checks to catch
+unsupported bf wait if any. */
+ut_d(wsrep_assert_no_bf_bf_wait(lock2, trx));
 #endif /* WITH_WSREP */
 
 return true;
@@ -2043,6 +2052,14 @@ lock_rec_has_to_wait_in_queue(
 if (heap_no < lock_rec_get_n_bits(lock)
  && (p[bit_offset] & bit_mask)
  && lock_has_to_wait(wait_lock, lock)) {
+#ifdef WITH_WSREP
+if (lock->trx->is_wsrep()
+ && wsrep_thd_order_before(wait_lock->trx->mysql_thd,
+ lock->trx->mysql_thd)) {
+/* don't wait for another BF lock */
+continue;
+}
+#endif
 return(lock);
 }
 }