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mariadb/sql/wsrep_dummy.cc
sjaakola 7bffe468b2 MDEV-21910 Deadlock between BF abort and manual KILL command
When high priority replication slave applier encounters lock conflict in innodb,
it will force the conflicting lock holder transaction (victim) to rollback.
This is a must in multi-master sychronous replication model to avoid cluster lock-up.
This high priority victim abort (aka "brute force" (BF) abort), is started
from innodb lock manager while holding the victim's transaction's (trx) mutex.
Depending on the execution state of the victim transaction, it may happen that the
BF abort will call for THD::awake() to wake up the victim transaction for the rollback.
Now, if BF abort requires THD::awake() to be called, then the applier thread executed
locking protocol of: victim trx mutex -> victim THD::LOCK_thd_data

If, at the same time another DBMS super user issues KILL command to abort the same victim,
it will execute locking protocol of: victim THD::LOCK_thd_data  -> victim trx mutex.
These two locking protocol acquire mutexes in opposite order, hence unresolvable mutex locking
deadlock may occur.

The fix in this commit adds THD::wsrep_aborter flag to synchronize who can kill the victim
This flag is set both when BF is called for from innodb and by KILL command.
Either path of victim killing will bail out if victim's wsrep_killed is already
set to avoid mutex conflicts with the other aborter execution. THD::wsrep_aborter
records the aborter THD's ID. This is needed to preserve the right to kill
the victim from different locations for the same aborter thread.
It is also good error logging, to see who is reponsible for the abort.

A new test case was added in galera.galera_bf_kill_debug.test for scenario where
wsrep applier thread and manual KILL command try to kill same idle victim
2020-07-22 08:20:10 +03:00

154 lines
3.5 KiB
C++

/* Copyright (C) 2014, 2020, MariaDB
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
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA. */
#include "mariadb.h"
#include <sql_class.h>
#include <mysql/service_wsrep.h>
my_bool wsrep_thd_is_BF(const THD *, my_bool)
{ return 0; }
int wsrep_is_wsrep_xid(const void* xid)
{ return 0; }
long long wsrep_xid_seqno(const XID* x)
{ return -1; }
const unsigned char* wsrep_xid_uuid(const XID*)
{
static const unsigned char uuid[16]= {0};
return uuid;
}
bool wsrep_prepare_key_for_innodb(THD* thd, const uchar*, size_t, const uchar*, size_t, struct wsrep_buf*, size_t*)
{ return 1; }
bool wsrep_prepare_key(const uchar*, size_t, const uchar*, size_t, struct wsrep_buf*, size_t*)
{ return 0; }
struct wsrep *get_wsrep()
{ return 0; }
my_bool get_wsrep_recovery()
{ return 0; }
bool wsrep_consistency_check(THD *)
{ return 0; }
void wsrep_lock_rollback()
{ }
my_bool wsrep_on(const THD *)
{ return 0; }
void wsrep_thd_LOCK(const THD *)
{ }
void wsrep_thd_UNLOCK(const THD *)
{ }
const char *wsrep_thd_conflict_state_str(THD *)
{ return 0; }
const char *wsrep_thd_exec_mode_str(THD *)
{ return NULL; }
const char *wsrep_thd_query(const THD *)
{ return "NULL"; }
const char *wsrep_thd_query_state_str(THD *)
{ return 0; }
int wsrep_thd_retry_counter(const THD *)
{ return 0; }
bool wsrep_thd_ignore_table(THD *)
{ return 0; }
long long wsrep_thd_trx_seqno(const THD *)
{ return -1; }
my_bool wsrep_thd_is_aborting(const THD *)
{ return 0; }
void wsrep_set_data_home_dir(const char *)
{ }
my_bool wsrep_thd_is_local(const THD *)
{ return 0; }
void wsrep_thd_self_abort(THD *)
{ }
int wsrep_thd_append_key(THD *, const struct wsrep_key*, int, enum Wsrep_service_key_type)
{ return 0; }
const char* wsrep_thd_client_state_str(const THD*)
{ return 0; }
const char* wsrep_thd_client_mode_str(const THD*)
{ return 0; }
void wsrep_thd_auto_increment_variables(THD *thd,
unsigned long long *offset,
unsigned long long *increment)
{
*offset= thd->variables.auto_increment_offset;
*increment= thd->variables.auto_increment_increment;
}
const char* wsrep_thd_transaction_state_str(const THD*)
{ return 0; }
query_id_t wsrep_thd_transaction_id(const THD *)
{ return 0; }
my_bool wsrep_thd_bf_abort(THD *, THD *, my_bool)
{ return 0; }
my_bool wsrep_thd_order_before(const THD*, const THD *)
{ return 0; }
void wsrep_handle_SR_rollback(THD*, THD*)
{ }
my_bool wsrep_thd_skip_locking(const THD*)
{ return 0;}
const char* wsrep_get_sr_table_name()
{ return 0; }
my_bool wsrep_get_debug()
{ return 0;}
void wsrep_commit_ordered(THD* )
{ }
void wsrep_log(void (*)(const char *, ...), const char *, ...)
{
}
my_bool wsrep_thd_is_applying(const THD*)
{ return 0;}
my_bool wsrep_thd_has_ignored_error(const THD*)
{ return 0;}
void wsrep_thd_set_ignored_error(THD*, my_bool)
{ }
ulong wsrep_OSU_method_get(const THD*)
{ return 0;}
bool wsrep_thd_set_wsrep_aborter(THD*, THD*)
{ return 0;}