~drizzle-trunk/drizzle/development

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
/* Copyright (C) 2000-2006 MySQL AB

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/**
  @file

  Locking functions for mysql.

  Because of the new concurrent inserts, we must first get external locks
  before getting internal locks.  If we do it in the other order, the status
  information is not up to date when called from the lock handler.

  GENERAL DESCRIPTION OF LOCKING

  When not using LOCK TABLES:

  - For each SQL statement mysql_lock_tables() is called for all involved
    tables.
    - mysql_lock_tables() will call
      table_handler->external_lock(thd,locktype) for each table.
      This is followed by a call to thr_multi_lock() for all tables.

  - When statement is done, we call mysql_unlock_tables().
    This will call thr_multi_unlock() followed by
    table_handler->external_lock(thd, F_UNLCK) for each table.

  - Note that mysql_unlock_tables() may be called several times as
    MySQL in some cases can free some tables earlier than others.

  - The above is true both for normal and temporary tables.

  - Temporary non transactional tables are never passed to thr_multi_lock()
    and we never call external_lock(thd, F_UNLOCK) on these.

  When using LOCK TABLES:

  - LOCK TABLE will call mysql_lock_tables() for all tables.
    mysql_lock_tables() will call
    table_handler->external_lock(thd,locktype) for each table.
    This is followed by a call to thr_multi_lock() for all tables.

  - For each statement, we will call table_handler->start_stmt(THD)
    to inform the table handler that we are using the table.

    The tables used can only be tables used in LOCK TABLES or a
    temporary table.

  - When statement is done, we will call ha_commit_stmt(thd);

  - When calling UNLOCK TABLES we call mysql_unlock_tables() for all
    tables used in LOCK TABLES

  If table_handler->external_lock(thd, locktype) fails, we call
  table_handler->external_lock(thd, F_UNLCK) for each table that was locked,
  excluding one that caused failure. That means handler must cleanup itself
  in case external_lock() fails.

  @todo
  Change to use my_malloc() ONLY when using LOCK TABLES command or when
  we are forced to use mysql_lock_merge.
*/

#include "mysql_priv.h"
#include <hash.h>
#include <assert.h>

/**
  @defgroup Locking Locking
  @{
*/

extern HASH open_cache;

/* flags for get_lock_data */
#define GET_LOCK_UNLOCK         1
#define GET_LOCK_STORE_LOCKS    2

static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table,uint count,
				 uint flags, TABLE **write_locked);
static int lock_external(THD *thd, TABLE **table,uint count);
static int unlock_external(THD *thd, TABLE **table,uint count);
static void print_lock_error(int error, const char *);

/*
  Lock tables.

  SYNOPSIS
    mysql_lock_tables()
    thd                         The current thread.
    tables                      An array of pointers to the tables to lock.
    count                       The number of tables to lock.
    flags                       Options:
      MYSQL_LOCK_IGNORE_GLOBAL_READ_LOCK      Ignore a global read lock
      MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY      Ignore SET GLOBAL READ_ONLY
      MYSQL_LOCK_IGNORE_FLUSH                 Ignore a flush tables.
      MYSQL_LOCK_NOTIFY_IF_NEED_REOPEN        Instead of reopening altered
                                              or dropped tables by itself,
                                              mysql_lock_tables() should
                                              notify upper level and rely
                                              on caller doing this.
    need_reopen                 Out parameter, TRUE if some tables were altered
                                or deleted and should be reopened by caller.

  RETURN
    A lock structure pointer on success.
    NULL on error or if some tables should be reopen.
*/

/* Map the return value of thr_lock to an error from errmsg.txt */
static int thr_lock_errno_to_mysql[]=
{ 0, 1, ER_LOCK_WAIT_TIMEOUT, ER_LOCK_DEADLOCK };

/**
  Perform semantic checks for mysql_lock_tables.
  @param thd The current thread
  @param tables The tables to lock
  @param count The number of tables to lock
  @param flags Lock flags
  @return 0 if all the check passed, non zero if a check failed.
*/
int mysql_lock_tables_check(THD *thd, TABLE **tables, uint count, uint flags)
{
  uint system_count;
  uint i;

  DBUG_ENTER("mysql_lock_tables_check");

  system_count= 0;

  for (i=0 ; i<count; i++)
  {
    TABLE *t= tables[i];

    /* Protect against 'fake' partially initialized TABLE_SHARE */
    DBUG_ASSERT(t->s->table_category != TABLE_UNKNOWN_CATEGORY);

    if ((t->s->table_category == TABLE_CATEGORY_SYSTEM) &&
        (t->reginfo.lock_type >= TL_WRITE_ALLOW_WRITE))
    {
      system_count++;
    }
  }

  /*
    Locking of system tables is restricted:
    locking a mix of system and non-system tables in the same lock
    is prohibited, to prevent contention.
  */
  if ((system_count > 0) && (system_count < count))
  {
    my_error(ER_WRONG_LOCK_OF_SYSTEM_TABLE, MYF(0));
    DBUG_RETURN(1);
  }

  DBUG_RETURN(0);
}


/**
  Reset lock type in lock data and free.

  @param mysql_lock Lock structures to reset.

  @note After a locking error we want to quit the locking of the table(s).
        The test case in the bug report for Bug #18544 has the following
        cases: 1. Locking error in lock_external() due to InnoDB timeout.
        2. Locking error in get_lock_data() due to missing write permission.
        3. Locking error in wait_if_global_read_lock() due to lock conflict.

  @note In all these cases we have already set the lock type into the lock
        data of the open table(s). If the table(s) are in the open table
        cache, they could be reused with the non-zero lock type set. This
        could lead to ignoring a different lock type with the next lock.

  @note Clear the lock type of all lock data. This ensures that the next
        lock request will set its lock type properly.
*/

static void reset_lock_data_and_free(MYSQL_LOCK **mysql_lock)
{
  MYSQL_LOCK *sql_lock= *mysql_lock;
  THR_LOCK_DATA **ldata, **ldata_end;

  /* Clear the lock type of all lock data to avoid reusage. */
  for (ldata= sql_lock->locks, ldata_end= ldata + sql_lock->lock_count;
       ldata < ldata_end;
       ldata++)
  {
    /* Reset lock type. */
    (*ldata)->type= TL_UNLOCK;
  }
  my_free((uchar*) sql_lock, MYF(0));
  *mysql_lock= 0;
}


MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count,
                              uint flags, bool *need_reopen)
{
  MYSQL_LOCK *sql_lock;
  TABLE *write_lock_used;
  int rc;

  DBUG_ENTER("mysql_lock_tables");

  *need_reopen= FALSE;

  if (mysql_lock_tables_check(thd, tables, count, flags))
    DBUG_RETURN (NULL);

  for (;;)
  {
    if (! (sql_lock= get_lock_data(thd, tables, count, GET_LOCK_STORE_LOCKS,
                                   &write_lock_used)))
      break;

    if (global_read_lock && write_lock_used &&
        ! (flags & MYSQL_LOCK_IGNORE_GLOBAL_READ_LOCK))
    {
      /*
	Someone has issued LOCK ALL TABLES FOR READ and we want a write lock
	Wait until the lock is gone
      */
      if (wait_if_global_read_lock(thd, 1, 1))
      {
        /* Clear the lock type of all lock data to avoid reusage. */
        reset_lock_data_and_free(&sql_lock);
	break;
      }
      if (thd->version != refresh_version)
      {
        /* Clear the lock type of all lock data to avoid reusage. */
        reset_lock_data_and_free(&sql_lock);
	goto retry;
      }
    }

    if (!(flags & MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY) &&
        write_lock_used &&
        opt_readonly &&
        !thd->slave_thread)
    {
      /*
	Someone has issued SET GLOBAL READ_ONLY=1 and we want a write lock.
        We do not wait for READ_ONLY=0, and fail.
      */
      reset_lock_data_and_free(&sql_lock);
      my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--read-only");
      break;
    }

    thd_proc_info(thd, "System lock");
    DBUG_PRINT("info", ("thd->proc_info %s", thd->proc_info));
    if (sql_lock->table_count && lock_external(thd, sql_lock->table,
                                               sql_lock->table_count))
    {
      /* Clear the lock type of all lock data to avoid reusage. */
      reset_lock_data_and_free(&sql_lock);
      break;
    }
    thd_proc_info(thd, "Table lock");
    DBUG_PRINT("info", ("thd->proc_info %s", thd->proc_info));
    /* Copy the lock data array. thr_multi_lock() reorders its contens. */
    memcpy(sql_lock->locks + sql_lock->lock_count, sql_lock->locks,
           sql_lock->lock_count * sizeof(*sql_lock->locks));
    /* Lock on the copied half of the lock data array. */
    rc= thr_lock_errno_to_mysql[(int) thr_multi_lock(sql_lock->locks +
                                                     sql_lock->lock_count,
                                                     sql_lock->lock_count,
                                                     thd->lock_id)];
    if (rc > 1)                                 /* a timeout or a deadlock */
    {
      if (sql_lock->table_count)
        VOID(unlock_external(thd, sql_lock->table, sql_lock->table_count));
      reset_lock_data_and_free(&sql_lock);
      my_error(rc, MYF(0));
      break;
    }
    else if (rc == 1)                           /* aborted */
    {
      thd->some_tables_deleted=1;		// Try again
      sql_lock->lock_count= 0;                  // Locks are already freed
      // Fall through: unlock, reset lock data, free and retry
    }
    else if (!thd->some_tables_deleted || (flags & MYSQL_LOCK_IGNORE_FLUSH))
    {
      /*
        Thread was killed or lock aborted. Let upper level close all
        used tables and retry or give error.
      */
      break;
    }
    else if (!thd->open_tables)
    {
      // Only using temporary tables, no need to unlock
      thd->some_tables_deleted=0;
      break;
    }
    thd_proc_info(thd, 0);

    /* going to retry, unlock all tables */
    if (sql_lock->lock_count)
        thr_multi_unlock(sql_lock->locks, sql_lock->lock_count);

    if (sql_lock->table_count)
      VOID(unlock_external(thd, sql_lock->table, sql_lock->table_count));

    /*
      If thr_multi_lock fails it resets lock type for tables, which
      were locked before (and including) one that caused error. Lock
      type for other tables preserved.
    */
    reset_lock_data_and_free(&sql_lock);
retry:
    if (flags & MYSQL_LOCK_NOTIFY_IF_NEED_REOPEN)
    {
      *need_reopen= TRUE;
      break;
    }
    if (wait_for_tables(thd))
      break;					// Couldn't open tables
  }
  thd_proc_info(thd, 0);
  if (thd->killed)
  {
    thd->send_kill_message();
    if (sql_lock)
    {
      mysql_unlock_tables(thd,sql_lock);
      sql_lock=0;
    }
  }

  thd->set_time_after_lock();
  DBUG_RETURN (sql_lock);
}


static int lock_external(THD *thd, TABLE **tables, uint count)
{
  register uint i;
  int lock_type,error;
  DBUG_ENTER("lock_external");

  DBUG_PRINT("info", ("count %d", count));
  for (i=1 ; i <= count ; i++, tables++)
  {
    DBUG_ASSERT((*tables)->reginfo.lock_type >= TL_READ);
    lock_type=F_WRLCK;				/* Lock exclusive */
    if ((*tables)->db_stat & HA_READ_ONLY ||
	((*tables)->reginfo.lock_type >= TL_READ &&
	 (*tables)->reginfo.lock_type <= TL_READ_NO_INSERT))
      lock_type=F_RDLCK;

    if ((error=(*tables)->file->ha_external_lock(thd,lock_type)))
    {
      print_lock_error(error, (*tables)->file->table_type());
      while (--i)
      {
        tables--;
	(*tables)->file->ha_external_lock(thd, F_UNLCK);
	(*tables)->current_lock=F_UNLCK;
      }
      DBUG_RETURN(error);
    }
    else
    {
      (*tables)->db_stat &= ~ HA_BLOCK_LOCK;
      (*tables)->current_lock= lock_type;
    }
  }
  DBUG_RETURN(0);
}


void mysql_unlock_tables(THD *thd, MYSQL_LOCK *sql_lock)
{
  DBUG_ENTER("mysql_unlock_tables");
  if (sql_lock->lock_count)
    thr_multi_unlock(sql_lock->locks,sql_lock->lock_count);
  if (sql_lock->table_count)
    VOID(unlock_external(thd,sql_lock->table,sql_lock->table_count));
  my_free((uchar*) sql_lock,MYF(0));
  DBUG_VOID_RETURN;
}

/**
  Unlock some of the tables locked by mysql_lock_tables.

  This will work even if get_lock_data fails (next unlock will free all)
*/

void mysql_unlock_some_tables(THD *thd, TABLE **table,uint count)
{
  MYSQL_LOCK *sql_lock;
  TABLE *write_lock_used;
  if ((sql_lock= get_lock_data(thd, table, count, GET_LOCK_UNLOCK,
                               &write_lock_used)))
    mysql_unlock_tables(thd, sql_lock);
}


/**
  unlock all tables locked for read.
*/

void mysql_unlock_read_tables(THD *thd, MYSQL_LOCK *sql_lock)
{
  uint i,found;
  DBUG_ENTER("mysql_unlock_read_tables");

  /* Move all write locks first */
  THR_LOCK_DATA **lock=sql_lock->locks;
  for (i=found=0 ; i < sql_lock->lock_count ; i++)
  {
    if (sql_lock->locks[i]->type >= TL_WRITE_ALLOW_READ)
    {
      swap_variables(THR_LOCK_DATA *, *lock, sql_lock->locks[i]);
      lock++;
      found++;
    }
  }
  /* unlock the read locked tables */
  if (i != found)
  {
    thr_multi_unlock(lock,i-found);
    sql_lock->lock_count= found;
  }

  /* Then do the same for the external locks */
  /* Move all write locked tables first */
  TABLE **table=sql_lock->table;
  for (i=found=0 ; i < sql_lock->table_count ; i++)
  {
    DBUG_ASSERT(sql_lock->table[i]->lock_position == i);
    if ((uint) sql_lock->table[i]->reginfo.lock_type >= TL_WRITE_ALLOW_READ)
    {
      swap_variables(TABLE *, *table, sql_lock->table[i]);
      table++;
      found++;
    }
  }
  /* Unlock all read locked tables */
  if (i != found)
  {
    VOID(unlock_external(thd,table,i-found));
    sql_lock->table_count=found;
  }
  /* Fix the lock positions in TABLE */
  table= sql_lock->table;
  found= 0;
  for (i= 0; i < sql_lock->table_count; i++)
  {
    TABLE *tbl= *table;
    tbl->lock_position= table - sql_lock->table;
    tbl->lock_data_start= found;
    found+= tbl->lock_count;
    table++;
  }
  DBUG_VOID_RETURN;
}


/**
  Try to find the table in the list of locked tables.
  In case of success, unlock the table and remove it from this list.

  @note This function has a legacy side effect: the table is
  unlocked even if it is not found in the locked list.
  It's not clear if this side effect is intentional or still
  desirable. It might lead to unmatched calls to
  unlock_external(). Moreover, a discrepancy can be left
  unnoticed by the storage engine, because in
  unlock_external() we call handler::external_lock(F_UNLCK) only
  if table->current_lock is not F_UNLCK.

  @param  thd             thread context
  @param  locked          list of locked tables
  @param  table           the table to unlock
  @param  always_unlock   specify explicitly if the legacy side
                          effect is desired.
*/

void mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table,
                       bool always_unlock)
{
  if (always_unlock == TRUE)
    mysql_unlock_some_tables(thd, &table, /* table count */ 1);
  if (locked)
  {
    register uint i;
    for (i=0; i < locked->table_count; i++)
    {
      if (locked->table[i] == table)
      {
        uint  j, removed_locks, old_tables;
        TABLE *tbl;
        uint lock_data_end;

        DBUG_ASSERT(table->lock_position == i);

        /* Unlock if not yet unlocked */
        if (always_unlock == FALSE)
          mysql_unlock_some_tables(thd, &table, /* table count */ 1);

        /* Decrement table_count in advance, making below expressions easier */
        old_tables= --locked->table_count;

        /* The table has 'removed_locks' lock data elements in locked->locks */
        removed_locks= table->lock_count;

        /* Move down all table pointers above 'i'. */
	bmove((char*) (locked->table+i),
	      (char*) (locked->table+i+1),
	      (old_tables - i) * sizeof(TABLE*));

        lock_data_end= table->lock_data_start + table->lock_count;
        /* Move down all lock data pointers above 'table->lock_data_end-1' */
        bmove((char*) (locked->locks + table->lock_data_start),
              (char*) (locked->locks + lock_data_end),
              (locked->lock_count - lock_data_end) *
              sizeof(THR_LOCK_DATA*));

        /*
          Fix moved table elements.
          lock_position is the index in the 'locked->table' array,
          it must be fixed by one.
          table->lock_data_start is pointer to the lock data for this table
          in the 'locked->locks' array, they must be fixed by 'removed_locks',
          the lock data count of the removed table.
        */
        for (j= i ; j < old_tables; j++)
        {
          tbl= locked->table[j];
          tbl->lock_position--;
          DBUG_ASSERT(tbl->lock_position == j);
          tbl->lock_data_start-= removed_locks;
        }

        /* Finally adjust lock_count. */
        locked->lock_count-= removed_locks;
	break;
      }
    }
  }
}

/* Downgrade all locks on a table to new WRITE level from WRITE_ONLY */

void mysql_lock_downgrade_write(THD *thd, TABLE *table,
                                thr_lock_type new_lock_type)
{
  MYSQL_LOCK *locked;
  TABLE *write_lock_used;
  if ((locked = get_lock_data(thd, &table, 1, GET_LOCK_UNLOCK,
                              &write_lock_used)))
  {
    for (uint i=0; i < locked->lock_count; i++)
      thr_downgrade_write_lock(locked->locks[i], new_lock_type);
    my_free((uchar*) locked,MYF(0));
  }
}


/** Abort all other threads waiting to get lock in table. */

void mysql_lock_abort(THD *thd, TABLE *table, bool upgrade_lock)
{
  MYSQL_LOCK *locked;
  TABLE *write_lock_used;
  DBUG_ENTER("mysql_lock_abort");

  if ((locked= get_lock_data(thd, &table, 1, GET_LOCK_UNLOCK,
                             &write_lock_used)))
  {
    for (uint i=0; i < locked->lock_count; i++)
      thr_abort_locks(locked->locks[i]->lock, upgrade_lock);
    my_free((uchar*) locked,MYF(0));
  }
  DBUG_VOID_RETURN;
}


/**
  Abort one thread / table combination.

  @param thd	   Thread handler
  @param table	   Table that should be removed from lock queue

  @retval
    0  Table was not locked by another thread
  @retval
    1  Table was locked by at least one other thread
*/

bool mysql_lock_abort_for_thread(THD *thd, TABLE *table)
{
  MYSQL_LOCK *locked;
  TABLE *write_lock_used;
  bool result= FALSE;
  DBUG_ENTER("mysql_lock_abort_for_thread");

  if ((locked= get_lock_data(thd, &table, 1, GET_LOCK_UNLOCK,
                             &write_lock_used)))
  {
    for (uint i=0; i < locked->lock_count; i++)
    {
      if (thr_abort_locks_for_thread(locked->locks[i]->lock,
                                     table->in_use->thread_id))
        result= TRUE;
    }
    my_free((uchar*) locked,MYF(0));
  }
  DBUG_RETURN(result);
}


MYSQL_LOCK *mysql_lock_merge(MYSQL_LOCK *a,MYSQL_LOCK *b)
{
  MYSQL_LOCK *sql_lock;
  TABLE **table, **end_table;
  DBUG_ENTER("mysql_lock_merge");

  if (!(sql_lock= (MYSQL_LOCK*)
	my_malloc(sizeof(*sql_lock)+
		  sizeof(THR_LOCK_DATA*)*(a->lock_count+b->lock_count)+
		  sizeof(TABLE*)*(a->table_count+b->table_count),MYF(MY_WME))))
    DBUG_RETURN(0);				// Fatal error
  sql_lock->lock_count=a->lock_count+b->lock_count;
  sql_lock->table_count=a->table_count+b->table_count;
  sql_lock->locks=(THR_LOCK_DATA**) (sql_lock+1);
  sql_lock->table=(TABLE**) (sql_lock->locks+sql_lock->lock_count);
  memcpy(sql_lock->locks,a->locks,a->lock_count*sizeof(*a->locks));
  memcpy(sql_lock->locks+a->lock_count,b->locks,
	 b->lock_count*sizeof(*b->locks));
  memcpy(sql_lock->table,a->table,a->table_count*sizeof(*a->table));
  memcpy(sql_lock->table+a->table_count,b->table,
	 b->table_count*sizeof(*b->table));

  /*
    Now adjust lock_position and lock_data_start for all objects that was
    moved in 'b' (as there is now all objects in 'a' before these).
  */
  for (table= sql_lock->table + a->table_count,
         end_table= table + b->table_count;
       table < end_table;
       table++)
  {
    (*table)->lock_position+=   a->table_count;
    (*table)->lock_data_start+= a->lock_count;
  }

  /* Delete old, not needed locks */
  my_free((uchar*) a,MYF(0));
  my_free((uchar*) b,MYF(0));
  DBUG_RETURN(sql_lock);
}


/**
  Find duplicate lock in tables.

  Temporary tables are ignored here like they are ignored in
  get_lock_data(). If we allow two opens on temporary tables later,
  both functions should be checked.

  @param thd                 The current thread.
  @param needle              The table to check for duplicate lock.
  @param haystack            The list of tables to search for the dup lock.

  @note
    This is mainly meant for MERGE tables in INSERT ... SELECT
    situations. The 'real', underlying tables can be found only after
    the MERGE tables are opened. This function assumes that the tables are
    already locked.

  @retval
    NULL    No duplicate lock found.
  @retval
    !NULL   First table from 'haystack' that matches a lock on 'needle'.
*/

TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
                                      TABLE_LIST *haystack)
{
  MYSQL_LOCK            *mylock;
  TABLE                 **lock_tables;
  TABLE                 *table;
  TABLE                 *table2;
  THR_LOCK_DATA         **lock_locks;
  THR_LOCK_DATA         **table_lock_data;
  THR_LOCK_DATA         **end_data;
  THR_LOCK_DATA         **lock_data2;
  THR_LOCK_DATA         **end_data2;
  DBUG_ENTER("mysql_lock_have_duplicate");

  /*
    Table may not be defined for derived or view tables.
    Table may not be part of a lock for delayed operations.
  */
  if (! (table= needle->table) || ! table->lock_count)
    goto end;

  /* A temporary table does not have locks. */
  if (table->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE)
    goto end;

  /* Get command lock or LOCK TABLES lock. Maybe empty for INSERT DELAYED. */
  if (! (mylock= thd->lock ? thd->lock : thd->locked_tables))
    goto end;

  /* If we have less than two tables, we cannot have duplicates. */
  if (mylock->table_count < 2)
    goto end;

  lock_locks=  mylock->locks;
  lock_tables= mylock->table;

  /* Prepare table related variables that don't change in loop. */
  DBUG_ASSERT((table->lock_position < mylock->table_count) &&
              (table == lock_tables[table->lock_position]));
  table_lock_data= lock_locks + table->lock_data_start;
  end_data= table_lock_data + table->lock_count;

  for (; haystack; haystack= haystack->next_global)
  {
    if (haystack->placeholder())
      continue;
    table2= haystack->table;
    if (table2->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE)
      continue;

    /* All tables in list must be in lock. */
    DBUG_ASSERT((table2->lock_position < mylock->table_count) &&
                (table2 == lock_tables[table2->lock_position]));

    for (lock_data2=  lock_locks + table2->lock_data_start,
           end_data2= lock_data2 + table2->lock_count;
         lock_data2 < end_data2;
         lock_data2++)
    {
      THR_LOCK_DATA **lock_data;
      THR_LOCK *lock2= (*lock_data2)->lock;

      for (lock_data= table_lock_data;
           lock_data < end_data;
           lock_data++)
      {
        if ((*lock_data)->lock == lock2)
        {
          DBUG_PRINT("info", ("haystack match: '%s'", haystack->table_name));
          DBUG_RETURN(haystack);
        }
      }
    }
  }

 end:
  DBUG_PRINT("info", ("no duplicate found"));
  DBUG_RETURN(NULL);
}


/** Unlock a set of external. */

static int unlock_external(THD *thd, TABLE **table,uint count)
{
  int error,error_code;
  DBUG_ENTER("unlock_external");

  error_code=0;
  do
  {
    if ((*table)->current_lock != F_UNLCK)
    {
      (*table)->current_lock = F_UNLCK;
      if ((error=(*table)->file->ha_external_lock(thd, F_UNLCK)))
      {
	error_code=error;
	print_lock_error(error_code, (*table)->file->table_type());
      }
    }
    table++;
  } while (--count);
  DBUG_RETURN(error_code);
}


/**
  Get lock structures from table structs and initialize locks.

  @param thd		    Thread handler
  @param table_ptr	    Pointer to tables that should be locks
  @param flags		    One of:
           - GET_LOCK_UNLOCK      : If we should send TL_IGNORE to store lock
           - GET_LOCK_STORE_LOCKS : Store lock info in TABLE
  @param write_lock_used   Store pointer to last table with WRITE_ALLOW_WRITE
*/

static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count,
				 uint flags, TABLE **write_lock_used)
{
  uint i,tables,lock_count;
  MYSQL_LOCK *sql_lock;
  THR_LOCK_DATA **locks, **locks_buf, **locks_start;
  TABLE **to, **table_buf;
  DBUG_ENTER("get_lock_data");

  DBUG_ASSERT((flags == GET_LOCK_UNLOCK) || (flags == GET_LOCK_STORE_LOCKS));

  DBUG_PRINT("info", ("count %d", count));
  *write_lock_used=0;
  for (i=tables=lock_count=0 ; i < count ; i++)
  {
    TABLE *t= table_ptr[i];

    if (t->s->tmp_table != NON_TRANSACTIONAL_TMP_TABLE)
    {
      tables+= t->file->lock_count();
      lock_count++;
    }
  }

  /*
    Allocating twice the number of pointers for lock data for use in
    thr_mulit_lock(). This function reorders the lock data, but cannot
    update the table values. So the second part of the array is copied
    from the first part immediately before calling thr_multi_lock().
  */
  if (!(sql_lock= (MYSQL_LOCK*)
	my_malloc(sizeof(*sql_lock) +
		  sizeof(THR_LOCK_DATA*) * tables * 2 +
                  sizeof(table_ptr) * lock_count,
		  MYF(0))))
    DBUG_RETURN(0);
  locks= locks_buf= sql_lock->locks= (THR_LOCK_DATA**) (sql_lock + 1);
  to= table_buf= sql_lock->table= (TABLE**) (locks + tables * 2);
  sql_lock->table_count=lock_count;

  for (i=0 ; i < count ; i++)
  {
    TABLE *table;
    enum thr_lock_type lock_type;

    if ((table=table_ptr[i])->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE)
      continue;
    lock_type= table->reginfo.lock_type;
    DBUG_ASSERT (lock_type != TL_WRITE_DEFAULT);
    if (lock_type >= TL_WRITE_ALLOW_WRITE)
    {
      *write_lock_used=table;
      if (table->db_stat & HA_READ_ONLY)
      {
	my_error(ER_OPEN_AS_READONLY,MYF(0),table->alias);
        /* Clear the lock type of the lock data that are stored already. */
        sql_lock->lock_count= locks - sql_lock->locks;
        reset_lock_data_and_free(&sql_lock);
	DBUG_RETURN(0);
      }
    }
    THR_LOCK_DATA **org_locks = locks;
    locks_start= locks;
    locks= table->file->store_lock(thd, locks,
                                   (flags & GET_LOCK_UNLOCK) ? TL_IGNORE :
                                   lock_type);
    if (flags & GET_LOCK_STORE_LOCKS)
    {
      table->lock_position=   (uint) (to - table_buf);
      table->lock_data_start= (uint) (locks_start - locks_buf);
      table->lock_count=      (uint) (locks - locks_start);
    }
    *to++= table;
    if (locks)
      for ( ; org_locks != locks ; org_locks++)
	(*org_locks)->debug_print_param= (void *) table;
  }
  /*
    We do not use 'tables', because there are cases where store_lock()
    returns less locks than lock_count() claimed. This can happen when
    a FLUSH TABLES tries to abort locks from a MERGE table of another
    thread. When that thread has just opened the table, but not yet
    attached its children, it cannot return the locks. lock_count()
    always returns the number of locks that an attached table has.
    This is done to avoid the reverse situation: If lock_count() would
    return 0 for a non-attached MERGE table, and that table becomes
    attached between the calls to lock_count() and store_lock(), then
    we would have allocated too little memory for the lock data. Now
    we may allocate too much, but better safe than memory overrun.
    And in the FLUSH case, the memory is released quickly anyway.
  */
  sql_lock->lock_count= locks - locks_buf;
  DBUG_PRINT("info", ("sql_lock->table_count %d sql_lock->lock_count %d",
                      sql_lock->table_count, sql_lock->lock_count));
  DBUG_RETURN(sql_lock);
}


/*****************************************************************************
  Lock table based on the name.
  This is used when we need total access to a closed, not open table
*****************************************************************************/

/**
  Lock and wait for the named lock.

  @param thd			Thread handler
  @param table_list		Lock first table in this list


  @note
    Works together with global read lock.

  @retval
    0	ok
  @retval
    1	error
*/

int lock_and_wait_for_table_name(THD *thd, TABLE_LIST *table_list)
{
  int lock_retcode;
  int error= -1;
  DBUG_ENTER("lock_and_wait_for_table_name");

  if (wait_if_global_read_lock(thd, 0, 1))
    DBUG_RETURN(1);
  VOID(pthread_mutex_lock(&LOCK_open));
  if ((lock_retcode = lock_table_name(thd, table_list, TRUE)) < 0)
    goto end;
  if (lock_retcode && wait_for_locked_table_names(thd, table_list))
  {
    unlock_table_name(thd, table_list);
    goto end;
  }
  error=0;

end:
  pthread_mutex_unlock(&LOCK_open);
  start_waiting_global_read_lock(thd);
  DBUG_RETURN(error);
}


/**
  Put a not open table with an old refresh version in the table cache.

  @param thd			Thread handler
  @param table_list		Lock first table in this list
  @param check_in_use           Do we need to check if table already in use by us

  @note
    One must have a lock on LOCK_open!

  @warning
    If you are going to update the table, you should use
    lock_and_wait_for_table_name instead of this function as this works
    together with 'FLUSH TABLES WITH READ LOCK'

  @note
    This will force any other threads that uses the table to release it
    as soon as possible.

  @return
    < 0 error
  @return
    == 0 table locked
  @return
    > 0  table locked, but someone is using it
*/

int lock_table_name(THD *thd, TABLE_LIST *table_list, bool check_in_use)
{
  TABLE *table;
  char  key[MAX_DBKEY_LENGTH];
  char *db= table_list->db;
  uint  key_length;
  bool  found_locked_table= FALSE;
  HASH_SEARCH_STATE state;
  DBUG_ENTER("lock_table_name");
  DBUG_PRINT("enter",("db: %s  name: %s", db, table_list->table_name));

  key_length= create_table_def_key(thd, key, table_list, 0);

  if (check_in_use)
  {
    /* Only insert the table if we haven't insert it already */
    for (table=(TABLE*) hash_first(&open_cache, (uchar*)key,
                                   key_length, &state);
         table ;
         table = (TABLE*) hash_next(&open_cache,(uchar*) key,
                                    key_length, &state))
    {
      if (table->reginfo.lock_type < TL_WRITE)
      {
        if (table->in_use == thd)
          found_locked_table= TRUE;
        continue;
      }

      if (table->in_use == thd)
      {
        DBUG_PRINT("info", ("Table is in use"));
        table->s->version= 0;                  // Ensure no one can use this
        table->locked_by_name= 1;
        DBUG_RETURN(0);
      }
    }
  }

  if (thd->locked_tables && thd->locked_tables->table_count &&
      ! find_temporary_table(thd, table_list->db, table_list->table_name))
  {
    if (found_locked_table)
      my_error(ER_TABLE_NOT_LOCKED_FOR_WRITE, MYF(0), table_list->alias);
    else
      my_error(ER_TABLE_NOT_LOCKED, MYF(0), table_list->alias);

    DBUG_RETURN(-1);
  }

  if (!(table= table_cache_insert_placeholder(thd, key, key_length)))
    DBUG_RETURN(-1);

  table_list->table=table;

  /* Return 1 if table is in use */
  DBUG_RETURN(test(remove_table_from_cache(thd, db, table_list->table_name,
             check_in_use ? RTFC_NO_FLAG : RTFC_WAIT_OTHER_THREAD_FLAG)));
}


void unlock_table_name(THD *thd, TABLE_LIST *table_list)
{
  if (table_list->table)
  {
    hash_delete(&open_cache, (uchar*) table_list->table);
    broadcast_refresh();
  }
}


static bool locked_named_table(THD *thd, TABLE_LIST *table_list)
{
  for (; table_list ; table_list=table_list->next_local)
  {
    TABLE *table= table_list->table;
    if (table)
    {
      TABLE *save_next= table->next;
      bool result;
      table->next= 0;
      result= table_is_used(table_list->table, 0);
      table->next= save_next;
      if (result)
        return 1;
    }
  }
  return 0;					// All tables are locked
}


bool wait_for_locked_table_names(THD *thd, TABLE_LIST *table_list)
{
  bool result=0;
  DBUG_ENTER("wait_for_locked_table_names");

  safe_mutex_assert_owner(&LOCK_open);

  while (locked_named_table(thd,table_list))
  {
    if (thd->killed)
    {
      result=1;
      break;
    }
    wait_for_condition(thd, &LOCK_open, &COND_refresh);
    pthread_mutex_lock(&LOCK_open);
  }
  DBUG_RETURN(result);
}


/**
  Lock all tables in list with a name lock.

  REQUIREMENTS
  - One must have a lock on LOCK_open when calling this

  @param thd			Thread handle
  @param table_list		Names of tables to lock

  @note
    If you are just locking one table, you should use
    lock_and_wait_for_table_name().

  @retval
    0	ok
  @retval
    1	Fatal error (end of memory ?)
*/

bool lock_table_names(THD *thd, TABLE_LIST *table_list)
{
  bool got_all_locks=1;
  TABLE_LIST *lock_table;

  for (lock_table= table_list; lock_table; lock_table= lock_table->next_local)
  {
    int got_lock;
    if ((got_lock=lock_table_name(thd,lock_table, TRUE)) < 0)
      goto end;					// Fatal error
    if (got_lock)
      got_all_locks=0;				// Someone is using table
  }

  /* If some table was in use, wait until we got the lock */
  if (!got_all_locks && wait_for_locked_table_names(thd, table_list))
    goto end;
  return 0;

end:
  unlock_table_names(thd, table_list, lock_table);
  return 1;
}


/**
  Unlock all tables in list with a name lock.

  @param thd        Thread handle.
  @param table_list Names of tables to lock.

  @note 
    This function needs to be protected by LOCK_open. If we're 
    under LOCK TABLES, this function does not work as advertised. Namely,
    it does not exclude other threads from using this table and does not
    put an exclusive name lock on this table into the table cache.

  @see lock_table_names
  @see unlock_table_names

  @retval TRUE An error occured.
  @retval FALSE Name lock successfully acquired.
*/

bool lock_table_names_exclusively(THD *thd, TABLE_LIST *table_list)
{
  if (lock_table_names(thd, table_list))
    return TRUE;

  /*
    Upgrade the table name locks from semi-exclusive to exclusive locks.
  */
  for (TABLE_LIST *table= table_list; table; table= table->next_global)
  {
    if (table->table)
      table->table->open_placeholder= 1;
  }
  return FALSE;
}


/**
  Test is 'table' is protected by an exclusive name lock.

  @param[in] thd        The current thread handler
  @param[in] table_list Table container containing the single table to be
                        tested

  @note Needs to be protected by LOCK_open mutex.

  @return Error status code
    @retval TRUE Table is protected
    @retval FALSE Table is not protected
*/

bool
is_table_name_exclusively_locked_by_this_thread(THD *thd,
                                                TABLE_LIST *table_list)
{
  char  key[MAX_DBKEY_LENGTH];
  uint  key_length;

  key_length= create_table_def_key(thd, key, table_list, 0);

  return is_table_name_exclusively_locked_by_this_thread(thd, (uchar *)key,
                                                         key_length);
}


/**
  Test is 'table key' is protected by an exclusive name lock.

  @param[in] thd        The current thread handler.
  @param[in] key
  @param[in] key_length

  @note Needs to be protected by LOCK_open mutex

  @retval TRUE Table is protected
  @retval FALSE Table is not protected
 */

bool
is_table_name_exclusively_locked_by_this_thread(THD *thd, uchar *key,
                                                int key_length)
{
  HASH_SEARCH_STATE state;
  TABLE *table;

  for (table= (TABLE*) hash_first(&open_cache, key,
                                  key_length, &state);
       table ;
       table= (TABLE*) hash_next(&open_cache, key,
                                 key_length, &state))
  {
    if (table->in_use == thd &&
        table->open_placeholder == 1 &&
        table->s->version == 0)
      return TRUE;
  }

  return FALSE;
}

/**
  Unlock all tables in list with a name lock.

  @param
    thd			Thread handle
  @param
    table_list		Names of tables to unlock
  @param
    last_table		Don't unlock any tables after this one.
			        (default 0, which will unlock all tables)

  @note
    One must have a lock on LOCK_open when calling this.

  @note
    This function will broadcast refresh signals to inform other threads
    that the name locks are removed.

  @retval
    0	ok
  @retval
    1	Fatal error (end of memory ?)
*/

void unlock_table_names(THD *thd, TABLE_LIST *table_list,
			TABLE_LIST *last_table)
{
  DBUG_ENTER("unlock_table_names");
  for (TABLE_LIST *table= table_list;
       table != last_table;
       table= table->next_local)
    unlock_table_name(thd,table);
  broadcast_refresh();
  DBUG_VOID_RETURN;
}


static void print_lock_error(int error, const char *table)
{
  int textno;
  DBUG_ENTER("print_lock_error");

  switch (error) {
  case HA_ERR_LOCK_WAIT_TIMEOUT:
    textno=ER_LOCK_WAIT_TIMEOUT;
    break;
  case HA_ERR_READ_ONLY_TRANSACTION:
    textno=ER_READ_ONLY_TRANSACTION;
    break;
  case HA_ERR_LOCK_DEADLOCK:
    textno=ER_LOCK_DEADLOCK;
    break;
  case HA_ERR_WRONG_COMMAND:
    textno=ER_ILLEGAL_HA;
    break;
  default:
    textno=ER_CANT_LOCK;
    break;
  }

  if ( textno == ER_ILLEGAL_HA )
    my_error(textno, MYF(ME_BELL+ME_OLDWIN+ME_WAITTANG), table);
  else
    my_error(textno, MYF(ME_BELL+ME_OLDWIN+ME_WAITTANG), error);

  DBUG_VOID_RETURN;
}


/****************************************************************************
  Handling of global read locks

  Taking the global read lock is TWO steps (2nd step is optional; without
  it, COMMIT of existing transactions will be allowed):
  lock_global_read_lock() THEN make_global_read_lock_block_commit().

  The global locks are handled through the global variables:
  global_read_lock
    count of threads which have the global read lock (i.e. have completed at
    least the first step above)
  global_read_lock_blocks_commit
    count of threads which have the global read lock and block
    commits (i.e. are in or have completed the second step above)
  waiting_for_read_lock
    count of threads which want to take a global read lock but cannot
  protect_against_global_read_lock
    count of threads which have set protection against global read lock.

  access to them is protected with a mutex LOCK_global_read_lock

  (XXX: one should never take LOCK_open if LOCK_global_read_lock is
  taken, otherwise a deadlock may occur. Other mutexes could be a
  problem too - grep the code for global_read_lock if you want to use
  any other mutex here) Also one must not hold LOCK_open when calling
  wait_if_global_read_lock(). When the thread with the global read lock
  tries to close its tables, it needs to take LOCK_open in
  close_thread_table().

  How blocking of threads by global read lock is achieved: that's
  advisory. Any piece of code which should be blocked by global read lock must
  be designed like this:
  - call to wait_if_global_read_lock(). When this returns 0, no global read
  lock is owned; if argument abort_on_refresh was 0, none can be obtained.
  - job
  - if abort_on_refresh was 0, call to start_waiting_global_read_lock() to
  allow other threads to get the global read lock. I.e. removal of the
  protection.
  (Note: it's a bit like an implementation of rwlock).

  [ I am sorry to mention some SQL syntaxes below I know I shouldn't but found
  no better descriptive way ]

  Why does FLUSH TABLES WITH READ LOCK need to block COMMIT: because it's used
  to read a non-moving SHOW MASTER STATUS, and a COMMIT writes to the binary
  log.

  Why getting the global read lock is two steps and not one. Because FLUSH
  TABLES WITH READ LOCK needs to insert one other step between the two:
  flushing tables. So the order is
  1) lock_global_read_lock() (prevents any new table write locks, i.e. stalls
  all new updates)
  2) close_cached_tables() (the FLUSH TABLES), which will wait for tables
  currently opened and being updated to close (so it's possible that there is
  a moment where all new updates of server are stalled *and* FLUSH TABLES WITH
  READ LOCK is, too).
  3) make_global_read_lock_block_commit().
  If we have merged 1) and 3) into 1), we would have had this deadlock:
  imagine thread 1 and 2, in non-autocommit mode, thread 3, and an InnoDB
  table t.
  thd1: SELECT * FROM t FOR UPDATE;
  thd2: UPDATE t SET a=1; # blocked by row-level locks of thd1
  thd3: FLUSH TABLES WITH READ LOCK; # blocked in close_cached_tables() by the
  table instance of thd2
  thd1: COMMIT; # blocked by thd3.
  thd1 blocks thd2 which blocks thd3 which blocks thd1: deadlock.

  Note that we need to support that one thread does
  FLUSH TABLES WITH READ LOCK; and then COMMIT;
  (that's what innobackup does, for some good reason).
  So in this exceptional case the COMMIT should not be blocked by the FLUSH
  TABLES WITH READ LOCK.

****************************************************************************/

volatile uint global_read_lock=0;
volatile uint global_read_lock_blocks_commit=0;
static volatile uint protect_against_global_read_lock=0;
static volatile uint waiting_for_read_lock=0;

#define GOT_GLOBAL_READ_LOCK               1
#define MADE_GLOBAL_READ_LOCK_BLOCK_COMMIT 2

bool lock_global_read_lock(THD *thd)
{
  DBUG_ENTER("lock_global_read_lock");

  if (!thd->global_read_lock)
  {
    const char *old_message;
    (void) pthread_mutex_lock(&LOCK_global_read_lock);
    old_message=thd->enter_cond(&COND_global_read_lock, &LOCK_global_read_lock,
                                "Waiting to get readlock");
    DBUG_PRINT("info",
	       ("waiting_for: %d  protect_against: %d",
		waiting_for_read_lock, protect_against_global_read_lock));

    waiting_for_read_lock++;
    while (protect_against_global_read_lock && !thd->killed)
      pthread_cond_wait(&COND_global_read_lock, &LOCK_global_read_lock);
    waiting_for_read_lock--;
    if (thd->killed)
    {
      thd->exit_cond(old_message);
      DBUG_RETURN(1);
    }
    thd->global_read_lock= GOT_GLOBAL_READ_LOCK;
    global_read_lock++;
    thd->exit_cond(old_message); // this unlocks LOCK_global_read_lock
  }
  /*
    We DON'T set global_read_lock_blocks_commit now, it will be set after
    tables are flushed (as the present function serves for FLUSH TABLES WITH
    READ LOCK only). Doing things in this order is necessary to avoid
    deadlocks (we must allow COMMIT until all tables are closed; we should not
    forbid it before, or we can have a 3-thread deadlock if 2 do SELECT FOR
    UPDATE and one does FLUSH TABLES WITH READ LOCK).
  */
  DBUG_RETURN(0);
}


void unlock_global_read_lock(THD *thd)
{
  uint tmp;
  DBUG_ENTER("unlock_global_read_lock");
  DBUG_PRINT("info",
             ("global_read_lock: %u  global_read_lock_blocks_commit: %u",
              global_read_lock, global_read_lock_blocks_commit));

  pthread_mutex_lock(&LOCK_global_read_lock);
  tmp= --global_read_lock;
  if (thd->global_read_lock == MADE_GLOBAL_READ_LOCK_BLOCK_COMMIT)
    --global_read_lock_blocks_commit;
  pthread_mutex_unlock(&LOCK_global_read_lock);
  /* Send the signal outside the mutex to avoid a context switch */
  if (!tmp)
  {
    DBUG_PRINT("signal", ("Broadcasting COND_global_read_lock"));
    pthread_cond_broadcast(&COND_global_read_lock);
  }
  thd->global_read_lock= 0;

  DBUG_VOID_RETURN;
}

#define must_wait (global_read_lock &&                             \
                   (is_not_commit ||                               \
                    global_read_lock_blocks_commit))

bool wait_if_global_read_lock(THD *thd, bool abort_on_refresh,
                              bool is_not_commit)
{
  const char *old_message= NULL;
  bool result= 0, need_exit_cond;
  DBUG_ENTER("wait_if_global_read_lock");

  /*
    Assert that we do not own LOCK_open. If we would own it, other
    threads could not close their tables. This would make a pretty
    deadlock.
  */
  safe_mutex_assert_not_owner(&LOCK_open);

  (void) pthread_mutex_lock(&LOCK_global_read_lock);
  if ((need_exit_cond= must_wait))
  {
    if (thd->global_read_lock)		// This thread had the read locks
    {
      if (is_not_commit)
        my_message(ER_CANT_UPDATE_WITH_READLOCK,
                   ER(ER_CANT_UPDATE_WITH_READLOCK), MYF(0));
      (void) pthread_mutex_unlock(&LOCK_global_read_lock);
      /*
        We allow FLUSHer to COMMIT; we assume FLUSHer knows what it does.
        This allowance is needed to not break existing versions of innobackup
        which do a BEGIN; INSERT; FLUSH TABLES WITH READ LOCK; COMMIT.
      */
      DBUG_RETURN(is_not_commit);
    }
    old_message=thd->enter_cond(&COND_global_read_lock, &LOCK_global_read_lock,
				"Waiting for release of readlock");
    while (must_wait && ! thd->killed &&
	   (!abort_on_refresh || thd->version == refresh_version))
    {
      DBUG_PRINT("signal", ("Waiting for COND_global_read_lock"));
      (void) pthread_cond_wait(&COND_global_read_lock, &LOCK_global_read_lock);
      DBUG_PRINT("signal", ("Got COND_global_read_lock"));
    }
    if (thd->killed)
      result=1;
  }
  if (!abort_on_refresh && !result)
    protect_against_global_read_lock++;
  /*
    The following is only true in case of a global read locks (which is rare)
    and if old_message is set
  */
  if (unlikely(need_exit_cond))
    thd->exit_cond(old_message); // this unlocks LOCK_global_read_lock
  else
    pthread_mutex_unlock(&LOCK_global_read_lock);
  DBUG_RETURN(result);
}


void start_waiting_global_read_lock(THD *thd)
{
  bool tmp;
  DBUG_ENTER("start_waiting_global_read_lock");
  if (unlikely(thd->global_read_lock))
    DBUG_VOID_RETURN;
  (void) pthread_mutex_lock(&LOCK_global_read_lock);
  tmp= (!--protect_against_global_read_lock &&
        (waiting_for_read_lock || global_read_lock_blocks_commit));
  (void) pthread_mutex_unlock(&LOCK_global_read_lock);
  if (tmp)
    pthread_cond_broadcast(&COND_global_read_lock);
  DBUG_VOID_RETURN;
}


bool make_global_read_lock_block_commit(THD *thd)
{
  bool error;
  const char *old_message;
  DBUG_ENTER("make_global_read_lock_block_commit");
  /*
    If we didn't succeed lock_global_read_lock(), or if we already suceeded
    make_global_read_lock_block_commit(), do nothing.
  */
  if (thd->global_read_lock != GOT_GLOBAL_READ_LOCK)
    DBUG_RETURN(0);
  pthread_mutex_lock(&LOCK_global_read_lock);
  /* increment this BEFORE waiting on cond (otherwise race cond) */
  global_read_lock_blocks_commit++;
  /* For testing we set up some blocking, to see if we can be killed */
  DBUG_EXECUTE_IF("make_global_read_lock_block_commit_loop",
                  protect_against_global_read_lock++;);
  old_message= thd->enter_cond(&COND_global_read_lock, &LOCK_global_read_lock,
                               "Waiting for all running commits to finish");
  while (protect_against_global_read_lock && !thd->killed)
    pthread_cond_wait(&COND_global_read_lock, &LOCK_global_read_lock);
  DBUG_EXECUTE_IF("make_global_read_lock_block_commit_loop",
                  protect_against_global_read_lock--;);
  if ((error= test(thd->killed)))
    global_read_lock_blocks_commit--; // undo what we did
  else
    thd->global_read_lock= MADE_GLOBAL_READ_LOCK_BLOCK_COMMIT;
  thd->exit_cond(old_message); // this unlocks LOCK_global_read_lock
  DBUG_RETURN(error);
}


/**
  Broadcast COND_refresh and COND_global_read_lock.

    Due to a bug in a threading library it could happen that a signal
    did not reach its target. A condition for this was that the same
    condition variable was used with different mutexes in
    pthread_cond_wait(). Some time ago we changed LOCK_open to
    LOCK_global_read_lock in global read lock handling. So COND_refresh
    was used with LOCK_open and LOCK_global_read_lock.

    We did now also change from COND_refresh to COND_global_read_lock
    in global read lock handling. But now it is necessary to signal
    both conditions at the same time.

  @note
    When signalling COND_global_read_lock within the global read lock
    handling, it is not necessary to also signal COND_refresh.
*/

void broadcast_refresh(void)
{
  VOID(pthread_cond_broadcast(&COND_refresh));
  VOID(pthread_cond_broadcast(&COND_global_read_lock));
}


/*
  Try to get transactional table locks for the tables in the list.

  SYNOPSIS
    try_transactional_lock()
      thd                       Thread handle
      table_list                List of tables to lock

  DESCRIPTION
    This is called if transactional table locks are requested for all
    tables in table_list and no non-transactional locks pre-exist.

  RETURN
    0                   OK. All tables are transactional locked.
    1                   Error: must fall back to non-transactional locks.
    -1                  Error: no recovery possible.
*/

int try_transactional_lock(THD *thd, TABLE_LIST *table_list)
{
  uint          dummy_counter;
  int           error;
  int           result= 0;
  DBUG_ENTER("try_transactional_lock");

  /* Need to open the tables to be able to access engine methods. */
  if (open_tables(thd, &table_list, &dummy_counter, 0))
  {
    /* purecov: begin tested */
    DBUG_PRINT("lock_info", ("aborting, open_tables failed"));
    DBUG_RETURN(-1);
    /* purecov: end */
  }

  /* Required by InnoDB. */
  thd->in_lock_tables= TRUE;

  if ((error= set_handler_table_locks(thd, table_list, TRUE)))
  {
    /*
      Not all transactional locks could be taken. If the error was
      something else but "unsupported by storage engine", abort the
      execution of this statement.
    */
    if (error != HA_ERR_WRONG_COMMAND)
    {
      DBUG_PRINT("lock_info", ("aborting, lock_table failed"));
      result= -1;
      goto err;
    }
    /*
      Fall back to non-transactional locks because transactional locks
      are unsupported by a storage engine. No need to unlock the
      successfully taken transactional locks. They go away at end of
      transaction anyway.
    */
    DBUG_PRINT("lock_info", ("fall back to non-trans lock: no SE support"));
    result= 1;
  }

 err:
  /* We need to explicitly commit if autocommit mode is active. */
  (void) ha_autocommit_or_rollback(thd, 0);
  /* Close the tables. The locks (if taken) persist in the storage engines. */
  close_tables_for_reopen(thd, &table_list);
  thd->in_lock_tables= FALSE;
  DBUG_PRINT("lock_info", ("result: %d", result));
  DBUG_RETURN(result);
}


/*
  Check if lock method conversion was done and was allowed.

  SYNOPSIS
    check_transactional_lock()
      thd                       Thread handle
      table_list                List of tables to lock

  DESCRIPTION

    Lock method conversion can be done during parsing if one of the
    locks is non-transactional. It can also happen if non-transactional
    table locks exist when the statement is executed or if a storage
    engine does not support transactional table locks.

    Check if transactional table locks have been converted to
    non-transactional and if this was allowed. In a running transaction
    or in strict mode lock method conversion is not allowed - report an
    error. Otherwise it is allowed - issue a warning.

  RETURN
    0                   OK. Proceed with non-transactional locks.
    -1                  Error: Lock conversion is prohibited.
*/

int check_transactional_lock(THD *thd, TABLE_LIST *table_list)
{
  TABLE_LIST    *tlist;
  int           result= 0;
  char          warn_buff[MYSQL_ERRMSG_SIZE];
  DBUG_ENTER("check_transactional_lock");

  for (tlist= table_list; tlist; tlist= tlist->next_global)
  {
    DBUG_PRINT("lock_info", ("checking table: '%s'", tlist->table_name));

    /*
      Unfortunately we cannot use tlist->placeholder() here. This method
      returns TRUE if the table is not open, which is always the case
      here. Whenever the definition of TABLE_LIST::placeholder() is
      changed, probably this condition needs to be changed too.
    */
    if (tlist->derived || tlist->schema_table || !tlist->lock_transactional)
    {
      DBUG_PRINT("lock_info", ("skipping placeholder: %d  transactional: %d",
                               tlist->placeholder(),
                               tlist->lock_transactional));
      continue;
    }

    /* We must not convert the lock method in strict mode. */
    {
      my_error(ER_NO_AUTO_CONVERT_LOCK_STRICT, MYF(0),
               tlist->alias ? tlist->alias : tlist->table_name);
      result= -1;
      continue;
    }

    /* We must not convert the lock method within an active transaction. */
    if (thd->active_transaction())
    {
      my_error(ER_NO_AUTO_CONVERT_LOCK_TRANSACTION, MYF(0),
               tlist->alias ? tlist->alias : tlist->table_name);
      result= -1;
      continue;
    }

    /* Warn about the conversion. */
    my_snprintf(warn_buff, sizeof(warn_buff), ER(ER_WARN_AUTO_CONVERT_LOCK),
                tlist->alias ? tlist->alias : tlist->table_name);
    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                 ER_WARN_AUTO_CONVERT_LOCK, warn_buff);
  }

  DBUG_PRINT("lock_info", ("result: %d", result));
  DBUG_RETURN(result);
}


/*
  Set table locks in the table handler.

  SYNOPSIS
    set_handler_table_locks()
      thd                       Thread handle
      table_list                List of tables to lock
      transactional             If to lock transactional or non-transactional

  RETURN
    0                   OK.
    != 0                Error code from handler::lock_table().
*/

int set_handler_table_locks(THD *thd, TABLE_LIST *table_list,
                            bool transactional)
{
  TABLE_LIST    *tlist;
  int           error= 0;
  DBUG_ENTER("set_handler_table_locks");
  DBUG_PRINT("lock_info", ("transactional: %d", transactional));

  for (tlist= table_list; tlist; tlist= tlist->next_global)
  {
    int lock_type;
    int lock_timeout= -1; /* Use default for non-transactional locks. */

    if (tlist->placeholder())
      continue;

    DBUG_ASSERT((tlist->lock_type == TL_READ) ||
                (tlist->lock_type == TL_READ_NO_INSERT) ||
                (tlist->lock_type == TL_WRITE_DEFAULT) ||
                (tlist->lock_type == TL_WRITE) ||
                (tlist->lock_type == TL_WRITE_LOW_PRIORITY));

    /*
      Every tlist object has a proper lock_type set. Even if it came in
      the list as a base table from a view only.
    */
    lock_type= ((tlist->lock_type <= TL_READ_NO_INSERT) ?
                HA_LOCK_IN_SHARE_MODE : HA_LOCK_IN_EXCLUSIVE_MODE);

    if (transactional)
    {
      /*
        The lock timeout is not set if this table belongs to a view. We
        need to take it from the top-level view. After this loop
        iteration, lock_timeout is not needed any more. Not even if the
        locks are converted to non-transactional locks later.
        Non-transactional locks do not support a lock_timeout.
      */
      lock_timeout= tlist->top_table()->lock_timeout;
      DBUG_PRINT("lock_info",
                 ("table: '%s'  tlist==top_table: %d  lock_timeout: %d",
                  tlist->table_name, tlist==tlist->top_table(), lock_timeout));

      /*
        For warning/error reporting we need to set the intended lock
        method in the TABLE_LIST object. It will be used later by
        check_transactional_lock(). The lock method is not set if this
        table belongs to a view. We can safely set it to transactional
        locking here. Even for non-view tables. This function is not
        called if non-transactional locking was requested for any
        object.
      */
      tlist->lock_transactional= TRUE;
    }

    /*
      Because we need to set the lock method (see above) for all
      involved tables, we cannot break the loop on an error.
      But we do not try more locks after the first error.
      However, for non-transactional locking handler::lock_table() is
      a hint only. So we continue to call it for other tables.
    */
    if (!error || !transactional)
    {
      error= tlist->table->file->lock_table(thd, lock_type, lock_timeout);
      if (error && transactional && (error != HA_ERR_WRONG_COMMAND))
        tlist->table->file->print_error(error, MYF(0));
    }
  }

  DBUG_RETURN(error);
}


/**
  @} (end of group Locking)
*/