ctdb/server/ctdb_lock.c

   1 /*
   2    ctdb lock handling
   3    provide API to do non-blocking locks for single or all databases
   4
   5    Copyright (C) Amitay Isaacs  2012
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, see <http://www.gnu.org/licenses/>.
  19 */
  20 #include "includes.h"
  21 #include "include/ctdb_private.h"
  22 #include "include/ctdb_protocol.h"
  23 #include "tevent.h"
  24 #include "tdb.h"
  25 #include "lib/tdb_wrap/tdb_wrap.h"
  26 #include "system/filesys.h"
  27 #include "lib/util/dlinklist.h"
  28
  29 /*
  30  * Non-blocking Locking API
  31  *
  32  * 1. Create a child process to do blocking locks.
  33  * 2. Once the locks are obtained, signal parent process via fd.
  34  * 3. Invoke registered callback routine with locking status.
  35  * 4. If the child process cannot get locks within certain time,
  36  *    execute an external script to debug.
  37  *
  38  * ctdb_lock_record()      - get a lock on a record
  39  * ctdb_lock_db()          - get a lock on a DB
  40  * ctdb_lock_alldb_prio()  - get a lock on all DBs with given priority
  41  * ctdb_lock_alldb()       - get a lock on all DBs
  42  *
  43  *  auto_mark              - whether to mark/unmark DBs in before/after callback
  44  *                           = false is used for freezing databases for
  45  *                           recovery since the recovery cannot start till
  46  *                           databases are locked on all the nodes.
  47  *                           = true is used for record locks.
  48  */
  49
  50 enum lock_type {
  51         LOCK_RECORD,
  52         LOCK_DB,
  53         LOCK_ALLDB_PRIO,
  54         LOCK_ALLDB,
  55 };
  56
  57 static const char * const lock_type_str[] = {
  58         "lock_record",
  59         "lock_db",
  60         "lock_alldb_prio",
  61         "lock_alldb",
  62 };
  63
  64 struct lock_request;
  65
  66 /* lock_context is the common part for a lock request */
  67 struct lock_context {
  68         struct lock_context *next, *prev;
  69         enum lock_type type;
  70         struct ctdb_context *ctdb;
  71         struct ctdb_db_context *ctdb_db;
  72         TDB_DATA key;
  73         uint32_t priority;
  74         bool auto_mark;
  75         struct lock_request *request;
  76         pid_t child;
  77         int fd[2];
  78         struct tevent_fd *tfd;
  79         struct tevent_timer *ttimer;
  80         struct timeval start_time;
  81         uint32_t key_hash;
  82         bool can_schedule;
  83 };
  84
  85 /* lock_request is the client specific part for a lock request */
  86 struct lock_request {
  87         struct lock_context *lctx;
  88         void (*callback)(void *, bool);
  89         void *private_data;
  90 };
  91
  92
  93 /*
  94  * Support samba 3.6.x (and older) versions which do not set db priority.
  95  *
  96  * By default, all databases are set to priority 1. So only when priority
  97  * is set to 1, check for databases that need higher priority.
  98  */
  99 static bool later_db(struct ctdb_context *ctdb, const char *name)
 100 {
 101         if (ctdb->tunable.samba3_hack == 0) {
 102                 return false;
 103         }
 104
 105         if (strstr(name, "brlock") ||
 106             strstr(name, "g_lock") ||
 107             strstr(name, "notify_onelevel") ||
 108             strstr(name, "serverid") ||
 109             strstr(name, "xattr_tdb")) {
 110                 return true;
 111         }
 112
 113         return false;
 114 }
 115
 116 typedef int (*db_handler_t)(struct ctdb_db_context *ctdb_db,
 117                             uint32_t priority,
 118                             void *private_data);
 119
 120 static int ctdb_db_iterator(struct ctdb_context *ctdb, uint32_t priority,
 121                             db_handler_t handler, void *private_data)
 122 {
 123         struct ctdb_db_context *ctdb_db;
 124         int ret;
 125
 126         for (ctdb_db = ctdb->db_list; ctdb_db; ctdb_db = ctdb_db->next) {
 127                 if (ctdb_db->priority != priority) {
 128                         continue;
 129                 }
 130                 if (later_db(ctdb, ctdb_db->db_name)) {
 131                         continue;
 132                 }
 133                 ret = handler(ctdb_db, priority, private_data);
 134                 if (ret != 0) {
 135                         return -1;
 136                 }
 137         }
 138
 139         /* If priority != 1, later_db check is not required and can return */
 140         if (priority != 1) {
 141                 return 0;
 142         }
 143
 144         for (ctdb_db = ctdb->db_list; ctdb_db; ctdb_db = ctdb_db->next) {
 145                 if (!later_db(ctdb, ctdb_db->db_name)) {
 146                         continue;
 147                 }
 148                 ret = handler(ctdb_db, priority, private_data);
 149                 if (ret != 0) {
 150                         return -1;
 151                 }
 152         }
 153
 154         return 0;
 155 }
 156
 157
 158 /*
 159  * lock all databases - mark only
 160  */
 161 static int db_lock_mark_handler(struct ctdb_db_context *ctdb_db, uint32_t priority,
 162                                 void *private_data)
 163 {
 164         int tdb_transaction_write_lock_mark(struct tdb_context *);
 165
 166         DEBUG(DEBUG_INFO, ("marking locked database %s, priority:%u\n",
 167                            ctdb_db->db_name, priority));
 168
 169         if (tdb_transaction_write_lock_mark(ctdb_db->ltdb->tdb) != 0) {
 170                 DEBUG(DEBUG_ERR, ("Failed to mark (transaction lock) database %s\n",
 171                                   ctdb_db->db_name));
 172                 return -1;
 173         }
 174
 175         if (tdb_lockall_mark(ctdb_db->ltdb->tdb) != 0) {
 176                 DEBUG(DEBUG_ERR, ("Failed to mark (all lock) database %s\n",
 177                                   ctdb_db->db_name));
 178                 return -1;
 179         }
 180
 181         return 0;
 182 }
 183
 184 int ctdb_lockall_mark_prio(struct ctdb_context *ctdb, uint32_t priority)
 185 {
 186         /*
 187          * This function is only used by the main dameon during recovery.
 188          * At this stage, the databases have already been locked, by a
 189          * dedicated child process. The freeze_mode variable is used to track
 190          * whether the actual locks are held by the child process or not.
 191          */
 192
 193         if (ctdb->freeze_mode[priority] != CTDB_FREEZE_FROZEN) {
 194                 DEBUG(DEBUG_ERR, ("Attempt to mark all databases locked when not frozen\n"));
 195                 return -1;
 196         }
 197
 198         return ctdb_db_iterator(ctdb, priority, db_lock_mark_handler, NULL);
 199 }
 200
 201 static int ctdb_lockall_mark(struct ctdb_context *ctdb)
 202 {
 203         uint32_t priority;
 204
 205         for (priority=1; priority<=NUM_DB_PRIORITIES; priority++) {
 206                 if (ctdb_db_iterator(ctdb, priority, db_lock_mark_handler, NULL) != 0) {
 207                         return -1;
 208                 }
 209         }
 210
 211         return 0;
 212 }
 213
 214
 215 /*
 216  * lock all databases - unmark only
 217  */
 218 static int db_lock_unmark_handler(struct ctdb_db_context *ctdb_db, uint32_t priority,
 219                                   void *private_data)
 220 {
 221         int tdb_transaction_write_lock_unmark(struct tdb_context *);
 222
 223         DEBUG(DEBUG_INFO, ("unmarking locked database %s, priority:%u\n",
 224                            ctdb_db->db_name, priority));
 225
 226         if (tdb_transaction_write_lock_unmark(ctdb_db->ltdb->tdb) != 0) {
 227                 DEBUG(DEBUG_ERR, ("Failed to unmark (transaction lock) database %s\n",
 228                                   ctdb_db->db_name));
 229                 return -1;
 230         }
 231
 232         if (tdb_lockall_unmark(ctdb_db->ltdb->tdb) != 0) {
 233                 DEBUG(DEBUG_ERR, ("Failed to unmark (all lock) database %s\n",
 234                                   ctdb_db->db_name));
 235                 return -1;
 236         }
 237
 238         return 0;
 239 }
 240
 241 int ctdb_lockall_unmark_prio(struct ctdb_context *ctdb, uint32_t priority)
 242 {
 243         /*
 244          * This function is only used by the main daemon during recovery.
 245          * At this stage, the databases have already been locked, by a
 246          * dedicated child process. The freeze_mode variable is used to track
 247          * whether the actual locks are held by the child process or not.
 248          */
 249
 250         if (ctdb->freeze_mode[priority] != CTDB_FREEZE_FROZEN) {
 251                 DEBUG(DEBUG_ERR, ("Attempt to unmark all databases locked when not frozen\n"));
 252                 return -1;
 253         }
 254
 255         return ctdb_db_iterator(ctdb, priority, db_lock_unmark_handler, NULL);
 256 }
 257
 258 static int ctdb_lockall_unmark(struct ctdb_context *ctdb)
 259 {
 260         uint32_t priority;
 261
 262         for (priority=NUM_DB_PRIORITIES; priority>0; priority--) {
 263                 if (ctdb_db_iterator(ctdb, priority, db_lock_unmark_handler, NULL) != 0) {
 264                         return -1;
 265                 }
 266         }
 267
 268         return 0;
 269 }
 270
 271
 272 static void ctdb_lock_schedule(struct ctdb_context *ctdb);
 273
 274 /*
 275  * Destructor to kill the child locking process
 276  */
 277 static int ctdb_lock_context_destructor(struct lock_context *lock_ctx)
 278 {
 279         if (lock_ctx->request) {
 280                 lock_ctx->request->lctx = NULL;
 281         }
 282         if (lock_ctx->child > 0) {
 283                 ctdb_kill(lock_ctx->ctdb, lock_ctx->child, SIGKILL);
 284                 if (lock_ctx->type == LOCK_RECORD) {
 285                         DLIST_REMOVE(lock_ctx->ctdb_db->lock_current, lock_ctx);
 286                 } else {
 287                         DLIST_REMOVE(lock_ctx->ctdb->lock_current, lock_ctx);
 288                 }
 289                 if (lock_ctx->ctdb_db) {
 290                         lock_ctx->ctdb_db->lock_num_current--;
 291                 }
 292                 CTDB_DECREMENT_STAT(lock_ctx->ctdb, locks.num_current);
 293                 if (lock_ctx->ctdb_db) {
 294                         CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_current);
 295                 }
 296         } else {
 297                 if (lock_ctx->type == LOCK_RECORD) {
 298                         DLIST_REMOVE(lock_ctx->ctdb_db->lock_pending, lock_ctx);
 299                 } else {
 300                         DLIST_REMOVE(lock_ctx->ctdb->lock_pending, lock_ctx);
 301                 }
 302                 CTDB_DECREMENT_STAT(lock_ctx->ctdb, locks.num_pending);
 303                 if (lock_ctx->ctdb_db) {
 304                         CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_pending);
 305                 }
 306         }
 307
 308         ctdb_lock_schedule(lock_ctx->ctdb);
 309
 310         return 0;
 311 }
 312
 313
 314 /*
 315  * Destructor to remove lock request
 316  */
 317 static int ctdb_lock_request_destructor(struct lock_request *lock_request)
 318 {
 319         if (lock_request->lctx == NULL) {
 320                 return 0;
 321         }
 322
 323         lock_request->lctx->request = NULL;
 324         TALLOC_FREE(lock_request->lctx);
 325
 326         return 0;
 327 }
 328
 329 /*
 330  * Process all the callbacks waiting for lock
 331  *
 332  * If lock has failed, callback is executed with locked=false
 333  */
 334 static void process_callbacks(struct lock_context *lock_ctx, bool locked)
 335 {
 336         struct lock_request *request;
 337         bool auto_mark = lock_ctx->auto_mark;
 338
 339         if (auto_mark && locked) {
 340                 switch (lock_ctx->type) {
 341                 case LOCK_RECORD:
 342                         tdb_chainlock_mark(lock_ctx->ctdb_db->ltdb->tdb, lock_ctx->key);
 343                         break;
 344
 345                 case LOCK_DB:
 346                         tdb_lockall_mark(lock_ctx->ctdb_db->ltdb->tdb);
 347                         break;
 348
 349                 case LOCK_ALLDB_PRIO:
 350                         ctdb_lockall_mark_prio(lock_ctx->ctdb, lock_ctx->priority);
 351                         break;
 352
 353                 case LOCK_ALLDB:
 354                         ctdb_lockall_mark(lock_ctx->ctdb);
 355                         break;
 356                 }
 357         }
 358
 359         request = lock_ctx->request;
 360         if (auto_mark) {
 361                 /* Since request may be freed in the callback, unset the lock
 362                  * context, so request destructor will not free lock context.
 363                  */
 364                 request->lctx = NULL;
 365         }
 366
 367         /* Since request may be freed in the callback, unset the request */
 368         lock_ctx->request = NULL;
 369
 370         request->callback(request->private_data, locked);
 371
 372         if (!auto_mark) {
 373                 return;
 374         }
 375
 376         if (locked) {
 377                 switch (lock_ctx->type) {
 378                 case LOCK_RECORD:
 379                         tdb_chainlock_unmark(lock_ctx->ctdb_db->ltdb->tdb, lock_ctx->key);
 380                         break;
 381
 382                 case LOCK_DB:
 383                         tdb_lockall_unmark(lock_ctx->ctdb_db->ltdb->tdb);
 384                         break;
 385
 386                 case LOCK_ALLDB_PRIO:
 387                         ctdb_lockall_unmark_prio(lock_ctx->ctdb, lock_ctx->priority);
 388                         break;
 389
 390                 case LOCK_ALLDB:
 391                         ctdb_lockall_unmark(lock_ctx->ctdb);
 392                         break;
 393                 }
 394         }
 395
 396         talloc_free(lock_ctx);
 397 }
 398
 399
 400 static int lock_bucket_id(double t)
 401 {
 402         double ms = 1.e-3, s = 1;
 403         int id;
 404
 405         if (t < 1*ms) {
 406                 id = 0;
 407         } else if (t < 10*ms) {
 408                 id = 1;
 409         } else if (t < 100*ms) {
 410                 id = 2;
 411         } else if (t < 1*s) {
 412                 id = 3;
 413         } else if (t < 2*s) {
 414                 id = 4;
 415         } else if (t < 4*s) {
 416                 id = 5;
 417         } else if (t < 8*s) {
 418                 id = 6;
 419         } else if (t < 16*s) {
 420                 id = 7;
 421         } else if (t < 32*s) {
 422                 id = 8;
 423         } else if (t < 64*s) {
 424                 id = 9;
 425         } else {
 426                 id = 10;
 427         }
 428
 429         return id;
 430 }
 431
 432 /*
 433  * Callback routine when the required locks are obtained.
 434  * Called from parent context
 435  */
 436 static void ctdb_lock_handler(struct tevent_context *ev,
 437                             struct tevent_fd *tfd,
 438                             uint16_t flags,
 439                             void *private_data)
 440 {
 441         struct lock_context *lock_ctx;
 442         char c;
 443         bool locked;
 444         double t;
 445         int id;
 446
 447         lock_ctx = talloc_get_type_abort(private_data, struct lock_context);
 448
 449         /* cancel the timeout event */
 450         TALLOC_FREE(lock_ctx->ttimer);
 451
 452         t = timeval_elapsed(&lock_ctx->start_time);
 453         id = lock_bucket_id(t);
 454
 455         /* Read the status from the child process */
 456         if (sys_read(lock_ctx->fd[0], &c, 1) != 1) {
 457                 locked = false;
 458         } else {
 459                 locked = (c == 0 ? true : false);
 460         }
 461
 462         /* Update statistics */
 463         CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.num_calls);
 464         if (lock_ctx->ctdb_db) {
 465                 CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_calls);
 466         }
 467
 468         if (locked) {
 469                 if (lock_ctx->ctdb_db) {
 470                         CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.buckets[id]);
 471                         CTDB_UPDATE_LATENCY(lock_ctx->ctdb, lock_ctx->ctdb_db,
 472                                             lock_type_str[lock_ctx->type], locks.latency,
 473                                             lock_ctx->start_time);
 474
 475                         CTDB_UPDATE_DB_LATENCY(lock_ctx->ctdb_db, lock_type_str[lock_ctx->type], locks.latency, t);
 476                         CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.buckets[id]);
 477                 }
 478         } else {
 479                 CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.num_failed);
 480                 if (lock_ctx->ctdb_db) {
 481                         CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_failed);
 482                 }
 483         }
 484
 485         process_callbacks(lock_ctx, locked);
 486 }
 487
 488
 489 /*
 490  * Callback routine when required locks are not obtained within timeout
 491  * Called from parent context
 492  */
 493 static void ctdb_lock_timeout_handler(struct tevent_context *ev,
 494                                     struct tevent_timer *ttimer,
 495                                     struct timeval current_time,
 496                                     void *private_data)
 497 {
 498         static const char * debug_locks = NULL;
 499         struct lock_context *lock_ctx;
 500         struct ctdb_context *ctdb;
 501         pid_t pid;
 502
 503         lock_ctx = talloc_get_type_abort(private_data, struct lock_context);
 504         ctdb = lock_ctx->ctdb;
 505
 506         /* If a node stopped/banned, don't spam the logs */
 507         if (ctdb->nodes[ctdb->pnn]->flags & NODE_FLAGS_INACTIVE) {
 508                 lock_ctx->ttimer = NULL;
 509                 return;
 510         }
 511         if (lock_ctx->ctdb_db) {
 512                 DEBUG(DEBUG_WARNING,
 513                       ("Unable to get %s lock on database %s for %.0lf seconds\n",
 514                        (lock_ctx->type == LOCK_RECORD ? "RECORD" : "DB"),
 515                        lock_ctx->ctdb_db->db_name,
 516                        timeval_elapsed(&lock_ctx->start_time)));
 517         } else {
 518                 DEBUG(DEBUG_WARNING,
 519                       ("Unable to get ALLDB locks for %.0lf seconds\n",
 520                        timeval_elapsed(&lock_ctx->start_time)));
 521         }
 522
 523         /* Fire a child process to find the blocking process. */
 524         if (debug_locks == NULL) {
 525                 debug_locks = getenv("CTDB_DEBUG_LOCKS");
 526                 if (debug_locks == NULL) {
 527                         debug_locks = talloc_asprintf(ctdb,
 528                                                       "%s/debug_locks.sh",
 529                                                       getenv("CTDB_BASE"));
 530                 }
 531         }
 532         if (debug_locks != NULL) {
 533                 pid = vfork();
 534                 if (pid == 0) {
 535                         execl(debug_locks, debug_locks, NULL);
 536                         _exit(0);
 537                 }
 538                 ctdb_track_child(ctdb, pid);
 539         } else {
 540                 DEBUG(DEBUG_WARNING,
 541                       (__location__
 542                        " Unable to setup lock debugging - no memory?\n"));
 543         }
 544
 545         /* reset the timeout timer */
 546         // talloc_free(lock_ctx->ttimer);
 547         lock_ctx->ttimer = tevent_add_timer(ctdb->ev,
 548                                             lock_ctx,
 549                                             timeval_current_ofs(10, 0),
 550                                             ctdb_lock_timeout_handler,
 551                                             (void *)lock_ctx);
 552 }
 553
 554
 555 static int db_count_handler(struct ctdb_db_context *ctdb_db, uint32_t priority,
 556                             void *private_data)
 557 {
 558         int *count = (int *)private_data;
 559
 560         (*count) += 2;
 561
 562         return 0;
 563 }
 564
 565 static int db_flags(struct ctdb_db_context *ctdb_db)
 566 {
 567         int tdb_flags = TDB_DEFAULT;
 568
 569 #ifdef TDB_MUTEX_LOCKING
 570         if (!ctdb_db->persistent && ctdb_db->ctdb->tunable.mutex_enabled) {
 571                 tdb_flags = (TDB_MUTEX_LOCKING | TDB_CLEAR_IF_FIRST);
 572         }
 573 #endif
 574         return tdb_flags;
 575 }
 576
 577 struct db_namelist {
 578         const char **names;
 579         int n;
 580 };
 581
 582 static int db_name_handler(struct ctdb_db_context *ctdb_db, uint32_t priority,
 583                            void *private_data)
 584 {
 585         struct db_namelist *list = (struct db_namelist *)private_data;
 586
 587         list->names[list->n] = talloc_strdup(list->names, ctdb_db->db_path);
 588         list->names[list->n+1] = talloc_asprintf(list->names, "0x%x",
 589                                                  db_flags(ctdb_db));
 590         list->n += 2;
 591
 592         return 0;
 593 }
 594
 595 static bool lock_helper_args(TALLOC_CTX *mem_ctx,
 596                              struct lock_context *lock_ctx, int fd,
 597                              int *argc, const char ***argv)
 598 {
 599         struct ctdb_context *ctdb = lock_ctx->ctdb;
 600         const char **args = NULL;
 601         int nargs, i;
 602         int priority;
 603         struct db_namelist list;
 604
 605         switch (lock_ctx->type) {
 606         case LOCK_RECORD:
 607                 nargs = 6;
 608                 break;
 609
 610         case LOCK_DB:
 611                 nargs = 5;
 612                 break;
 613
 614         case LOCK_ALLDB_PRIO:
 615                 nargs = 3;
 616                 ctdb_db_iterator(ctdb, lock_ctx->priority, db_count_handler, &nargs);
 617                 break;
 618
 619         case LOCK_ALLDB:
 620                 nargs = 3;
 621                 for (priority=1; priority<NUM_DB_PRIORITIES; priority++) {
 622                         ctdb_db_iterator(ctdb, priority, db_count_handler, &nargs);
 623                 }
 624                 break;
 625         }
 626
 627         /* Add extra argument for null termination */
 628         nargs++;
 629
 630         args = talloc_array(mem_ctx, const char *, nargs);
 631         if (args == NULL) {
 632                 return false;
 633         }
 634
 635         args[0] = talloc_asprintf(args, "%d", getpid());
 636         args[1] = talloc_asprintf(args, "%d", fd);
 637
 638         switch (lock_ctx->type) {
 639         case LOCK_RECORD:
 640                 args[2] = talloc_strdup(args, "RECORD");
 641                 args[3] = talloc_strdup(args, lock_ctx->ctdb_db->db_path);
 642                 args[4] = talloc_asprintf(args, "0x%x",
 643                                           db_flags(lock_ctx->ctdb_db));
 644                 if (lock_ctx->key.dsize == 0) {
 645                         args[5] = talloc_strdup(args, "NULL");
 646                 } else {
 647                         args[5] = hex_encode_talloc(args, lock_ctx->key.dptr, lock_ctx->key.dsize);
 648                 }
 649                 break;
 650
 651         case LOCK_DB:
 652                 args[2] = talloc_strdup(args, "DB");
 653                 args[3] = talloc_strdup(args, lock_ctx->ctdb_db->db_path);
 654                 args[4] = talloc_asprintf(args, "0x%x",
 655                                           db_flags(lock_ctx->ctdb_db));
 656                 break;
 657
 658         case LOCK_ALLDB_PRIO:
 659                 args[2] = talloc_strdup(args, "DB");
 660                 list.names = args;
 661                 list.n = 3;
 662                 ctdb_db_iterator(ctdb, lock_ctx->priority, db_name_handler, &list);
 663                 break;
 664
 665         case LOCK_ALLDB:
 666                 args[2] = talloc_strdup(args, "DB");
 667                 list.names = args;
 668                 list.n = 3;
 669                 for (priority=1; priority<NUM_DB_PRIORITIES; priority++) {
 670                         ctdb_db_iterator(ctdb, priority, db_name_handler, &list);
 671                 }
 672                 break;
 673         }
 674
 675         /* Make sure last argument is NULL */
 676         args[nargs-1] = NULL;
 677
 678         for (i=0; i<nargs-1; i++) {
 679                 if (args[i] == NULL) {
 680                         talloc_free(args);
 681                         return false;
 682                 }
 683         }
 684
 685         *argc = nargs;
 686         *argv = args;
 687         return true;
 688 }
 689
 690 /*
 691  * Find a lock request that can be scheduled
 692  */
 693 static struct lock_context *ctdb_find_lock_context(struct ctdb_context *ctdb)
 694 {
 695         struct lock_context *lock_ctx, *next_ctx;
 696         struct ctdb_db_context *ctdb_db;
 697
 698         /* First check if there are database lock requests */
 699
 700         for (lock_ctx = ctdb->lock_pending; lock_ctx != NULL;
 701              lock_ctx = next_ctx) {
 702
 703                 if (lock_ctx->request != NULL) {
 704                         /* Found a lock context with a request */
 705                         return lock_ctx;
 706                 }
 707
 708                 next_ctx = lock_ctx->next;
 709
 710                 DEBUG(DEBUG_INFO, ("Removing lock context without lock "
 711                                    "request\n"));
 712                 DLIST_REMOVE(ctdb->lock_pending, lock_ctx);
 713                 CTDB_DECREMENT_STAT(ctdb, locks.num_pending);
 714                 if (lock_ctx->ctdb_db) {
 715                         CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db,
 716                                                locks.num_pending);
 717                 }
 718                 talloc_free(lock_ctx);
 719         }
 720
 721         /* Next check database queues */
 722         for (ctdb_db = ctdb->db_list; ctdb_db; ctdb_db = ctdb_db->next) {
 723                 if (ctdb_db->lock_num_current ==
 724                     ctdb->tunable.lock_processes_per_db) {
 725                         continue;
 726                 }
 727
 728                 for (lock_ctx = ctdb_db->lock_pending; lock_ctx != NULL;
 729                      lock_ctx = next_ctx) {
 730
 731                         next_ctx = lock_ctx->next;
 732
 733                         if (lock_ctx->request != NULL) {
 734                                 return lock_ctx;
 735                         }
 736
 737                         DEBUG(DEBUG_INFO, ("Removing lock context without "
 738                                            "lock request\n"));
 739                         DLIST_REMOVE(ctdb_db->lock_pending, lock_ctx);
 740                         CTDB_DECREMENT_STAT(ctdb, locks.num_pending);
 741                         CTDB_DECREMENT_DB_STAT(ctdb_db, locks.num_pending);
 742                         talloc_free(lock_ctx);
 743                 }
 744         }
 745
 746         return NULL;
 747 }
 748
 749 /*
 750  * Schedule a new lock child process
 751  * Set up callback handler and timeout handler
 752  */
 753 static void ctdb_lock_schedule(struct ctdb_context *ctdb)
 754 {
 755         struct lock_context *lock_ctx;
 756         int ret, argc;
 757         TALLOC_CTX *tmp_ctx;
 758         const char *helper = CTDB_HELPER_BINDIR "/ctdb_lock_helper";
 759         static const char *prog = NULL;
 760         const char **args;
 761
 762         if (prog == NULL) {
 763                 const char *t;
 764
 765                 t = getenv("CTDB_LOCK_HELPER");
 766                 if (t != NULL) {
 767                         prog = talloc_strdup(ctdb, t);
 768                 } else {
 769                         prog = talloc_strdup(ctdb, helper);
 770                 }
 771                 CTDB_NO_MEMORY_VOID(ctdb, prog);
 772         }
 773
 774         /* Find a lock context with requests */
 775         lock_ctx = ctdb_find_lock_context(ctdb);
 776         if (lock_ctx == NULL) {
 777                 return;
 778         }
 779
 780         lock_ctx->child = -1;
 781         ret = pipe(lock_ctx->fd);
 782         if (ret != 0) {
 783                 DEBUG(DEBUG_ERR, ("Failed to create pipe in ctdb_lock_schedule\n"));
 784                 return;
 785         }
 786
 787         set_close_on_exec(lock_ctx->fd[0]);
 788
 789         /* Create data for child process */
 790         tmp_ctx = talloc_new(lock_ctx);
 791         if (tmp_ctx == NULL) {
 792                 DEBUG(DEBUG_ERR, ("Failed to allocate memory for helper args\n"));
 793                 close(lock_ctx->fd[0]);
 794                 close(lock_ctx->fd[1]);
 795                 return;
 796         }
 797
 798         /* Create arguments for lock helper */
 799         if (!lock_helper_args(tmp_ctx, lock_ctx, lock_ctx->fd[1],
 800                               &argc, &args)) {
 801                 DEBUG(DEBUG_ERR, ("Failed to create lock helper args\n"));
 802                 close(lock_ctx->fd[0]);
 803                 close(lock_ctx->fd[1]);
 804                 talloc_free(tmp_ctx);
 805                 return;
 806         }
 807
 808         if (!ctdb_vfork_with_logging(lock_ctx, ctdb, "lock_helper",
 809                                      prog, argc, (const char **)args,
 810                                      NULL, NULL, &lock_ctx->child)) {
 811                 DEBUG(DEBUG_ERR, ("Failed to create a child in ctdb_lock_schedule\n"));
 812                 close(lock_ctx->fd[0]);
 813                 close(lock_ctx->fd[1]);
 814                 talloc_free(tmp_ctx);
 815                 return;
 816         }
 817
 818         /* Parent process */
 819         close(lock_ctx->fd[1]);
 820
 821         talloc_free(tmp_ctx);
 822
 823         /* Set up timeout handler */
 824         lock_ctx->ttimer = tevent_add_timer(ctdb->ev,
 825                                             lock_ctx,
 826                                             timeval_current_ofs(10, 0),
 827                                             ctdb_lock_timeout_handler,
 828                                             (void *)lock_ctx);
 829         if (lock_ctx->ttimer == NULL) {
 830                 ctdb_kill(ctdb, lock_ctx->child, SIGKILL);
 831                 lock_ctx->child = -1;
 832                 close(lock_ctx->fd[0]);
 833                 return;
 834         }
 835
 836         /* Set up callback */
 837         lock_ctx->tfd = tevent_add_fd(ctdb->ev,
 838                                       lock_ctx,
 839                                       lock_ctx->fd[0],
 840                                       EVENT_FD_READ,
 841                                       ctdb_lock_handler,
 842                                       (void *)lock_ctx);
 843         if (lock_ctx->tfd == NULL) {
 844                 TALLOC_FREE(lock_ctx->ttimer);
 845                 ctdb_kill(ctdb, lock_ctx->child, SIGKILL);
 846                 lock_ctx->child = -1;
 847                 close(lock_ctx->fd[0]);
 848                 return;
 849         }
 850         tevent_fd_set_auto_close(lock_ctx->tfd);
 851
 852         /* Move the context from pending to current */
 853         if (lock_ctx->type == LOCK_RECORD) {
 854                 DLIST_REMOVE(lock_ctx->ctdb_db->lock_pending, lock_ctx);
 855                 DLIST_ADD_END(lock_ctx->ctdb_db->lock_current, lock_ctx, NULL);
 856         } else {
 857                 DLIST_REMOVE(ctdb->lock_pending, lock_ctx);
 858                 DLIST_ADD_END(ctdb->lock_current, lock_ctx, NULL);
 859         }
 860         CTDB_DECREMENT_STAT(lock_ctx->ctdb, locks.num_pending);
 861         CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.num_current);
 862         if (lock_ctx->ctdb_db) {
 863                 lock_ctx->ctdb_db->lock_num_current++;
 864                 CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_pending);
 865                 CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_current);
 866         }
 867 }
 868
 869
 870 /*
 871  * Lock record / db depending on type
 872  */
 873 static struct lock_request *ctdb_lock_internal(TALLOC_CTX *mem_ctx,
 874                                                struct ctdb_context *ctdb,
 875                                                struct ctdb_db_context *ctdb_db,
 876                                                TDB_DATA key,
 877                                                uint32_t priority,
 878                                                void (*callback)(void *, bool),
 879                                                void *private_data,
 880                                                enum lock_type type,
 881                                                bool auto_mark)
 882 {
 883         struct lock_context *lock_ctx = NULL;
 884         struct lock_request *request;
 885
 886         if (callback == NULL) {
 887                 DEBUG(DEBUG_WARNING, ("No callback function specified, not locking\n"));
 888                 return NULL;
 889         }
 890
 891         lock_ctx = talloc_zero(ctdb, struct lock_context);
 892         if (lock_ctx == NULL) {
 893                 DEBUG(DEBUG_ERR, ("Failed to create a new lock context\n"));
 894                 return NULL;
 895         }
 896
 897         if ((request = talloc_zero(mem_ctx, struct lock_request)) == NULL) {
 898                 talloc_free(lock_ctx);
 899                 return NULL;
 900         }
 901
 902         lock_ctx->type = type;
 903         lock_ctx->ctdb = ctdb;
 904         lock_ctx->ctdb_db = ctdb_db;
 905         lock_ctx->key.dsize = key.dsize;
 906         if (key.dsize > 0) {
 907                 lock_ctx->key.dptr = talloc_memdup(lock_ctx, key.dptr, key.dsize);
 908                 if (lock_ctx->key.dptr == NULL) {
 909                         DEBUG(DEBUG_ERR, (__location__ "Memory allocation error\n"));
 910                         talloc_free(lock_ctx);
 911                         talloc_free(request);
 912                         return NULL;
 913                 }
 914                 lock_ctx->key_hash = ctdb_hash(&key);
 915         } else {
 916                 lock_ctx->key.dptr = NULL;
 917         }
 918         lock_ctx->priority = priority;
 919         lock_ctx->auto_mark = auto_mark;
 920
 921         lock_ctx->request = request;
 922         lock_ctx->child = -1;
 923
 924         /* Non-record locks are required by recovery and should be scheduled
 925          * immediately, so keep them at the head of the pending queue.
 926          */
 927         if (lock_ctx->type == LOCK_RECORD) {
 928                 DLIST_ADD_END(ctdb_db->lock_pending, lock_ctx, NULL);
 929         } else {
 930                 DLIST_ADD_END(ctdb->lock_pending, lock_ctx, NULL);
 931         }
 932         CTDB_INCREMENT_STAT(ctdb, locks.num_pending);
 933         if (ctdb_db) {
 934                 CTDB_INCREMENT_DB_STAT(ctdb_db, locks.num_pending);
 935         }
 936
 937         /* Start the timer when we activate the context */
 938         lock_ctx->start_time = timeval_current();
 939
 940         request->lctx = lock_ctx;
 941         request->callback = callback;
 942         request->private_data = private_data;
 943
 944         talloc_set_destructor(request, ctdb_lock_request_destructor);
 945         talloc_set_destructor(lock_ctx, ctdb_lock_context_destructor);
 946
 947         ctdb_lock_schedule(ctdb);
 948
 949         return request;
 950 }
 951
 952
 953 /*
 954  * obtain a lock on a record in a database
 955  */
 956 struct lock_request *ctdb_lock_record(TALLOC_CTX *mem_ctx,
 957                                       struct ctdb_db_context *ctdb_db,
 958                                       TDB_DATA key,
 959                                       bool auto_mark,
 960                                       void (*callback)(void *, bool),
 961                                       void *private_data)
 962 {
 963         return ctdb_lock_internal(mem_ctx,
 964                                   ctdb_db->ctdb,
 965                                   ctdb_db,
 966                                   key,
 967                                   0,
 968                                   callback,
 969                                   private_data,
 970                                   LOCK_RECORD,
 971                                   auto_mark);
 972 }
 973
 974
 975 /*
 976  * obtain a lock on a database
 977  */
 978 struct lock_request *ctdb_lock_db(TALLOC_CTX *mem_ctx,
 979                                   struct ctdb_db_context *ctdb_db,
 980                                   bool auto_mark,
 981                                   void (*callback)(void *, bool),
 982                                   void *private_data)
 983 {
 984         return ctdb_lock_internal(mem_ctx,
 985                                   ctdb_db->ctdb,
 986                                   ctdb_db,
 987                                   tdb_null,
 988                                   0,
 989                                   callback,
 990                                   private_data,
 991                                   LOCK_DB,
 992                                   auto_mark);
 993 }
 994
 995
 996 /*
 997  * obtain locks on all databases of specified priority
 998  */
 999 struct lock_request *ctdb_lock_alldb_prio(TALLOC_CTX *mem_ctx,
1000                                           struct ctdb_context *ctdb,
1001                                           uint32_t priority,
1002                                           bool auto_mark,
1003                                           void (*callback)(void *, bool),
1004                                           void *private_data)
1005 {
1006         if (priority < 1 || priority > NUM_DB_PRIORITIES) {
1007                 DEBUG(DEBUG_ERR, ("Invalid db priority: %u\n", priority));
1008                 return NULL;
1009         }
1010
1011         return ctdb_lock_internal(mem_ctx,
1012                                   ctdb,
1013                                   NULL,
1014                                   tdb_null,
1015                                   priority,
1016                                   callback,
1017                                   private_data,
1018                                   LOCK_ALLDB_PRIO,
1019                                   auto_mark);
1020 }
1021
1022
1023 /*
1024  * obtain locks on all databases
1025  */
1026 struct lock_request *ctdb_lock_alldb(TALLOC_CTX *mem_ctx,
1027                                      struct ctdb_context *ctdb,
1028                                      bool auto_mark,
1029                                      void (*callback)(void *, bool),
1030                                      void *private_data)
1031 {
1032         return ctdb_lock_internal(mem_ctx,
1033                                   ctdb,
1034                                   NULL,
1035                                   tdb_null,
1036                                   0,
1037                                   callback,
1038                                   private_data,
1039                                   LOCK_ALLDB,
1040                                   auto_mark);
1041 }
1042