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 "replace.h"
  21 #include "system/filesys.h"
  22 #include "system/network.h"
  23
  24 #include <talloc.h>
  25 #include <tevent.h>
  26
  27 #include "lib/tdb_wrap/tdb_wrap.h"
  28 #include "lib/util/dlinklist.h"
  29 #include "lib/util/debug.h"
  30 #include "lib/util/samba_util.h"
  31 #include "lib/util/sys_rw.h"
  32
  33 #include "ctdb_private.h"
  34
  35 #include "common/common.h"
  36 #include "common/logging.h"
  37
  38 /*
  39  * Non-blocking Locking API
  40  *
  41  * 1. Create a child process to do blocking locks.
  42  * 2. Once the locks are obtained, signal parent process via fd.
  43  * 3. Invoke registered callback routine with locking status.
  44  * 4. If the child process cannot get locks within certain time,
  45  *    execute an external script to debug.
  46  *
  47  * ctdb_lock_record()      - get a lock on a record
  48  * ctdb_lock_db()          - get a lock on a DB
  49  *
  50  *  auto_mark              - whether to mark/unmark DBs in before/after callback
  51  *                           = false is used for freezing databases for
  52  *                           recovery since the recovery cannot start till
  53  *                           databases are locked on all the nodes.
  54  *                           = true is used for record locks.
  55  */
  56
  57 enum lock_type {
  58         LOCK_RECORD,
  59         LOCK_DB,
  60 };
  61
  62 static const char * const lock_type_str[] = {
  63         "lock_record",
  64         "lock_db",
  65 };
  66
  67 struct lock_request;
  68
  69 /* lock_context is the common part for a lock request */
  70 struct lock_context {
  71         struct lock_context *next, *prev;
  72         enum lock_type type;
  73         struct ctdb_context *ctdb;
  74         struct ctdb_db_context *ctdb_db;
  75         TDB_DATA key;
  76         uint32_t priority;
  77         bool auto_mark;
  78         struct lock_request *request;
  79         pid_t child;
  80         int fd[2];
  81         struct tevent_fd *tfd;
  82         struct tevent_timer *ttimer;
  83         struct timeval start_time;
  84         uint32_t key_hash;
  85         bool can_schedule;
  86 };
  87
  88 /* lock_request is the client specific part for a lock request */
  89 struct lock_request {
  90         struct lock_context *lctx;
  91         void (*callback)(void *, bool);
  92         void *private_data;
  93 };
  94
  95
  96 int ctdb_db_iterator(struct ctdb_context *ctdb, ctdb_db_handler_t handler,
  97                      void *private_data)
  98 {
  99         struct ctdb_db_context *ctdb_db;
 100         int ret;
 101
 102         for (ctdb_db = ctdb->db_list; ctdb_db; ctdb_db = ctdb_db->next) {
 103                 ret = handler(ctdb_db, private_data);
 104                 if (ret != 0) {
 105                         return -1;
 106                 }
 107         }
 108
 109         return 0;
 110 }
 111
 112 /*
 113  * lock all databases - mark only
 114  */
 115 static int db_lock_mark_handler(struct ctdb_db_context *ctdb_db,
 116                                 void *private_data)
 117 {
 118         int tdb_transaction_write_lock_mark(struct tdb_context *);
 119
 120         DEBUG(DEBUG_INFO, ("marking locked database %s\n", ctdb_db->db_name));
 121
 122         if (tdb_transaction_write_lock_mark(ctdb_db->ltdb->tdb) != 0) {
 123                 DEBUG(DEBUG_ERR, ("Failed to mark (transaction lock) database %s\n",
 124                                   ctdb_db->db_name));
 125                 return -1;
 126         }
 127
 128         if (tdb_lockall_mark(ctdb_db->ltdb->tdb) != 0) {
 129                 DEBUG(DEBUG_ERR, ("Failed to mark (all lock) database %s\n",
 130                                   ctdb_db->db_name));
 131                 return -1;
 132         }
 133
 134         return 0;
 135 }
 136
 137 int ctdb_lockdb_mark(struct ctdb_db_context *ctdb_db)
 138 {
 139         if (!ctdb_db_frozen(ctdb_db)) {
 140                 DEBUG(DEBUG_ERR,
 141                       ("Attempt to mark database locked when not frozen\n"));
 142                 return -1;
 143         }
 144
 145         return db_lock_mark_handler(ctdb_db, NULL);
 146 }
 147
 148 /*
 149  * lock all databases - unmark only
 150  */
 151 static int db_lock_unmark_handler(struct ctdb_db_context *ctdb_db,
 152                                   void *private_data)
 153 {
 154         int tdb_transaction_write_lock_unmark(struct tdb_context *);
 155
 156         DEBUG(DEBUG_INFO, ("unmarking locked database %s\n", ctdb_db->db_name));
 157
 158         if (tdb_transaction_write_lock_unmark(ctdb_db->ltdb->tdb) != 0) {
 159                 DEBUG(DEBUG_ERR, ("Failed to unmark (transaction lock) database %s\n",
 160                                   ctdb_db->db_name));
 161                 return -1;
 162         }
 163
 164         if (tdb_lockall_unmark(ctdb_db->ltdb->tdb) != 0) {
 165                 DEBUG(DEBUG_ERR, ("Failed to unmark (all lock) database %s\n",
 166                                   ctdb_db->db_name));
 167                 return -1;
 168         }
 169
 170         return 0;
 171 }
 172
 173 int ctdb_lockdb_unmark(struct ctdb_db_context *ctdb_db)
 174 {
 175         if (!ctdb_db_frozen(ctdb_db)) {
 176                 DEBUG(DEBUG_ERR,
 177                       ("Attempt to unmark database locked when not frozen\n"));
 178                 return -1;
 179         }
 180
 181         return db_lock_unmark_handler(ctdb_db, NULL);
 182 }
 183
 184 static void ctdb_lock_schedule(struct ctdb_context *ctdb);
 185
 186 /*
 187  * Destructor to kill the child locking process
 188  */
 189 static int ctdb_lock_context_destructor(struct lock_context *lock_ctx)
 190 {
 191         if (lock_ctx->request) {
 192                 lock_ctx->request->lctx = NULL;
 193         }
 194         if (lock_ctx->child > 0) {
 195                 ctdb_kill(lock_ctx->ctdb, lock_ctx->child, SIGTERM);
 196                 if (lock_ctx->type == LOCK_RECORD) {
 197                         DLIST_REMOVE(lock_ctx->ctdb_db->lock_current, lock_ctx);
 198                 } else {
 199                         DLIST_REMOVE(lock_ctx->ctdb->lock_current, lock_ctx);
 200                 }
 201                 if (lock_ctx->ctdb_db) {
 202                         lock_ctx->ctdb_db->lock_num_current--;
 203                 }
 204                 CTDB_DECREMENT_STAT(lock_ctx->ctdb, locks.num_current);
 205                 if (lock_ctx->ctdb_db) {
 206                         CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_current);
 207                 }
 208         } else {
 209                 if (lock_ctx->type == LOCK_RECORD) {
 210                         DLIST_REMOVE(lock_ctx->ctdb_db->lock_pending, lock_ctx);
 211                 } else {
 212                         DLIST_REMOVE(lock_ctx->ctdb->lock_pending, lock_ctx);
 213                 }
 214                 CTDB_DECREMENT_STAT(lock_ctx->ctdb, locks.num_pending);
 215                 if (lock_ctx->ctdb_db) {
 216                         CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_pending);
 217                 }
 218         }
 219
 220         ctdb_lock_schedule(lock_ctx->ctdb);
 221
 222         return 0;
 223 }
 224
 225
 226 /*
 227  * Destructor to remove lock request
 228  */
 229 static int ctdb_lock_request_destructor(struct lock_request *lock_request)
 230 {
 231         if (lock_request->lctx == NULL) {
 232                 return 0;
 233         }
 234
 235         lock_request->lctx->request = NULL;
 236         TALLOC_FREE(lock_request->lctx);
 237
 238         return 0;
 239 }
 240
 241 /*
 242  * Process all the callbacks waiting for lock
 243  *
 244  * If lock has failed, callback is executed with locked=false
 245  */
 246 static void process_callbacks(struct lock_context *lock_ctx, bool locked)
 247 {
 248         struct lock_request *request;
 249         bool auto_mark = lock_ctx->auto_mark;
 250
 251         if (auto_mark && locked) {
 252                 switch (lock_ctx->type) {
 253                 case LOCK_RECORD:
 254                         tdb_chainlock_mark(lock_ctx->ctdb_db->ltdb->tdb, lock_ctx->key);
 255                         break;
 256
 257                 case LOCK_DB:
 258                         ctdb_lockdb_mark(lock_ctx->ctdb_db);
 259                         break;
 260                 }
 261         }
 262
 263         request = lock_ctx->request;
 264         if (auto_mark) {
 265                 /* Since request may be freed in the callback, unset the lock
 266                  * context, so request destructor will not free lock context.
 267                  */
 268                 request->lctx = NULL;
 269         }
 270
 271         /* Since request may be freed in the callback, unset the request */
 272         lock_ctx->request = NULL;
 273
 274         request->callback(request->private_data, locked);
 275
 276         if (!auto_mark) {
 277                 return;
 278         }
 279
 280         if (locked) {
 281                 switch (lock_ctx->type) {
 282                 case LOCK_RECORD:
 283                         tdb_chainlock_unmark(lock_ctx->ctdb_db->ltdb->tdb, lock_ctx->key);
 284                         break;
 285
 286                 case LOCK_DB:
 287                         ctdb_lockdb_unmark(lock_ctx->ctdb_db);
 288                         break;
 289                 }
 290         }
 291
 292         talloc_free(lock_ctx);
 293 }
 294
 295
 296 static int lock_bucket_id(double t)
 297 {
 298         double ms = 1.e-3, s = 1;
 299         int id;
 300
 301         if (t < 1*ms) {
 302                 id = 0;
 303         } else if (t < 10*ms) {
 304                 id = 1;
 305         } else if (t < 100*ms) {
 306                 id = 2;
 307         } else if (t < 1*s) {
 308                 id = 3;
 309         } else if (t < 2*s) {
 310                 id = 4;
 311         } else if (t < 4*s) {
 312                 id = 5;
 313         } else if (t < 8*s) {
 314                 id = 6;
 315         } else if (t < 16*s) {
 316                 id = 7;
 317         } else if (t < 32*s) {
 318                 id = 8;
 319         } else if (t < 64*s) {
 320                 id = 9;
 321         } else {
 322                 id = 10;
 323         }
 324
 325         return id;
 326 }
 327
 328 /*
 329  * Callback routine when the required locks are obtained.
 330  * Called from parent context
 331  */
 332 static void ctdb_lock_handler(struct tevent_context *ev,
 333                             struct tevent_fd *tfd,
 334                             uint16_t flags,
 335                             void *private_data)
 336 {
 337         struct lock_context *lock_ctx;
 338         char c;
 339         bool locked;
 340         double t;
 341         int id;
 342
 343         lock_ctx = talloc_get_type_abort(private_data, struct lock_context);
 344
 345         /* cancel the timeout event */
 346         TALLOC_FREE(lock_ctx->ttimer);
 347
 348         t = timeval_elapsed(&lock_ctx->start_time);
 349         id = lock_bucket_id(t);
 350
 351         /* Read the status from the child process */
 352         if (sys_read(lock_ctx->fd[0], &c, 1) != 1) {
 353                 locked = false;
 354         } else {
 355                 locked = (c == 0 ? true : false);
 356         }
 357
 358         /* Update statistics */
 359         CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.num_calls);
 360         if (lock_ctx->ctdb_db) {
 361                 CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_calls);
 362         }
 363
 364         if (locked) {
 365                 if (lock_ctx->ctdb_db) {
 366                         CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.buckets[id]);
 367                         CTDB_UPDATE_LATENCY(lock_ctx->ctdb, lock_ctx->ctdb_db,
 368                                             lock_type_str[lock_ctx->type], locks.latency,
 369                                             lock_ctx->start_time);
 370
 371                         CTDB_UPDATE_DB_LATENCY(lock_ctx->ctdb_db, lock_type_str[lock_ctx->type], locks.latency, t);
 372                         CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.buckets[id]);
 373                 }
 374         } else {
 375                 CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.num_failed);
 376                 if (lock_ctx->ctdb_db) {
 377                         CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_failed);
 378                 }
 379         }
 380
 381         process_callbacks(lock_ctx, locked);
 382 }
 383
 384 struct lock_log_entry {
 385         struct db_hash_context *lock_log;
 386         TDB_DATA key;
 387         unsigned long log_sec;
 388         struct tevent_timer *timer;
 389 };
 390
 391 static int lock_log_fetch_parser(uint8_t *keybuf, size_t keylen,
 392                                  uint8_t *databuf, size_t datalen,
 393                                  void *private_data)
 394 {
 395         struct lock_log_entry **entry =
 396                 (struct lock_log_entry **)private_data;
 397
 398         if (datalen != sizeof(struct lock_log_entry *)) {
 399                 return EINVAL;
 400         }
 401
 402         *entry = talloc_get_type_abort(*(void **)databuf,
 403                                        struct lock_log_entry);
 404         return 0;
 405 }
 406
 407 static void lock_log_cleanup(struct tevent_context *ev,
 408                              struct tevent_timer *ttimer,
 409                              struct timeval current_time,
 410                              void *private_data)
 411 {
 412         struct lock_log_entry *entry = talloc_get_type_abort(
 413                 private_data, struct lock_log_entry);
 414         int ret;
 415
 416         entry->timer = NULL;
 417
 418         ret = db_hash_delete(entry->lock_log, entry->key.dptr,
 419                              entry->key.dsize);
 420         if (ret != 0) {
 421                 return;
 422         }
 423         talloc_free(entry);
 424 }
 425
 426 static bool lock_log_skip(struct tevent_context *ev,
 427                           struct db_hash_context *lock_log,
 428                           TDB_DATA key, unsigned long elapsed_sec)
 429 {
 430         struct lock_log_entry *entry = NULL;
 431         int ret;
 432
 433         ret = db_hash_fetch(lock_log, key.dptr, key.dsize,
 434                             lock_log_fetch_parser, &entry);
 435         if (ret == ENOENT) {
 436
 437                 entry = talloc_zero(lock_log, struct lock_log_entry);
 438                 if (entry == NULL) {
 439                         goto fail;
 440                 }
 441
 442                 entry->lock_log = lock_log;
 443
 444                 entry->key.dptr = talloc_memdup(entry, key.dptr, key.dsize);
 445                 if (entry->key.dptr == NULL) {
 446                         talloc_free(entry);
 447                         goto fail;
 448                 }
 449                 entry->key.dsize = key.dsize;
 450
 451                 entry->log_sec = elapsed_sec;
 452                 entry->timer = tevent_add_timer(ev, entry,
 453                                                 timeval_current_ofs(30, 0),
 454                                                 lock_log_cleanup, entry);
 455                 if (entry->timer == NULL) {
 456                         talloc_free(entry);
 457                         goto fail;
 458                 }
 459
 460                 ret = db_hash_add(lock_log, key.dptr, key.dsize,
 461                                   (uint8_t *)&entry,
 462                                   sizeof(struct lock_log_entry *));
 463                 if (ret != 0) {
 464                         talloc_free(entry);
 465                         goto fail;
 466                 }
 467
 468                 return false;
 469
 470         } else if (ret == EINVAL) {
 471
 472                 ret = db_hash_delete(lock_log, key.dptr, key.dsize);
 473                 if (ret != 0) {
 474                         goto fail;
 475                 }
 476
 477                 return false;
 478
 479         } else if (ret == 0) {
 480
 481                 if (elapsed_sec <= entry->log_sec) {
 482                         return true;
 483                 }
 484
 485                 entry->log_sec = elapsed_sec;
 486
 487                 TALLOC_FREE(entry->timer);
 488                 entry->timer = tevent_add_timer(ev, entry,
 489                                                 timeval_current_ofs(30, 0),
 490                                                 lock_log_cleanup, entry);
 491                 if (entry->timer == NULL) {
 492                         ret = db_hash_delete(lock_log, key.dptr, key.dsize);
 493                         if (ret != 0) {
 494                                 goto fail;
 495                         }
 496                         talloc_free(entry);
 497                 }
 498
 499                 return false;
 500         }
 501
 502
 503 fail:
 504         return false;
 505
 506 }
 507
 508 /*
 509  * Callback routine when required locks are not obtained within timeout
 510  * Called from parent context
 511  */
 512 static void ctdb_lock_timeout_handler(struct tevent_context *ev,
 513                                     struct tevent_timer *ttimer,
 514                                     struct timeval current_time,
 515                                     void *private_data)
 516 {
 517         static char debug_locks[PATH_MAX+1] = "";
 518         struct lock_context *lock_ctx;
 519         struct ctdb_context *ctdb;
 520         pid_t pid;
 521         double elapsed_time;
 522         bool skip;
 523         char *keystr;
 524
 525         lock_ctx = talloc_get_type_abort(private_data, struct lock_context);
 526         ctdb = lock_ctx->ctdb;
 527
 528         elapsed_time = timeval_elapsed(&lock_ctx->start_time);
 529
 530         /* For database locks, always log */
 531         if (lock_ctx->type == LOCK_DB) {
 532                 DEBUG(DEBUG_WARNING,
 533                       ("Unable to get DB lock on database %s for "
 534                        "%.0lf seconds\n",
 535                        lock_ctx->ctdb_db->db_name, elapsed_time));
 536                 goto lock_debug;
 537         }
 538
 539         /* For record locks, check if we have already logged */
 540         skip = lock_log_skip(ev, lock_ctx->ctdb_db->lock_log,
 541                              lock_ctx->key, (unsigned long)elapsed_time);
 542         if (skip) {
 543                 goto skip_lock_debug;
 544         }
 545
 546         keystr = hex_encode_talloc(lock_ctx, lock_ctx->key.dptr,
 547                                    lock_ctx->key.dsize);
 548         DEBUG(DEBUG_WARNING,
 549               ("Unable to get RECORD lock on database %s for %.0lf seconds"
 550                " (key %s)\n",
 551                lock_ctx->ctdb_db->db_name, elapsed_time,
 552                keystr ? keystr : ""));
 553         TALLOC_FREE(keystr);
 554
 555         /* If a node stopped/banned, don't spam the logs */
 556         if (ctdb->nodes[ctdb->pnn]->flags & NODE_FLAGS_INACTIVE) {
 557                 goto skip_lock_debug;
 558         }
 559
 560 lock_debug:
 561
 562         if (ctdb_set_helper("lock debugging helper",
 563                             debug_locks, sizeof(debug_locks),
 564                             "CTDB_DEBUG_LOCKS",
 565                             getenv("CTDB_BASE"), "debug_locks.sh")) {
 566                 pid = vfork();
 567                 if (pid == 0) {
 568                         execl(debug_locks, debug_locks, NULL);
 569                         _exit(0);
 570                 }
 571                 ctdb_track_child(ctdb, pid);
 572         } else {
 573                 DEBUG(DEBUG_WARNING,
 574                       (__location__
 575                        " Unable to setup lock debugging\n"));
 576         }
 577
 578 skip_lock_debug:
 579
 580         /* reset the timeout timer */
 581         // talloc_free(lock_ctx->ttimer);
 582         lock_ctx->ttimer = tevent_add_timer(ctdb->ev,
 583                                             lock_ctx,
 584                                             timeval_current_ofs(10, 0),
 585                                             ctdb_lock_timeout_handler,
 586                                             (void *)lock_ctx);
 587 }
 588
 589 static bool lock_helper_args(TALLOC_CTX *mem_ctx,
 590                              struct lock_context *lock_ctx, int fd,
 591                              int *argc, const char ***argv)
 592 {
 593         const char **args = NULL;
 594         int nargs = 0, i;
 595
 596         switch (lock_ctx->type) {
 597         case LOCK_RECORD:
 598                 nargs = 6;
 599                 break;
 600
 601         case LOCK_DB:
 602                 nargs = 5;
 603                 break;
 604         }
 605
 606         /* Add extra argument for null termination */
 607         nargs++;
 608
 609         args = talloc_array(mem_ctx, const char *, nargs);
 610         if (args == NULL) {
 611                 return false;
 612         }
 613
 614         args[0] = talloc_asprintf(args, "%d", getpid());
 615         args[1] = talloc_asprintf(args, "%d", fd);
 616
 617         switch (lock_ctx->type) {
 618         case LOCK_RECORD:
 619                 args[2] = talloc_strdup(args, "RECORD");
 620                 args[3] = talloc_strdup(args, lock_ctx->ctdb_db->db_path);
 621                 args[4] = talloc_asprintf(args, "0x%x",
 622                                 tdb_get_flags(lock_ctx->ctdb_db->ltdb->tdb));
 623                 if (lock_ctx->key.dsize == 0) {
 624                         args[5] = talloc_strdup(args, "NULL");
 625                 } else {
 626                         args[5] = hex_encode_talloc(args, lock_ctx->key.dptr, lock_ctx->key.dsize);
 627                 }
 628                 break;
 629
 630         case LOCK_DB:
 631                 args[2] = talloc_strdup(args, "DB");
 632                 args[3] = talloc_strdup(args, lock_ctx->ctdb_db->db_path);
 633                 args[4] = talloc_asprintf(args, "0x%x",
 634                                 tdb_get_flags(lock_ctx->ctdb_db->ltdb->tdb));
 635                 break;
 636         }
 637
 638         /* Make sure last argument is NULL */
 639         args[nargs-1] = NULL;
 640
 641         for (i=0; i<nargs-1; i++) {
 642                 if (args[i] == NULL) {
 643                         talloc_free(args);
 644                         return false;
 645                 }
 646         }
 647
 648         *argc = nargs;
 649         *argv = args;
 650         return true;
 651 }
 652
 653 /*
 654  * Find a lock request that can be scheduled
 655  */
 656 static struct lock_context *ctdb_find_lock_context(struct ctdb_context *ctdb)
 657 {
 658         struct lock_context *lock_ctx, *next_ctx;
 659         struct ctdb_db_context *ctdb_db;
 660
 661         /* First check if there are database lock requests */
 662
 663         for (lock_ctx = ctdb->lock_pending; lock_ctx != NULL;
 664              lock_ctx = next_ctx) {
 665
 666                 if (lock_ctx->request != NULL) {
 667                         /* Found a lock context with a request */
 668                         return lock_ctx;
 669                 }
 670
 671                 next_ctx = lock_ctx->next;
 672
 673                 DEBUG(DEBUG_INFO, ("Removing lock context without lock "
 674                                    "request\n"));
 675                 DLIST_REMOVE(ctdb->lock_pending, lock_ctx);
 676                 CTDB_DECREMENT_STAT(ctdb, locks.num_pending);
 677                 if (lock_ctx->ctdb_db) {
 678                         CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db,
 679                                                locks.num_pending);
 680                 }
 681                 talloc_free(lock_ctx);
 682         }
 683
 684         /* Next check database queues */
 685         for (ctdb_db = ctdb->db_list; ctdb_db; ctdb_db = ctdb_db->next) {
 686                 if (ctdb_db->lock_num_current ==
 687                     ctdb->tunable.lock_processes_per_db) {
 688                         continue;
 689                 }
 690
 691                 for (lock_ctx = ctdb_db->lock_pending; lock_ctx != NULL;
 692                      lock_ctx = next_ctx) {
 693
 694                         next_ctx = lock_ctx->next;
 695
 696                         if (lock_ctx->request != NULL) {
 697                                 return lock_ctx;
 698                         }
 699
 700                         DEBUG(DEBUG_INFO, ("Removing lock context without "
 701                                            "lock request\n"));
 702                         DLIST_REMOVE(ctdb_db->lock_pending, lock_ctx);
 703                         CTDB_DECREMENT_STAT(ctdb, locks.num_pending);
 704                         CTDB_DECREMENT_DB_STAT(ctdb_db, locks.num_pending);
 705                         talloc_free(lock_ctx);
 706                 }
 707         }
 708
 709         return NULL;
 710 }
 711
 712 /*
 713  * Schedule a new lock child process
 714  * Set up callback handler and timeout handler
 715  */
 716 static void ctdb_lock_schedule(struct ctdb_context *ctdb)
 717 {
 718         struct lock_context *lock_ctx;
 719         int ret, argc;
 720         TALLOC_CTX *tmp_ctx;
 721         static char prog[PATH_MAX+1] = "";
 722         const char **args;
 723
 724         if (!ctdb_set_helper("lock helper",
 725                              prog, sizeof(prog),
 726                              "CTDB_LOCK_HELPER",
 727                              CTDB_HELPER_BINDIR, "ctdb_lock_helper")) {
 728                 ctdb_die(ctdb, __location__
 729                          " Unable to set lock helper\n");
 730         }
 731
 732         /* Find a lock context with requests */
 733         lock_ctx = ctdb_find_lock_context(ctdb);
 734         if (lock_ctx == NULL) {
 735                 return;
 736         }
 737
 738         lock_ctx->child = -1;
 739         ret = pipe(lock_ctx->fd);
 740         if (ret != 0) {
 741                 DEBUG(DEBUG_ERR, ("Failed to create pipe in ctdb_lock_schedule\n"));
 742                 return;
 743         }
 744
 745         set_close_on_exec(lock_ctx->fd[0]);
 746
 747         /* Create data for child process */
 748         tmp_ctx = talloc_new(lock_ctx);
 749         if (tmp_ctx == NULL) {
 750                 DEBUG(DEBUG_ERR, ("Failed to allocate memory for helper args\n"));
 751                 close(lock_ctx->fd[0]);
 752                 close(lock_ctx->fd[1]);
 753                 return;
 754         }
 755
 756         if (! ctdb->do_setsched) {
 757                 ret = setenv("CTDB_NOSETSCHED", "1", 1);
 758                 if (ret != 0) {
 759                         DEBUG(DEBUG_WARNING,
 760                               ("Failed to set CTDB_NOSETSCHED variable\n"));
 761                 }
 762         }
 763
 764         /* Create arguments for lock helper */
 765         if (!lock_helper_args(tmp_ctx, lock_ctx, lock_ctx->fd[1],
 766                               &argc, &args)) {
 767                 DEBUG(DEBUG_ERR, ("Failed to create lock helper args\n"));
 768                 close(lock_ctx->fd[0]);
 769                 close(lock_ctx->fd[1]);
 770                 talloc_free(tmp_ctx);
 771                 return;
 772         }
 773
 774         lock_ctx->child = ctdb_vfork_exec(lock_ctx, ctdb, prog, argc,
 775                                           (const char **)args);
 776         if (lock_ctx->child == -1) {
 777                 DEBUG(DEBUG_ERR, ("Failed to create a child in ctdb_lock_schedule\n"));
 778                 close(lock_ctx->fd[0]);
 779                 close(lock_ctx->fd[1]);
 780                 talloc_free(tmp_ctx);
 781                 return;
 782         }
 783
 784         /* Parent process */
 785         close(lock_ctx->fd[1]);
 786
 787         talloc_free(tmp_ctx);
 788
 789         /* Set up timeout handler */
 790         lock_ctx->ttimer = tevent_add_timer(ctdb->ev,
 791                                             lock_ctx,
 792                                             timeval_current_ofs(10, 0),
 793                                             ctdb_lock_timeout_handler,
 794                                             (void *)lock_ctx);
 795         if (lock_ctx->ttimer == NULL) {
 796                 ctdb_kill(ctdb, lock_ctx->child, SIGTERM);
 797                 lock_ctx->child = -1;
 798                 close(lock_ctx->fd[0]);
 799                 return;
 800         }
 801
 802         /* Set up callback */
 803         lock_ctx->tfd = tevent_add_fd(ctdb->ev,
 804                                       lock_ctx,
 805                                       lock_ctx->fd[0],
 806                                       TEVENT_FD_READ,
 807                                       ctdb_lock_handler,
 808                                       (void *)lock_ctx);
 809         if (lock_ctx->tfd == NULL) {
 810                 TALLOC_FREE(lock_ctx->ttimer);
 811                 ctdb_kill(ctdb, lock_ctx->child, SIGTERM);
 812                 lock_ctx->child = -1;
 813                 close(lock_ctx->fd[0]);
 814                 return;
 815         }
 816         tevent_fd_set_auto_close(lock_ctx->tfd);
 817
 818         /* Move the context from pending to current */
 819         if (lock_ctx->type == LOCK_RECORD) {
 820                 DLIST_REMOVE(lock_ctx->ctdb_db->lock_pending, lock_ctx);
 821                 DLIST_ADD_END(lock_ctx->ctdb_db->lock_current, lock_ctx);
 822         } else {
 823                 DLIST_REMOVE(ctdb->lock_pending, lock_ctx);
 824                 DLIST_ADD_END(ctdb->lock_current, lock_ctx);
 825         }
 826         CTDB_DECREMENT_STAT(lock_ctx->ctdb, locks.num_pending);
 827         CTDB_INCREMENT_STAT(lock_ctx->ctdb, locks.num_current);
 828         if (lock_ctx->ctdb_db) {
 829                 lock_ctx->ctdb_db->lock_num_current++;
 830                 CTDB_DECREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_pending);
 831                 CTDB_INCREMENT_DB_STAT(lock_ctx->ctdb_db, locks.num_current);
 832         }
 833 }
 834
 835
 836 /*
 837  * Lock record / db depending on type
 838  */
 839 static struct lock_request *ctdb_lock_internal(TALLOC_CTX *mem_ctx,
 840                                                struct ctdb_context *ctdb,
 841                                                struct ctdb_db_context *ctdb_db,
 842                                                TDB_DATA key,
 843                                                uint32_t priority,
 844                                                void (*callback)(void *, bool),
 845                                                void *private_data,
 846                                                enum lock_type type,
 847                                                bool auto_mark)
 848 {
 849         struct lock_context *lock_ctx = NULL;
 850         struct lock_request *request;
 851
 852         if (callback == NULL) {
 853                 DEBUG(DEBUG_WARNING, ("No callback function specified, not locking\n"));
 854                 return NULL;
 855         }
 856
 857         lock_ctx = talloc_zero(ctdb, struct lock_context);
 858         if (lock_ctx == NULL) {
 859                 DEBUG(DEBUG_ERR, ("Failed to create a new lock context\n"));
 860                 return NULL;
 861         }
 862
 863         if ((request = talloc_zero(mem_ctx, struct lock_request)) == NULL) {
 864                 talloc_free(lock_ctx);
 865                 return NULL;
 866         }
 867
 868         lock_ctx->type = type;
 869         lock_ctx->ctdb = ctdb;
 870         lock_ctx->ctdb_db = ctdb_db;
 871         lock_ctx->key.dsize = key.dsize;
 872         if (key.dsize > 0) {
 873                 lock_ctx->key.dptr = talloc_memdup(lock_ctx, key.dptr, key.dsize);
 874                 if (lock_ctx->key.dptr == NULL) {
 875                         DEBUG(DEBUG_ERR, (__location__ "Memory allocation error\n"));
 876                         talloc_free(lock_ctx);
 877                         talloc_free(request);
 878                         return NULL;
 879                 }
 880                 lock_ctx->key_hash = ctdb_hash(&key);
 881         } else {
 882                 lock_ctx->key.dptr = NULL;
 883         }
 884         lock_ctx->priority = priority;
 885         lock_ctx->auto_mark = auto_mark;
 886
 887         lock_ctx->request = request;
 888         lock_ctx->child = -1;
 889
 890         /* Non-record locks are required by recovery and should be scheduled
 891          * immediately, so keep them at the head of the pending queue.
 892          */
 893         if (lock_ctx->type == LOCK_RECORD) {
 894                 DLIST_ADD_END(ctdb_db->lock_pending, lock_ctx);
 895         } else {
 896                 DLIST_ADD_END(ctdb->lock_pending, lock_ctx);
 897         }
 898         CTDB_INCREMENT_STAT(ctdb, locks.num_pending);
 899         if (ctdb_db) {
 900                 CTDB_INCREMENT_DB_STAT(ctdb_db, locks.num_pending);
 901         }
 902
 903         /* Start the timer when we activate the context */
 904         lock_ctx->start_time = timeval_current();
 905
 906         request->lctx = lock_ctx;
 907         request->callback = callback;
 908         request->private_data = private_data;
 909
 910         talloc_set_destructor(request, ctdb_lock_request_destructor);
 911         talloc_set_destructor(lock_ctx, ctdb_lock_context_destructor);
 912
 913         ctdb_lock_schedule(ctdb);
 914
 915         return request;
 916 }
 917
 918
 919 /*
 920  * obtain a lock on a record in a database
 921  */
 922 struct lock_request *ctdb_lock_record(TALLOC_CTX *mem_ctx,
 923                                       struct ctdb_db_context *ctdb_db,
 924                                       TDB_DATA key,
 925                                       bool auto_mark,
 926                                       void (*callback)(void *, bool),
 927                                       void *private_data)
 928 {
 929         return ctdb_lock_internal(mem_ctx,
 930                                   ctdb_db->ctdb,
 931                                   ctdb_db,
 932                                   key,
 933                                   0,
 934                                   callback,
 935                                   private_data,
 936                                   LOCK_RECORD,
 937                                   auto_mark);
 938 }
 939
 940
 941 /*
 942  * obtain a lock on a database
 943  */
 944 struct lock_request *ctdb_lock_db(TALLOC_CTX *mem_ctx,
 945                                   struct ctdb_db_context *ctdb_db,
 946                                   bool auto_mark,
 947                                   void (*callback)(void *, bool),
 948                                   void *private_data)
 949 {
 950         return ctdb_lock_internal(mem_ctx,
 951                                   ctdb_db->ctdb,
 952                                   ctdb_db,
 953                                   tdb_null,
 954                                   0,
 955                                   callback,
 956                                   private_data,
 957                                   LOCK_DB,
 958                                   auto_mark);
 959 }