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