src/core/transaction.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <fcntl.h>
   4 #include <unistd.h>
   5
   6 #include "alloc-util.h"
   7 #include "bus-common-errors.h"
   8 #include "bus-error.h"
   9 #include "dbus-unit.h"
  10 #include "strv.h"
  11 #include "terminal-util.h"
  12 #include "transaction.h"
  13
  14 static void transaction_unlink_job(Transaction *tr, Job *j, bool delete_dependencies);
  15
  16 static void transaction_delete_job(Transaction *tr, Job *j, bool delete_dependencies) {
  17         assert(tr);
  18         assert(j);
  19
  20         /* Deletes one job from the transaction */
  21
  22         transaction_unlink_job(tr, j, delete_dependencies);
  23
  24         job_free(j);
  25 }
  26
  27 static void transaction_delete_unit(Transaction *tr, Unit *u) {
  28         Job *j;
  29
  30         /* Deletes all jobs associated with a certain unit from the
  31          * transaction */
  32
  33         while ((j = hashmap_get(tr->jobs, u)))
  34                 transaction_delete_job(tr, j, true);
  35 }
  36
  37 void transaction_abort(Transaction *tr) {
  38         Job *j;
  39
  40         assert(tr);
  41
  42         while ((j = hashmap_first(tr->jobs)))
  43                 transaction_delete_job(tr, j, false);
  44
  45         assert(hashmap_isempty(tr->jobs));
  46 }
  47
  48 static void transaction_find_jobs_that_matter_to_anchor(Job *j, unsigned generation) {
  49         assert(j);
  50
  51         /* A recursive sweep through the graph that marks all units
  52          * that matter to the anchor job, i.e. are directly or
  53          * indirectly a dependency of the anchor job via paths that
  54          * are fully marked as mattering. */
  55
  56         j->matters_to_anchor = true;
  57         j->generation = generation;
  58
  59         LIST_FOREACH(subject, l, j->subject_list) {
  60
  61                 /* This link does not matter */
  62                 if (!l->matters)
  63                         continue;
  64
  65                 /* This unit has already been marked */
  66                 if (l->object->generation == generation)
  67                         continue;
  68
  69                 transaction_find_jobs_that_matter_to_anchor(l->object, generation);
  70         }
  71 }
  72
  73 static void transaction_merge_and_delete_job(Transaction *tr, Job *j, Job *other, JobType t) {
  74         JobDependency *last;
  75
  76         assert(j);
  77         assert(other);
  78         assert(j->unit == other->unit);
  79         assert(!j->installed);
  80
  81         /* Merges 'other' into 'j' and then deletes 'other'. */
  82
  83         j->type = t;
  84         j->state = JOB_WAITING;
  85         j->irreversible = j->irreversible || other->irreversible;
  86         j->matters_to_anchor = j->matters_to_anchor || other->matters_to_anchor;
  87
  88         /* Patch us in as new owner of the JobDependency objects */
  89         last = NULL;
  90         LIST_FOREACH(subject, l, other->subject_list) {
  91                 assert(l->subject == other);
  92                 l->subject = j;
  93                 last = l;
  94         }
  95
  96         /* Merge both lists */
  97         if (last) {
  98                 last->subject_next = j->subject_list;
  99                 if (j->subject_list)
 100                         j->subject_list->subject_prev = last;
 101                 j->subject_list = other->subject_list;
 102         }
 103
 104         /* Patch us in as new owner of the JobDependency objects */
 105         last = NULL;
 106         LIST_FOREACH(object, l, other->object_list) {
 107                 assert(l->object == other);
 108                 l->object = j;
 109                 last = l;
 110         }
 111
 112         /* Merge both lists */
 113         if (last) {
 114                 last->object_next = j->object_list;
 115                 if (j->object_list)
 116                         j->object_list->object_prev = last;
 117                 j->object_list = other->object_list;
 118         }
 119
 120         /* Kill the other job */
 121         other->subject_list = NULL;
 122         other->object_list = NULL;
 123         transaction_delete_job(tr, other, true);
 124 }
 125
 126 _pure_ static bool job_is_conflicted_by(Job *j) {
 127         assert(j);
 128
 129         /* Returns true if this job is pulled in by a least one
 130          * ConflictedBy dependency. */
 131
 132         LIST_FOREACH(object, l, j->object_list)
 133                 if (l->conflicts)
 134                         return true;
 135
 136         return false;
 137 }
 138
 139 static int delete_one_unmergeable_job(Transaction *tr, Job *job) {
 140         assert(job);
 141
 142         /* Tries to delete one item in the linked list
 143          * j->transaction_next->transaction_next->... that conflicts
 144          * with another one, in an attempt to make an inconsistent
 145          * transaction work. */
 146
 147         /* We rely here on the fact that if a merged with b does not
 148          * merge with c, either a or b merge with c neither */
 149         LIST_FOREACH(transaction, j, job)
 150                 LIST_FOREACH(transaction, k, j->transaction_next) {
 151                         Job *d;
 152
 153                         /* Is this one mergeable? Then skip it */
 154                         if (job_type_is_mergeable(j->type, k->type))
 155                                 continue;
 156
 157                         /* Ok, we found two that conflict, let's see if we can
 158                          * drop one of them */
 159                         if (!j->matters_to_anchor && !k->matters_to_anchor) {
 160
 161                                 /* Both jobs don't matter, so let's
 162                                  * find the one that is smarter to
 163                                  * remove. Let's think positive and
 164                                  * rather remove stops then starts --
 165                                  * except if something is being
 166                                  * stopped because it is conflicted by
 167                                  * another unit in which case we
 168                                  * rather remove the start. */
 169
 170                                 log_unit_debug(j->unit,
 171                                                "Looking at job %s/%s conflicted_by=%s",
 172                                                j->unit->id, job_type_to_string(j->type),
 173                                                yes_no(j->type == JOB_STOP && job_is_conflicted_by(j)));
 174                                 log_unit_debug(k->unit,
 175                                                "Looking at job %s/%s conflicted_by=%s",
 176                                                k->unit->id, job_type_to_string(k->type),
 177                                                yes_no(k->type == JOB_STOP && job_is_conflicted_by(k)));
 178
 179                                 if (j->type == JOB_STOP) {
 180
 181                                         if (job_is_conflicted_by(j))
 182                                                 d = k;
 183                                         else
 184                                                 d = j;
 185
 186                                 } else if (k->type == JOB_STOP) {
 187
 188                                         if (job_is_conflicted_by(k))
 189                                                 d = j;
 190                                         else
 191                                                 d = k;
 192                                 } else
 193                                         d = j;
 194
 195                         } else if (!j->matters_to_anchor)
 196                                 d = j;
 197                         else if (!k->matters_to_anchor)
 198                                 d = k;
 199                         else
 200                                 return -ENOEXEC;
 201
 202                         /* Ok, we can drop one, so let's do so. */
 203                         log_unit_debug(d->unit,
 204                                        "Fixing conflicting jobs %s/%s,%s/%s by deleting job %s/%s",
 205                                        j->unit->id, job_type_to_string(j->type),
 206                                        k->unit->id, job_type_to_string(k->type),
 207                                        d->unit->id, job_type_to_string(d->type));
 208                         transaction_delete_job(tr, d, true);
 209                         return 0;
 210                 }
 211
 212         return -EINVAL;
 213 }
 214
 215 static int transaction_merge_jobs(Transaction *tr, sd_bus_error *e) {
 216         Job *j;
 217         int r;
 218
 219         assert(tr);
 220
 221         /* First step, check whether any of the jobs for one specific
 222          * task conflict. If so, try to drop one of them. */
 223         HASHMAP_FOREACH(j, tr->jobs) {
 224                 JobType t;
 225
 226                 t = j->type;
 227                 LIST_FOREACH(transaction, k, j->transaction_next) {
 228                         if (job_type_merge_and_collapse(&t, k->type, j->unit) >= 0)
 229                                 continue;
 230
 231                         /* OK, we could not merge all jobs for this
 232                          * action. Let's see if we can get rid of one
 233                          * of them */
 234
 235                         r = delete_one_unmergeable_job(tr, j);
 236                         if (r >= 0)
 237                                 /* Ok, we managed to drop one, now
 238                                  * let's ask our callers to call us
 239                                  * again after garbage collecting */
 240                                 return -EAGAIN;
 241
 242                         /* We couldn't merge anything. Failure */
 243                         return sd_bus_error_setf(e, BUS_ERROR_TRANSACTION_JOBS_CONFLICTING,
 244                                                  "Transaction contains conflicting jobs '%s' and '%s' for %s. "
 245                                                  "Probably contradicting requirement dependencies configured.",
 246                                                  job_type_to_string(t),
 247                                                  job_type_to_string(k->type),
 248                                                  k->unit->id);
 249                 }
 250         }
 251
 252         /* Second step, merge the jobs. */
 253         HASHMAP_FOREACH(j, tr->jobs) {
 254                 JobType t = j->type;
 255
 256                 /* Merge all transaction jobs for j->unit */
 257                 LIST_FOREACH(transaction, k, j->transaction_next)
 258                         assert_se(job_type_merge_and_collapse(&t, k->type, j->unit) == 0);
 259
 260                 Job *k;
 261                 while ((k = j->transaction_next)) {
 262                         if (tr->anchor_job == k) {
 263                                 transaction_merge_and_delete_job(tr, k, j, t);
 264                                 j = k;
 265                         } else
 266                                 transaction_merge_and_delete_job(tr, j, k, t);
 267                 }
 268
 269                 assert(!j->transaction_next);
 270                 assert(!j->transaction_prev);
 271         }
 272
 273         return 0;
 274 }
 275
 276 static void transaction_drop_redundant(Transaction *tr) {
 277         bool again;
 278
 279         /* Goes through the transaction and removes all jobs of the units whose jobs are all noops. If not
 280          * all of a unit's jobs are redundant, they are kept. */
 281
 282         assert(tr);
 283
 284         do {
 285                 Job *j;
 286
 287                 again = false;
 288
 289                 HASHMAP_FOREACH(j, tr->jobs) {
 290                         bool keep = false;
 291
 292                         LIST_FOREACH(transaction, k, j)
 293                                 if (tr->anchor_job == k ||
 294                                     !job_type_is_redundant(k->type, unit_active_state(k->unit)) ||
 295                                     (k->unit->job && job_type_is_conflicting(k->type, k->unit->job->type))) {
 296                                         keep = true;
 297                                         break;
 298                                 }
 299
 300                         if (!keep) {
 301                                 log_trace("Found redundant job %s/%s, dropping from transaction.",
 302                                           j->unit->id, job_type_to_string(j->type));
 303                                 transaction_delete_job(tr, j, false);
 304                                 again = true;
 305                                 break;
 306                         }
 307                 }
 308         } while (again);
 309 }
 310
 311 _pure_ static bool unit_matters_to_anchor(Unit *u, Job *job) {
 312         assert(u);
 313         assert(job);
 314         assert(!job->transaction_prev);
 315
 316         /* Checks whether at least one of the jobs for this unit
 317          * matters to the anchor. */
 318
 319         LIST_FOREACH(transaction, j, job)
 320                 if (j->matters_to_anchor)
 321                         return true;
 322
 323         return false;
 324 }
 325
 326 static char* merge_unit_ids(const char* unit_log_field, char **pairs) {
 327         char *ans = NULL;
 328         size_t size = 0, next;
 329
 330         STRV_FOREACH_PAIR(unit_id, job_type, pairs) {
 331                 next = strlen(unit_log_field) + strlen(*unit_id);
 332                 if (!GREEDY_REALLOC(ans, size + next + 1))
 333                         return mfree(ans);
 334
 335                 sprintf(ans + size, "%s%s", unit_log_field, *unit_id);
 336                 if (*(unit_id+1))
 337                         ans[size + next] =  '\n';
 338                 size += next + 1;
 339         }
 340
 341         return ans;
 342 }
 343
 344 static int transaction_verify_order_one(Transaction *tr, Job *j, Job *from, unsigned generation, sd_bus_error *e) {
 345
 346         static const UnitDependencyAtom directions[] = {
 347                 UNIT_ATOM_BEFORE,
 348                 UNIT_ATOM_AFTER,
 349         };
 350
 351         int r;
 352
 353         assert(tr);
 354         assert(j);
 355         assert(!j->transaction_prev);
 356
 357         /* Does a recursive sweep through the ordering graph, looking for a cycle. If we find a cycle we try
 358          * to break it. */
 359
 360         /* Have we seen this before? */
 361         if (j->generation == generation) {
 362                 Job *k, *delete = NULL;
 363                 _cleanup_free_ char **array = NULL, *unit_ids = NULL;
 364
 365                 /* If the marker is NULL we have been here already and decided the job was loop-free from
 366                  * here. Hence shortcut things and return right-away. */
 367                 if (!j->marker)
 368                         return 0;
 369
 370                 /* So, the marker is not NULL and we already have been here. We have a cycle. Let's try to
 371                  * break it. We go backwards in our path and try to find a suitable job to remove. We use the
 372                  * marker to find our way back, since smart how we are we stored our way back in there. */
 373                 for (k = from; k; k = ((k->generation == generation && k->marker != k) ? k->marker : NULL)) {
 374
 375                         /* For logging below */
 376                         if (strv_push_pair(&array, k->unit->id, (char*) job_type_to_string(k->type)) < 0)
 377                                 log_oom();
 378
 379                         if (!delete && hashmap_get(tr->jobs, k->unit) && !unit_matters_to_anchor(k->unit, k))
 380                                 /* Ok, we can drop this one, so let's do so. */
 381                                 delete = k;
 382
 383                         /* Check if this in fact was the beginning of the cycle */
 384                         if (k == j)
 385                                 break;
 386                 }
 387
 388                 unit_ids = merge_unit_ids(j->manager->unit_log_field, array); /* ignore error */
 389
 390                 STRV_FOREACH_PAIR(unit_id, job_type, array)
 391                         /* logging for j not k here to provide a consistent narrative */
 392                         log_struct(LOG_WARNING,
 393                                    LOG_UNIT_MESSAGE(j->unit,
 394                                                     "Found %s on %s/%s",
 395                                                     unit_id == array ? "ordering cycle" : "dependency",
 396                                                     *unit_id, *job_type),
 397                                    "%s", unit_ids);
 398
 399                 if (delete) {
 400                         const char *status;
 401                         /* logging for j not k here to provide a consistent narrative */
 402                         log_struct(LOG_ERR,
 403                                    LOG_UNIT_MESSAGE(j->unit,
 404                                                     "Job %s/%s deleted to break ordering cycle starting with %s/%s",
 405                                                     delete->unit->id, job_type_to_string(delete->type),
 406                                                     j->unit->id, job_type_to_string(j->type)),
 407                                    "%s", unit_ids);
 408
 409                         if (log_get_show_color())
 410                                 status = ANSI_HIGHLIGHT_RED " SKIP " ANSI_NORMAL;
 411                         else
 412                                 status = " SKIP ";
 413
 414                         unit_status_printf(delete->unit,
 415                                            STATUS_TYPE_NOTICE,
 416                                            status,
 417                                            "Ordering cycle found, skipping %s",
 418                                            unit_status_string(delete->unit, NULL));
 419                         transaction_delete_unit(tr, delete->unit);
 420                         return -EAGAIN;
 421                 }
 422
 423                 log_struct(LOG_ERR,
 424                            LOG_UNIT_MESSAGE(j->unit, "Unable to break cycle starting with %s/%s",
 425                                             j->unit->id, job_type_to_string(j->type)),
 426                            "%s", unit_ids);
 427
 428                 return sd_bus_error_setf(e, BUS_ERROR_TRANSACTION_ORDER_IS_CYCLIC,
 429                                          "Transaction order is cyclic. See system logs for details.");
 430         }
 431
 432         /* Make the marker point to where we come from, so that we can
 433          * find our way backwards if we want to break a cycle. We use
 434          * a special marker for the beginning: we point to
 435          * ourselves. */
 436         j->marker = from ? from : j;
 437         j->generation = generation;
 438
 439         /* Actual ordering of jobs depends on the unit ordering dependency and job types. We need to traverse
 440          * the graph over 'before' edges in the actual job execution order. We traverse over both unit
 441          * ordering dependencies and we test with job_compare() whether it is the 'before' edge in the job
 442          * execution ordering. */
 443         for (size_t d = 0; d < ELEMENTSOF(directions); d++) {
 444                 Unit *u;
 445
 446                 UNIT_FOREACH_DEPENDENCY(u, j->unit, directions[d]) {
 447                         Job *o;
 448
 449                         /* Is there a job for this unit? */
 450                         o = hashmap_get(tr->jobs, u);
 451                         if (!o) {
 452                                 /* Ok, there is no job for this in the transaction, but maybe there is
 453                                  * already one running? */
 454                                 o = u->job;
 455                                 if (!o)
 456                                         continue;
 457                         }
 458
 459                         /* Cut traversing if the job j is not really *before* o. */
 460                         if (job_compare(j, o, directions[d]) >= 0)
 461                                 continue;
 462
 463                         r = transaction_verify_order_one(tr, o, j, generation, e);
 464                         if (r < 0)
 465                                 return r;
 466                 }
 467         }
 468
 469         /* Ok, let's backtrack, and remember that this entry is not on
 470          * our path anymore. */
 471         j->marker = NULL;
 472
 473         return 0;
 474 }
 475
 476 static int transaction_verify_order(Transaction *tr, unsigned *generation, sd_bus_error *e) {
 477         Job *j;
 478         int r;
 479         unsigned g;
 480
 481         assert(tr);
 482         assert(generation);
 483
 484         /* Check if the ordering graph is cyclic. If it is, try to fix
 485          * that up by dropping one of the jobs. */
 486
 487         g = (*generation)++;
 488
 489         HASHMAP_FOREACH(j, tr->jobs) {
 490                 r = transaction_verify_order_one(tr, j, NULL, g, e);
 491                 if (r < 0)
 492                         return r;
 493         }
 494
 495         return 0;
 496 }
 497
 498 static void transaction_collect_garbage(Transaction *tr) {
 499         bool again;
 500
 501         assert(tr);
 502
 503         /* Drop jobs that are not required by any other job */
 504
 505         do {
 506                 Job *j;
 507
 508                 again = false;
 509
 510                 HASHMAP_FOREACH(j, tr->jobs) {
 511                         if (tr->anchor_job == j)
 512                                 continue;
 513
 514                         if (!j->object_list) {
 515                                 log_trace("Garbage collecting job %s/%s", j->unit->id, job_type_to_string(j->type));
 516                                 transaction_delete_job(tr, j, true);
 517                                 again = true;
 518                                 break;
 519                         }
 520
 521                         log_trace("Keeping job %s/%s because of %s/%s",
 522                                   j->unit->id, job_type_to_string(j->type),
 523                                   j->object_list->subject ? j->object_list->subject->unit->id : "root",
 524                                   j->object_list->subject ? job_type_to_string(j->object_list->subject->type) : "root");
 525                 }
 526
 527         } while (again);
 528 }
 529
 530 static int transaction_is_destructive(Transaction *tr, JobMode mode, sd_bus_error *e) {
 531         Job *j;
 532
 533         assert(tr);
 534
 535         /* Checks whether applying this transaction means that
 536          * existing jobs would be replaced */
 537
 538         HASHMAP_FOREACH(j, tr->jobs) {
 539
 540                 /* Assume merged */
 541                 assert(!j->transaction_prev);
 542                 assert(!j->transaction_next);
 543
 544                 if (j->unit->job && (mode == JOB_FAIL || j->unit->job->irreversible) &&
 545                     job_type_is_conflicting(j->unit->job->type, j->type))
 546                         return sd_bus_error_setf(e, BUS_ERROR_TRANSACTION_IS_DESTRUCTIVE,
 547                                                  "Transaction for %s/%s is destructive (%s has '%s' job queued, but '%s' is included in transaction).",
 548                                                  tr->anchor_job->unit->id, job_type_to_string(tr->anchor_job->type),
 549                                                  j->unit->id, job_type_to_string(j->unit->job->type), job_type_to_string(j->type));
 550         }
 551
 552         return 0;
 553 }
 554
 555 static void transaction_minimize_impact(Transaction *tr) {
 556         Job *head;
 557
 558         assert(tr);
 559
 560         /* Drops all unnecessary jobs that reverse already active jobs
 561          * or that stop a running service. */
 562
 563 rescan:
 564         HASHMAP_FOREACH(head, tr->jobs) {
 565                 LIST_FOREACH(transaction, j, head) {
 566                         bool stops_running_service, changes_existing_job;
 567
 568                         /* If it matters, we shouldn't drop it */
 569                         if (j->matters_to_anchor)
 570                                 continue;
 571
 572                         /* Would this stop a running service?
 573                          * Would this change an existing job?
 574                          * If so, let's drop this entry */
 575
 576                         stops_running_service =
 577                                 j->type == JOB_STOP && UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(j->unit));
 578
 579                         changes_existing_job =
 580                                 j->unit->job &&
 581                                 job_type_is_conflicting(j->type, j->unit->job->type);
 582
 583                         if (!stops_running_service && !changes_existing_job)
 584                                 continue;
 585
 586                         if (stops_running_service)
 587                                 log_unit_debug(j->unit,
 588                                                "%s/%s would stop a running service.",
 589                                                j->unit->id, job_type_to_string(j->type));
 590
 591                         if (changes_existing_job)
 592                                 log_unit_debug(j->unit,
 593                                                "%s/%s would change existing job.",
 594                                                j->unit->id, job_type_to_string(j->type));
 595
 596                         /* Ok, let's get rid of this */
 597                         log_unit_debug(j->unit,
 598                                        "Deleting %s/%s to minimize impact.",
 599                                        j->unit->id, job_type_to_string(j->type));
 600
 601                         transaction_delete_job(tr, j, true);
 602                         goto rescan;
 603                 }
 604         }
 605 }
 606
 607 static int transaction_apply(
 608                 Transaction *tr,
 609                 Manager *m,
 610                 JobMode mode,
 611                 Set *affected_jobs) {
 612
 613         Job *j;
 614         int r;
 615
 616         /* Moves the transaction jobs to the set of active jobs */
 617
 618         if (IN_SET(mode, JOB_ISOLATE, JOB_FLUSH)) {
 619
 620                 /* When isolating first kill all installed jobs which
 621                  * aren't part of the new transaction */
 622                 HASHMAP_FOREACH(j, m->jobs) {
 623                         assert(j->installed);
 624
 625                         if (j->unit->ignore_on_isolate)
 626                                 continue;
 627
 628                         if (hashmap_get(tr->jobs, j->unit))
 629                                 continue;
 630
 631                         /* Not invalidating recursively. Avoids triggering
 632                          * OnFailure= actions of dependent jobs. Also avoids
 633                          * invalidating our iterator. */
 634                         job_finish_and_invalidate(j, JOB_CANCELED, false, false);
 635                 }
 636         }
 637
 638         HASHMAP_FOREACH(j, tr->jobs) {
 639                 /* Assume merged */
 640                 assert(!j->transaction_prev);
 641                 assert(!j->transaction_next);
 642
 643                 r = hashmap_ensure_put(&m->jobs, NULL, UINT32_TO_PTR(j->id), j);
 644                 if (r < 0)
 645                         goto rollback;
 646         }
 647
 648         while ((j = hashmap_steal_first(tr->jobs))) {
 649                 Job *installed_job;
 650
 651                 /* Clean the job dependencies */
 652                 transaction_unlink_job(tr, j, false);
 653
 654                 installed_job = job_install(j);
 655                 if (installed_job != j) {
 656                         /* j has been merged into a previously installed job */
 657                         if (tr->anchor_job == j)
 658                                 tr->anchor_job = installed_job;
 659                         hashmap_remove(m->jobs, UINT32_TO_PTR(j->id));
 660                         job_free(j);
 661                         j = installed_job;
 662                 }
 663
 664                 job_add_to_run_queue(j);
 665                 job_add_to_dbus_queue(j);
 666                 job_start_timer(j, false);
 667                 job_shutdown_magic(j);
 668
 669                 /* When 'affected' is specified, let's track all in it all jobs that were touched because of
 670                  * this transaction. */
 671                 if (affected_jobs)
 672                         (void) set_put(affected_jobs, j);
 673         }
 674
 675         return 0;
 676
 677 rollback:
 678
 679         HASHMAP_FOREACH(j, tr->jobs)
 680                 hashmap_remove(m->jobs, UINT32_TO_PTR(j->id));
 681
 682         return r;
 683 }
 684
 685 int transaction_activate(
 686                 Transaction *tr,
 687                 Manager *m,
 688                 JobMode mode,
 689                 Set *affected_jobs,
 690                 sd_bus_error *e) {
 691
 692         Job *j;
 693         int r;
 694         unsigned generation = 1;
 695
 696         assert(tr);
 697
 698         /* This applies the changes recorded in tr->jobs to
 699          * the actual list of jobs, if possible. */
 700
 701         /* Reset the generation counter of all installed jobs. The detection of cycles
 702          * looks at installed jobs. If they had a non-zero generation from some previous
 703          * walk of the graph, the algorithm would break. */
 704         HASHMAP_FOREACH(j, m->jobs)
 705                 j->generation = 0;
 706
 707         /* First step: figure out which jobs matter */
 708         transaction_find_jobs_that_matter_to_anchor(tr->anchor_job, generation++);
 709
 710         /* Second step: Try not to stop any running services if
 711          * we don't have to. Don't try to reverse running
 712          * jobs if we don't have to. */
 713         if (mode == JOB_FAIL)
 714                 transaction_minimize_impact(tr);
 715
 716         /* Third step: Drop redundant jobs */
 717         transaction_drop_redundant(tr);
 718
 719         for (;;) {
 720                 /* Fourth step: Let's remove unneeded jobs that might
 721                  * be lurking. */
 722                 if (mode != JOB_ISOLATE)
 723                         transaction_collect_garbage(tr);
 724
 725                 /* Fifth step: verify order makes sense and correct
 726                  * cycles if necessary and possible */
 727                 r = transaction_verify_order(tr, &generation, e);
 728                 if (r >= 0)
 729                         break;
 730
 731                 if (r != -EAGAIN)
 732                         return log_warning_errno(r, "Requested transaction contains an unfixable cyclic ordering dependency: %s", bus_error_message(e, r));
 733
 734                 /* Let's see if the resulting transaction ordering
 735                  * graph is still cyclic... */
 736         }
 737
 738         for (;;) {
 739                 /* Sixth step: let's drop unmergeable entries if
 740                  * necessary and possible, merge entries we can
 741                  * merge */
 742                 r = transaction_merge_jobs(tr, e);
 743                 if (r >= 0)
 744                         break;
 745
 746                 if (r != -EAGAIN)
 747                         return log_warning_errno(r, "Requested transaction contains unmergeable jobs: %s", bus_error_message(e, r));
 748
 749                 /* Seventh step: an entry got dropped, let's garbage
 750                  * collect its dependencies. */
 751                 if (mode != JOB_ISOLATE)
 752                         transaction_collect_garbage(tr);
 753
 754                 /* Let's see if the resulting transaction still has
 755                  * unmergeable entries ... */
 756         }
 757
 758         /* Eights step: Drop redundant jobs again, if the merging now allows us to drop more. */
 759         transaction_drop_redundant(tr);
 760
 761         /* Ninth step: check whether we can actually apply this */
 762         r = transaction_is_destructive(tr, mode, e);
 763         if (r < 0)
 764                 return log_notice_errno(r, "Requested transaction contradicts existing jobs: %s", bus_error_message(e, r));
 765
 766         /* Tenth step: apply changes */
 767         r = transaction_apply(tr, m, mode, affected_jobs);
 768         if (r < 0)
 769                 return log_warning_errno(r, "Failed to apply transaction: %m");
 770
 771         assert(hashmap_isempty(tr->jobs));
 772
 773         if (!hashmap_isempty(m->jobs)) {
 774                 /* Are there any jobs now? Then make sure we have the
 775                  * idle pipe around. We don't really care too much
 776                  * whether this works or not, as the idle pipe is a
 777                  * feature for cosmetics, not actually useful for
 778                  * anything beyond that. */
 779
 780                 if (m->idle_pipe[0] < 0 && m->idle_pipe[1] < 0 &&
 781                     m->idle_pipe[2] < 0 && m->idle_pipe[3] < 0) {
 782                         (void) pipe2(m->idle_pipe, O_NONBLOCK|O_CLOEXEC);
 783                         (void) pipe2(m->idle_pipe + 2, O_NONBLOCK|O_CLOEXEC);
 784                 }
 785         }
 786
 787         return 0;
 788 }
 789
 790 static Job* transaction_add_one_job(Transaction *tr, JobType type, Unit *unit, bool *is_new) {
 791         Job *j, *f;
 792
 793         assert(tr);
 794         assert(unit);
 795
 796         /* Looks for an existing prospective job and returns that. If
 797          * it doesn't exist it is created and added to the prospective
 798          * jobs list. */
 799
 800         f = hashmap_get(tr->jobs, unit);
 801
 802         LIST_FOREACH(transaction, i, f) {
 803                 assert(i->unit == unit);
 804
 805                 if (i->type == type) {
 806                         if (is_new)
 807                                 *is_new = false;
 808                         return i;
 809                 }
 810         }
 811
 812         j = job_new(unit, type);
 813         if (!j)
 814                 return NULL;
 815
 816         j->generation = 0;
 817         j->marker = NULL;
 818         j->matters_to_anchor = false;
 819         j->irreversible = tr->irreversible;
 820
 821         LIST_PREPEND(transaction, f, j);
 822
 823         if (hashmap_replace(tr->jobs, unit, f) < 0) {
 824                 LIST_REMOVE(transaction, f, j);
 825                 job_free(j);
 826                 return NULL;
 827         }
 828
 829         if (is_new)
 830                 *is_new = true;
 831
 832         log_trace("Added job %s/%s to transaction.", unit->id, job_type_to_string(type));
 833
 834         return j;
 835 }
 836
 837 static void transaction_unlink_job(Transaction *tr, Job *j, bool delete_dependencies) {
 838         assert(tr);
 839         assert(j);
 840
 841         if (j->transaction_prev)
 842                 j->transaction_prev->transaction_next = j->transaction_next;
 843         else if (j->transaction_next)
 844                 hashmap_replace(tr->jobs, j->unit, j->transaction_next);
 845         else
 846                 hashmap_remove_value(tr->jobs, j->unit, j);
 847
 848         if (j->transaction_next)
 849                 j->transaction_next->transaction_prev = j->transaction_prev;
 850
 851         j->transaction_prev = j->transaction_next = NULL;
 852
 853         while (j->subject_list)
 854                 job_dependency_free(j->subject_list);
 855
 856         while (j->object_list) {
 857                 Job *other = j->object_list->matters ? j->object_list->subject : NULL;
 858
 859                 job_dependency_free(j->object_list);
 860
 861                 if (other && delete_dependencies) {
 862                         log_unit_debug(other->unit,
 863                                        "Deleting job %s/%s as dependency of job %s/%s",
 864                                        other->unit->id, job_type_to_string(other->type),
 865                                        j->unit->id, job_type_to_string(j->type));
 866                         transaction_delete_job(tr, other, delete_dependencies);
 867                 }
 868         }
 869 }
 870
 871 void transaction_add_propagate_reload_jobs(Transaction *tr, Unit *unit, Job *by, bool ignore_order, sd_bus_error *e) {
 872         JobType nt;
 873         Unit *dep;
 874         int r;
 875
 876         assert(tr);
 877         assert(unit);
 878
 879         UNIT_FOREACH_DEPENDENCY(dep, unit, UNIT_ATOM_PROPAGATES_RELOAD_TO) {
 880                 nt = job_type_collapse(JOB_TRY_RELOAD, dep);
 881                 if (nt == JOB_NOP)
 882                         continue;
 883
 884                 r = transaction_add_job_and_dependencies(tr, nt, dep, by, false, false, false, ignore_order, e);
 885                 if (r < 0) {
 886                         log_unit_warning(dep,
 887                                          "Cannot add dependency reload job, ignoring: %s",
 888                                          bus_error_message(e, r));
 889                         sd_bus_error_free(e);
 890                 }
 891         }
 892 }
 893
 894 int transaction_add_job_and_dependencies(
 895                 Transaction *tr,
 896                 JobType type,
 897                 Unit *unit,
 898                 Job *by,
 899                 bool matters,
 900                 bool conflicts,
 901                 bool ignore_requirements,
 902                 bool ignore_order,
 903                 sd_bus_error *e) {
 904
 905         bool is_new;
 906         Unit *dep;
 907         Job *ret;
 908         int r;
 909
 910         assert(tr);
 911         assert(type < _JOB_TYPE_MAX);
 912         assert(type < _JOB_TYPE_MAX_IN_TRANSACTION);
 913         assert(unit);
 914
 915         /* Before adding jobs for this unit, let's ensure that its state has been loaded
 916          * This matters when jobs are spawned as part of coldplugging itself (see e. g. path_coldplug()).
 917          * This way, we "recursively" coldplug units, ensuring that we do not look at state of
 918          * not-yet-coldplugged units. */
 919         if (MANAGER_IS_RELOADING(unit->manager))
 920                 unit_coldplug(unit);
 921
 922         if (by)
 923                 log_trace("Pulling in %s/%s from %s/%s", unit->id, job_type_to_string(type), by->unit->id, job_type_to_string(by->type));
 924
 925         /* Safety check that the unit is a valid state, i.e. not in UNIT_STUB or UNIT_MERGED which should only be set
 926          * temporarily. */
 927         if (!UNIT_IS_LOAD_COMPLETE(unit->load_state))
 928                 return sd_bus_error_setf(e, BUS_ERROR_LOAD_FAILED, "Unit %s is not loaded properly.", unit->id);
 929
 930         if (type != JOB_STOP) {
 931                 r = bus_unit_validate_load_state(unit, e);
 932                 /* The time-based cache allows to start new units without daemon-reload,
 933                  * but if they are already referenced (because of dependencies or ordering)
 934                  * then we have to force a load of the fragment. As an optimization, check
 935                  * first if anything in the usual paths was modified since the last time
 936                  * the cache was loaded. Also check if the last time an attempt to load the
 937                  * unit was made was before the most recent cache refresh, so that we know
 938                  * we need to try again — even if the cache is current, it might have been
 939                  * updated in a different context before we had a chance to retry loading
 940                  * this particular unit.
 941                  *
 942                  * Given building up the transaction is a synchronous operation, attempt
 943                  * to load the unit immediately. */
 944                 if (r < 0 && manager_unit_cache_should_retry_load(unit)) {
 945                         sd_bus_error_free(e);
 946                         unit->load_state = UNIT_STUB;
 947                         r = unit_load(unit);
 948                         if (r < 0 || unit->load_state == UNIT_STUB)
 949                                 unit->load_state = UNIT_NOT_FOUND;
 950                         r = bus_unit_validate_load_state(unit, e);
 951                 }
 952                 if (r < 0)
 953                         return r;
 954         }
 955
 956         if (!unit_job_is_applicable(unit, type))
 957                 return sd_bus_error_setf(e, BUS_ERROR_JOB_TYPE_NOT_APPLICABLE,
 958                                          "Job type %s is not applicable for unit %s.",
 959                                          job_type_to_string(type), unit->id);
 960
 961         /* First add the job. */
 962         ret = transaction_add_one_job(tr, type, unit, &is_new);
 963         if (!ret)
 964                 return -ENOMEM;
 965
 966         ret->ignore_order = ret->ignore_order || ignore_order;
 967
 968         /* Then, add a link to the job. */
 969         if (by) {
 970                 if (!job_dependency_new(by, ret, matters, conflicts))
 971                         return -ENOMEM;
 972         } else {
 973                 /* If the job has no parent job, it is the anchor job. */
 974                 assert(!tr->anchor_job);
 975                 tr->anchor_job = ret;
 976         }
 977
 978         if (is_new && !ignore_requirements && type != JOB_NOP) {
 979                 Set *following;
 980
 981                 /* If we are following some other unit, make sure we
 982                  * add all dependencies of everybody following. */
 983                 if (unit_following_set(ret->unit, &following) > 0) {
 984                         SET_FOREACH(dep, following) {
 985                                 r = transaction_add_job_and_dependencies(tr, type, dep, ret, false, false, false, ignore_order, e);
 986                                 if (r < 0) {
 987                                         log_unit_full_errno(dep, r == -ERFKILL ? LOG_INFO : LOG_WARNING, r,
 988                                                             "Cannot add dependency job, ignoring: %s",
 989                                                             bus_error_message(e, r));
 990                                         sd_bus_error_free(e);
 991                                 }
 992                         }
 993
 994                         set_free(following);
 995                 }
 996
 997                 /* Finally, recursively add in all dependencies. */
 998                 if (IN_SET(type, JOB_START, JOB_RESTART)) {
 999                         UNIT_FOREACH_DEPENDENCY(dep, ret->unit, UNIT_ATOM_PULL_IN_START) {
1000                                 r = transaction_add_job_and_dependencies(tr, JOB_START, dep, ret, true, false, false, ignore_order, e);
1001                                 if (r < 0) {
1002                                         if (r != -EBADR) /* job type not applicable */
1003                                                 return r;
1004
1005                                         sd_bus_error_free(e);
1006                                 }
1007                         }
1008
1009                         UNIT_FOREACH_DEPENDENCY(dep, ret->unit, UNIT_ATOM_PULL_IN_START_IGNORED) {
1010                                 r = transaction_add_job_and_dependencies(tr, JOB_START, dep, ret, false, false, false, ignore_order, e);
1011                                 if (r < 0) {
1012                                         /* unit masked, job type not applicable and unit not found are not considered as errors. */
1013                                         log_unit_full_errno(dep,
1014                                                             IN_SET(r, -ERFKILL, -EBADR, -ENOENT) ? LOG_DEBUG : LOG_WARNING,
1015                                                             r, "Cannot add dependency job, ignoring: %s",
1016                                                             bus_error_message(e, r));
1017                                         sd_bus_error_free(e);
1018                                 }
1019                         }
1020
1021                         UNIT_FOREACH_DEPENDENCY(dep, ret->unit, UNIT_ATOM_PULL_IN_VERIFY) {
1022                                 r = transaction_add_job_and_dependencies(tr, JOB_VERIFY_ACTIVE, dep, ret, true, false, false, ignore_order, e);
1023                                 if (r < 0) {
1024                                         if (r != -EBADR) /* job type not applicable */
1025                                                 return r;
1026
1027                                         sd_bus_error_free(e);
1028                                 }
1029                         }
1030
1031                         UNIT_FOREACH_DEPENDENCY(dep, ret->unit, UNIT_ATOM_PULL_IN_STOP) {
1032                                 r = transaction_add_job_and_dependencies(tr, JOB_STOP, dep, ret, true, true, false, ignore_order, e);
1033                                 if (r < 0) {
1034                                         if (r != -EBADR) /* job type not applicable */
1035                                                 return r;
1036
1037                                         sd_bus_error_free(e);
1038                                 }
1039                         }
1040
1041                         UNIT_FOREACH_DEPENDENCY(dep, ret->unit, UNIT_ATOM_PULL_IN_STOP_IGNORED) {
1042                                 r = transaction_add_job_and_dependencies(tr, JOB_STOP, dep, ret, false, false, false, ignore_order, e);
1043                                 if (r < 0) {
1044                                         log_unit_warning(dep,
1045                                                          "Cannot add dependency job, ignoring: %s",
1046                                                          bus_error_message(e, r));
1047                                         sd_bus_error_free(e);
1048                                 }
1049                         }
1050                 }
1051
1052                 if (IN_SET(type, JOB_STOP, JOB_RESTART)) {
1053                         UnitDependencyAtom atom;
1054                         JobType ptype;
1055
1056                         /* We propagate STOP as STOP, but RESTART only as TRY_RESTART, in order not to start
1057                          * dependencies that are not around. */
1058                         if (type == JOB_RESTART) {
1059                                 atom = UNIT_ATOM_PROPAGATE_RESTART;
1060                                 ptype = JOB_TRY_RESTART;
1061                         } else {
1062                                 ptype = JOB_STOP;
1063                                 atom = UNIT_ATOM_PROPAGATE_STOP;
1064                         }
1065
1066                         UNIT_FOREACH_DEPENDENCY(dep, ret->unit, atom) {
1067                                 JobType nt;
1068
1069                                 nt = job_type_collapse(ptype, dep);
1070                                 if (nt == JOB_NOP)
1071                                         continue;
1072
1073                                 r = transaction_add_job_and_dependencies(tr, nt, dep, ret, true, false, false, ignore_order, e);
1074                                 if (r < 0) {
1075                                         if (r != -EBADR) /* job type not applicable */
1076                                                 return r;
1077
1078                                         sd_bus_error_free(e);
1079                                 }
1080                         }
1081                 }
1082
1083                 if (type == JOB_RELOAD)
1084                         transaction_add_propagate_reload_jobs(tr, ret->unit, ret, ignore_order, e);
1085
1086                 /* JOB_VERIFY_ACTIVE requires no dependency handling */
1087         }
1088
1089         return 0;
1090 }
1091
1092 int transaction_add_isolate_jobs(Transaction *tr, Manager *m) {
1093         Unit *u;
1094         char *k;
1095         int r;
1096
1097         assert(tr);
1098         assert(m);
1099
1100         HASHMAP_FOREACH_KEY(u, k, m->units) {
1101
1102                 /* ignore aliases */
1103                 if (u->id != k)
1104                         continue;
1105
1106                 if (u->ignore_on_isolate)
1107                         continue;
1108
1109                 /* No need to stop inactive jobs */
1110                 if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(u)) && !u->job)
1111                         continue;
1112
1113                 /* Is there already something listed for this? */
1114                 if (hashmap_get(tr->jobs, u))
1115                         continue;
1116
1117                 r = transaction_add_job_and_dependencies(tr, JOB_STOP, u, tr->anchor_job, true, false, false, false, NULL);
1118                 if (r < 0)
1119                         log_unit_warning_errno(u, r, "Cannot add isolate job, ignoring: %m");
1120         }
1121
1122         return 0;
1123 }
1124
1125 int transaction_add_triggering_jobs(Transaction *tr, Unit *u) {
1126         Unit *trigger;
1127         int r;
1128
1129         assert(tr);
1130         assert(u);
1131
1132         UNIT_FOREACH_DEPENDENCY(trigger, u, UNIT_ATOM_TRIGGERED_BY) {
1133
1134                 /* No need to stop inactive jobs */
1135                 if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(trigger)) && !trigger->job)
1136                         continue;
1137
1138                 /* Is there already something listed for this? */
1139                 if (hashmap_get(tr->jobs, trigger))
1140                         continue;
1141
1142                 r = transaction_add_job_and_dependencies(tr, JOB_STOP, trigger, tr->anchor_job, true, false, false, false, NULL);
1143                 if (r < 0)
1144                         log_unit_warning_errno(u, r, "Cannot add triggered by job, ignoring: %m");
1145         }
1146
1147         return 0;
1148 }
1149
1150 Transaction *transaction_new(bool irreversible) {
1151         Transaction *tr;
1152
1153         tr = new0(Transaction, 1);
1154         if (!tr)
1155                 return NULL;
1156
1157         tr->jobs = hashmap_new(NULL);
1158         if (!tr->jobs)
1159                 return mfree(tr);
1160
1161         tr->irreversible = irreversible;
1162
1163         return tr;
1164 }
1165
1166 void transaction_free(Transaction *tr) {
1167         assert(hashmap_isempty(tr->jobs));
1168         hashmap_free(tr->jobs);
1169         free(tr);
1170 }