include/qemu/job.h

   1 /*
   2  * Declarations for background jobs
   3  *
   4  * Copyright (c) 2011 IBM Corp.
   5  * Copyright (c) 2012, 2018 Red Hat, Inc.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #ifndef JOB_H
  27 #define JOB_H
  28
  29 #include "qapi/qapi-types-job.h"
  30 #include "qemu/queue.h"
  31 #include "qemu/progress_meter.h"
  32 #include "qemu/coroutine.h"
  33 #include "block/aio.h"
  34
  35 typedef struct JobDriver JobDriver;
  36 typedef struct JobTxn JobTxn;
  37
  38
  39 /**
  40  * Long-running operation.
  41  */
  42 typedef struct Job {
  43
  44     /* Fields set at initialization (job_create), and never modified */
  45
  46     /** The ID of the job. May be NULL for internal jobs. */
  47     char *id;
  48
  49     /**
  50      * The type of this job.
  51      * All callbacks are called with job_mutex *not* held.
  52      */
  53     const JobDriver *driver;
  54
  55     /**
  56      * The coroutine that executes the job.  If not NULL, it is reentered when
  57      * busy is false and the job is cancelled.
  58      * Initialized in job_start()
  59      */
  60     Coroutine *co;
  61
  62     /** True if this job should automatically finalize itself */
  63     bool auto_finalize;
  64
  65     /** True if this job should automatically dismiss itself */
  66     bool auto_dismiss;
  67
  68     /**
  69      * The completion function that will be called when the job completes.
  70      */
  71     BlockCompletionFunc *cb;
  72
  73     /** The opaque value that is passed to the completion function.  */
  74     void *opaque;
  75
  76     /* ProgressMeter API is thread-safe */
  77     ProgressMeter progress;
  78
  79     /**
  80      * AioContext to run the job coroutine in.
  81      * The job Aiocontext can be read when holding *either*
  82      * the BQL (so we are in the main loop) or the job_mutex.
  83      * It can only be written when we hold *both* BQL
  84      * and the job_mutex.
  85      */
  86     AioContext *aio_context;
  87
  88
  89     /** Protected by job_mutex */
  90
  91     /** Reference count of the block job */
  92     int refcnt;
  93
  94     /** Current state; See @JobStatus for details. */
  95     JobStatus status;
  96
  97     /**
  98      * Timer that is used by @job_sleep_ns. Accessed under job_mutex (in
  99      * job.c).
 100      */
 101     QEMUTimer sleep_timer;
 102
 103     /**
 104      * Counter for pause request. If non-zero, the block job is either paused,
 105      * or if busy == true will pause itself as soon as possible.
 106      */
 107     int pause_count;
 108
 109     /**
 110      * Set to false by the job while the coroutine has yielded and may be
 111      * re-entered by job_enter(). There may still be I/O or event loop activity
 112      * pending. Accessed under job_mutex.
 113      *
 114      * When the job is deferred to the main loop, busy is true as long as the
 115      * bottom half is still pending.
 116      */
 117     bool busy;
 118
 119     /**
 120      * Set to true by the job while it is in a quiescent state, where
 121      * no I/O or event loop activity is pending.
 122      */
 123     bool paused;
 124
 125     /**
 126      * Set to true if the job is paused by user.  Can be unpaused with the
 127      * block-job-resume QMP command.
 128      */
 129     bool user_paused;
 130
 131     /**
 132      * Set to true if the job should cancel itself.  The flag must
 133      * always be tested just before toggling the busy flag from false
 134      * to true.  After a job has been cancelled, it should only yield
 135      * if #aio_poll will ("sooner or later") reenter the coroutine.
 136      */
 137     bool cancelled;
 138
 139     /**
 140      * Set to true if the job should abort immediately without waiting
 141      * for data to be in sync.
 142      */
 143     bool force_cancel;
 144
 145     /** Set to true when the job has deferred work to the main loop. */
 146     bool deferred_to_main_loop;
 147
 148     /**
 149      * Return code from @run and/or @prepare callback(s).
 150      * Not final until the job has reached the CONCLUDED status.
 151      * 0 on success, -errno on failure.
 152      */
 153     int ret;
 154
 155     /**
 156      * Error object for a failed job.
 157      * If job->ret is nonzero and an error object was not set, it will be set
 158      * to strerror(-job->ret) during job_completed.
 159      */
 160     Error *err;
 161
 162     /** Notifiers called when a cancelled job is finalised */
 163     NotifierList on_finalize_cancelled;
 164
 165     /** Notifiers called when a successfully completed job is finalised */
 166     NotifierList on_finalize_completed;
 167
 168     /** Notifiers called when the job transitions to PENDING */
 169     NotifierList on_pending;
 170
 171     /** Notifiers called when the job transitions to READY */
 172     NotifierList on_ready;
 173
 174     /** Notifiers called when the job coroutine yields or terminates */
 175     NotifierList on_idle;
 176
 177     /** Element of the list of jobs */
 178     QLIST_ENTRY(Job) job_list;
 179
 180     /** Transaction this job is part of */
 181     JobTxn *txn;
 182
 183     /** Element of the list of jobs in a job transaction */
 184     QLIST_ENTRY(Job) txn_list;
 185 } Job;
 186
 187 /**
 188  * Callbacks and other information about a Job driver.
 189  * All callbacks are invoked with job_mutex *not* held.
 190  */
 191 struct JobDriver {
 192
 193     /*
 194      * These fields are initialized when this object is created,
 195      * and are never changed afterwards
 196      */
 197
 198     /** Derived Job struct size */
 199     size_t instance_size;
 200
 201     /** Enum describing the operation */
 202     JobType job_type;
 203
 204     /**
 205      * Mandatory: Entrypoint for the Coroutine.
 206      *
 207      * This callback will be invoked when moving from CREATED to RUNNING.
 208      *
 209      * If this callback returns nonzero, the job transaction it is part of is
 210      * aborted. If it returns zero, the job moves into the WAITING state. If it
 211      * is the last job to complete in its transaction, all jobs in the
 212      * transaction move from WAITING to PENDING.
 213      *
 214      * This callback must be run in the job's context.
 215      */
 216     int coroutine_fn (*run)(Job *job, Error **errp);
 217
 218     /*
 219      * Functions run without regard to the BQL that may run in any
 220      * arbitrary thread. These functions do not need to be thread-safe
 221      * because the caller ensures that they are invoked from one
 222      * thread at time.
 223      */
 224
 225     /**
 226      * If the callback is not NULL, it will be invoked when the job transitions
 227      * into the paused state.  Paused jobs must not perform any asynchronous
 228      * I/O or event loop activity.  This callback is used to quiesce jobs.
 229      */
 230     void coroutine_fn (*pause)(Job *job);
 231
 232     /**
 233      * If the callback is not NULL, it will be invoked when the job transitions
 234      * out of the paused state.  Any asynchronous I/O or event loop activity
 235      * should be restarted from this callback.
 236      */
 237     void coroutine_fn (*resume)(Job *job);
 238
 239     /*
 240      * Global state (GS) API. These functions run under the BQL.
 241      *
 242      * See include/block/block-global-state.h for more information about
 243      * the GS API.
 244      */
 245
 246     /**
 247      * Called when the job is resumed by the user (i.e. user_paused becomes
 248      * false). .user_resume is called before .resume.
 249      */
 250     void (*user_resume)(Job *job);
 251
 252     /**
 253      * Optional callback for job types whose completion must be triggered
 254      * manually.
 255      */
 256     void (*complete)(Job *job, Error **errp);
 257
 258     /**
 259      * If the callback is not NULL, prepare will be invoked when all the jobs
 260      * belonging to the same transaction complete; or upon this job's completion
 261      * if it is not in a transaction.
 262      *
 263      * This callback will not be invoked if the job has already failed.
 264      * If it fails, abort and then clean will be called.
 265      */
 266     int (*prepare)(Job *job);
 267
 268     /**
 269      * If the callback is not NULL, it will be invoked when all the jobs
 270      * belonging to the same transaction complete; or upon this job's
 271      * completion if it is not in a transaction. Skipped if NULL.
 272      *
 273      * All jobs will complete with a call to either .commit() or .abort() but
 274      * never both.
 275      */
 276     void (*commit)(Job *job);
 277
 278     /**
 279      * If the callback is not NULL, it will be invoked when any job in the
 280      * same transaction fails; or upon this job's failure (due to error or
 281      * cancellation) if it is not in a transaction. Skipped if NULL.
 282      *
 283      * All jobs will complete with a call to either .commit() or .abort() but
 284      * never both.
 285      */
 286     void (*abort)(Job *job);
 287
 288     /**
 289      * If the callback is not NULL, it will be invoked after a call to either
 290      * .commit() or .abort(). Regardless of which callback is invoked after
 291      * completion, .clean() will always be called, even if the job does not
 292      * belong to a transaction group.
 293      */
 294     void (*clean)(Job *job);
 295
 296     /**
 297      * If the callback is not NULL, it will be invoked in job_cancel_async
 298      *
 299      * This function must return true if the job will be cancelled
 300      * immediately without any further I/O (mandatory if @force is
 301      * true), and false otherwise.  This lets the generic job layer
 302      * know whether a job has been truly (force-)cancelled, or whether
 303      * it is just in a special completion mode (like mirror after
 304      * READY).
 305      * (If the callback is NULL, the job is assumed to terminate
 306      * without I/O.)
 307      */
 308     bool (*cancel)(Job *job, bool force);
 309
 310
 311     /**
 312      * Called when the job is freed.
 313      */
 314     void (*free)(Job *job);
 315 };
 316
 317 typedef enum JobCreateFlags {
 318     /* Default behavior */
 319     JOB_DEFAULT = 0x00,
 320     /* Job is not QMP-created and should not send QMP events */
 321     JOB_INTERNAL = 0x01,
 322     /* Job requires manual finalize step */
 323     JOB_MANUAL_FINALIZE = 0x02,
 324     /* Job requires manual dismiss step */
 325     JOB_MANUAL_DISMISS = 0x04,
 326 } JobCreateFlags;
 327
 328 extern QemuMutex job_mutex;
 329
 330 #define JOB_LOCK_GUARD() QEMU_LOCK_GUARD(&job_mutex)
 331
 332 #define WITH_JOB_LOCK_GUARD() WITH_QEMU_LOCK_GUARD(&job_mutex)
 333
 334 /**
 335  * job_lock:
 336  *
 337  * Take the mutex protecting the list of jobs and their status.
 338  * Most functions called by the monitor need to call job_lock
 339  * and job_unlock manually.  On the other hand, function called
 340  * by the block jobs themselves and by the block layer will take the
 341  * lock for you.
 342  */
 343 void job_lock(void);
 344
 345 /**
 346  * job_unlock:
 347  *
 348  * Release the mutex protecting the list of jobs and their status.
 349  */
 350 void job_unlock(void);
 351
 352 /**
 353  * Allocate and return a new job transaction. Jobs can be added to the
 354  * transaction using job_txn_add_job().
 355  *
 356  * The transaction is automatically freed when the last job completes or is
 357  * cancelled.
 358  *
 359  * All jobs in the transaction either complete successfully or fail/cancel as a
 360  * group.  Jobs wait for each other before completing.  Cancelling one job
 361  * cancels all jobs in the transaction.
 362  */
 363 JobTxn *job_txn_new(void);
 364
 365 /**
 366  * Release a reference that was previously acquired with job_txn_add_job or
 367  * job_txn_new. If it's the last reference to the object, it will be freed.
 368  *
 369  * Called with job lock *not* held.
 370  */
 371 void job_txn_unref(JobTxn *txn);
 372
 373 /*
 374  * Same as job_txn_unref(), but called with job lock held.
 375  * Might release the lock temporarily.
 376  */
 377 void job_txn_unref_locked(JobTxn *txn);
 378
 379 /**
 380  * Create a new long-running job and return it.
 381  * Called with job_mutex *not* held.
 382  *
 383  * @job_id: The id of the newly-created job, or %NULL for internal jobs
 384  * @driver: The class object for the newly-created job.
 385  * @txn: The transaction this job belongs to, if any. %NULL otherwise.
 386  * @ctx: The AioContext to run the job coroutine in.
 387  * @flags: Creation flags for the job. See @JobCreateFlags.
 388  * @cb: Completion function for the job.
 389  * @opaque: Opaque pointer value passed to @cb.
 390  * @errp: Error object.
 391  */
 392 void *job_create(const char *job_id, const JobDriver *driver, JobTxn *txn,
 393                  AioContext *ctx, int flags, BlockCompletionFunc *cb,
 394                  void *opaque, Error **errp);
 395
 396 /**
 397  * Add a reference to Job refcnt, it will be decreased with job_unref, and then
 398  * be freed if it comes to be the last reference.
 399  *
 400  * Called with job lock held.
 401  */
 402 void job_ref_locked(Job *job);
 403
 404 /**
 405  * Release a reference that was previously acquired with job_ref_locked() or
 406  * job_create(). If it's the last reference to the object, it will be freed.
 407  *
 408  * Called with job lock held.
 409  */
 410 void job_unref_locked(Job *job);
 411
 412 /**
 413  * @job: The job that has made progress
 414  * @done: How much progress the job made since the last call
 415  *
 416  * Updates the progress counter of the job.
 417  *
 418  * May be called with mutex held or not held.
 419  */
 420 void job_progress_update(Job *job, uint64_t done);
 421
 422 /**
 423  * @job: The job whose expected progress end value is set
 424  * @remaining: Missing progress (on top of the current progress counter value)
 425  *             until the new expected end value is reached
 426  *
 427  * Sets the expected end value of the progress counter of a job so that a
 428  * completion percentage can be calculated when the progress is updated.
 429  *
 430  * May be called with mutex held or not held.
 431  */
 432 void job_progress_set_remaining(Job *job, uint64_t remaining);
 433
 434 /**
 435  * @job: The job whose expected progress end value is updated
 436  * @delta: Value which is to be added to the current expected end
 437  *         value
 438  *
 439  * Increases the expected end value of the progress counter of a job.
 440  * This is useful for parenthesis operations: If a job has to
 441  * conditionally perform a high-priority operation as part of its
 442  * progress, it calls this function with the expected operation's
 443  * length before, and job_progress_update() afterwards.
 444  * (So the operation acts as a parenthesis in regards to the main job
 445  * operation running in background.)
 446  *
 447  * May be called with mutex held or not held.
 448  */
 449 void job_progress_increase_remaining(Job *job, uint64_t delta);
 450
 451 /**
 452  * Conditionally enter the job coroutine if the job is ready to run, not
 453  * already busy and fn() returns true. fn() is called while under the job_lock
 454  * critical section.
 455  *
 456  * Called with job lock held, but might release it temporarily.
 457  */
 458 void job_enter_cond_locked(Job *job, bool(*fn)(Job *job));
 459
 460 /**
 461  * @job: A job that has not yet been started.
 462  *
 463  * Begins execution of a job.
 464  * Takes ownership of one reference to the job object.
 465  *
 466  * Called with job_mutex *not* held.
 467  */
 468 void job_start(Job *job);
 469
 470 /**
 471  * @job: The job to enter.
 472  *
 473  * Continue the specified job by entering the coroutine.
 474  * Called with job_mutex *not* held.
 475  */
 476 void job_enter(Job *job);
 477
 478 /**
 479  * @job: The job that is ready to pause.
 480  *
 481  * Pause now if job_pause() has been called. Jobs that perform lots of I/O
 482  * must call this between requests so that the job can be paused.
 483  *
 484  * Called with job_mutex *not* held.
 485  */
 486 void coroutine_fn job_pause_point(Job *job);
 487
 488 /**
 489  * @job: The job that calls the function.
 490  *
 491  * Yield the job coroutine.
 492  * Called with job_mutex *not* held.
 493  */
 494 void coroutine_fn job_yield(Job *job);
 495
 496 /**
 497  * @job: The job that calls the function.
 498  * @ns: How many nanoseconds to stop for.
 499  *
 500  * Put the job to sleep (assuming that it wasn't canceled) for @ns
 501  * %QEMU_CLOCK_REALTIME nanoseconds.  Canceling the job will immediately
 502  * interrupt the wait.
 503  *
 504  * Called with job_mutex *not* held.
 505  */
 506 void coroutine_fn job_sleep_ns(Job *job, int64_t ns);
 507
 508 /** Returns the JobType of a given Job. */
 509 JobType job_type(const Job *job);
 510
 511 /** Returns the enum string for the JobType of a given Job. */
 512 const char *job_type_str(const Job *job);
 513
 514 /** Returns true if the job should not be visible to the management layer. */
 515 bool job_is_internal(Job *job);
 516
 517 /**
 518  * Returns whether the job is being cancelled.
 519  * Called with job_mutex *not* held.
 520  */
 521 bool job_is_cancelled(Job *job);
 522
 523 /* Same as job_is_cancelled(), but called with job lock held. */
 524 bool job_is_cancelled_locked(Job *job);
 525
 526 /**
 527  * Returns whether the job is scheduled for cancellation (at an
 528  * indefinite point).
 529  * Called with job_mutex *not* held.
 530  */
 531 bool job_cancel_requested(Job *job);
 532
 533 /**
 534  * Returns whether the job is in a completed state.
 535  * Called with job lock held.
 536  */
 537 bool job_is_completed_locked(Job *job);
 538
 539 /**
 540  * Returns whether the job is ready to be completed.
 541  * Called with job_mutex *not* held.
 542  */
 543 bool job_is_ready(Job *job);
 544
 545 /* Same as job_is_ready(), but called with job lock held. */
 546 bool job_is_ready_locked(Job *job);
 547
 548 /**
 549  * Request @job to pause at the next pause point. Must be paired with
 550  * job_resume(). If the job is supposed to be resumed by user action, call
 551  * job_user_pause_locked() instead.
 552  *
 553  * Called with job lock *not* held.
 554  */
 555 void job_pause(Job *job);
 556
 557 /* Same as job_pause(), but called with job lock held. */
 558 void job_pause_locked(Job *job);
 559
 560 /** Resumes a @job paused with job_pause. Called with job lock *not* held. */
 561 void job_resume(Job *job);
 562
 563 /*
 564  * Same as job_resume(), but called with job lock held.
 565  * Might release the lock temporarily.
 566  */
 567 void job_resume_locked(Job *job);
 568
 569 /**
 570  * Asynchronously pause the specified @job.
 571  * Do not allow a resume until a matching call to job_user_resume.
 572  * Called with job lock held.
 573  */
 574 void job_user_pause_locked(Job *job, Error **errp);
 575
 576 /**
 577  * Returns true if the job is user-paused.
 578  * Called with job lock held.
 579  */
 580 bool job_user_paused_locked(Job *job);
 581
 582 /**
 583  * Resume the specified @job.
 584  * Must be paired with a preceding job_user_pause_locked.
 585  * Called with job lock held, but might release it temporarily.
 586  */
 587 void job_user_resume_locked(Job *job, Error **errp);
 588
 589 /**
 590  * Get the next element from the list of block jobs after @job, or the
 591  * first one if @job is %NULL.
 592  *
 593  * Returns the requested job, or %NULL if there are no more jobs left.
 594  * Called with job lock *not* held.
 595  */
 596 Job *job_next(Job *job);
 597
 598 /* Same as job_next(), but called with job lock held. */
 599 Job *job_next_locked(Job *job);
 600
 601 /**
 602  * Get the job identified by @id (which must not be %NULL).
 603  *
 604  * Returns the requested job, or %NULL if it doesn't exist.
 605  * Called with job lock held.
 606  */
 607 Job *job_get_locked(const char *id);
 608
 609 /**
 610  * Check whether the verb @verb can be applied to @job in its current state.
 611  * Returns 0 if the verb can be applied; otherwise errp is set and -EPERM
 612  * returned.
 613  *
 614  * Called with job lock held.
 615  */
 616 int job_apply_verb_locked(Job *job, JobVerb verb, Error **errp);
 617
 618 /**
 619  * The @job could not be started, free it.
 620  * Called with job_mutex *not* held.
 621  */
 622 void job_early_fail(Job *job);
 623
 624 /**
 625  * Moves the @job from RUNNING to READY.
 626  * Called with job_mutex *not* held.
 627  */
 628 void job_transition_to_ready(Job *job);
 629
 630 /**
 631  * Asynchronously complete the specified @job.
 632  * Called with job lock held, but might release it temporarily.
 633  */
 634 void job_complete_locked(Job *job, Error **errp);
 635
 636 /**
 637  * Asynchronously cancel the specified @job. If @force is true, the job should
 638  * be cancelled immediately without waiting for a consistent state.
 639  * Called with job lock held.
 640  */
 641 void job_cancel_locked(Job *job, bool force);
 642
 643 /**
 644  * Cancels the specified job like job_cancel_locked(), but may refuse
 645  * to do so if the operation isn't meaningful in the current state of the job.
 646  * Called with job lock held.
 647  */
 648 void job_user_cancel_locked(Job *job, bool force, Error **errp);
 649
 650 /**
 651  * Synchronously cancel the @job.  The completion callback is called
 652  * before the function returns.  If @force is false, the job may
 653  * actually complete instead of canceling itself; the circumstances
 654  * under which this happens depend on the kind of job that is active.
 655  *
 656  * Returns the return value from the job if the job actually completed
 657  * during the call, or -ECANCELED if it was canceled.
 658  *
 659  * Called with job_lock *not* held.
 660  */
 661 int job_cancel_sync(Job *job, bool force);
 662
 663 /* Same as job_cancel_sync, but called with job lock held. */
 664 int job_cancel_sync_locked(Job *job, bool force);
 665
 666 /**
 667  * Synchronously force-cancels all jobs using job_cancel_sync_locked().
 668  *
 669  * Called with job_lock *not* held.
 670  */
 671 void job_cancel_sync_all(void);
 672
 673 /**
 674  * @job: The job to be completed.
 675  * @errp: Error object which may be set by job_complete_locked(); this is not
 676  *        necessarily set on every error, the job return value has to be
 677  *        checked as well.
 678  *
 679  * Synchronously complete the job.  The completion callback is called before the
 680  * function returns, unless it is NULL (which is permissible when using this
 681  * function).
 682  *
 683  * Returns the return value from the job.
 684  * Called with job_lock held.
 685  */
 686 int job_complete_sync_locked(Job *job, Error **errp);
 687
 688 /**
 689  * For a @job that has finished its work and is pending awaiting explicit
 690  * acknowledgement to commit its work, this will commit that work.
 691  *
 692  * FIXME: Make the below statement universally true:
 693  * For jobs that support the manual workflow mode, all graph changes that occur
 694  * as a result will occur after this command and before a successful reply.
 695  *
 696  * Called with job lock held.
 697  */
 698 void job_finalize_locked(Job *job, Error **errp);
 699
 700 /**
 701  * Remove the concluded @job from the query list and resets the passed pointer
 702  * to %NULL. Returns an error if the job is not actually concluded.
 703  *
 704  * Called with job lock held.
 705  */
 706 void job_dismiss_locked(Job **job, Error **errp);
 707
 708 /**
 709  * Synchronously finishes the given @job. If @finish is given, it is called to
 710  * trigger completion or cancellation of the job.
 711  *
 712  * Returns 0 if the job is successfully completed, -ECANCELED if the job was
 713  * cancelled before completing, and -errno in other error cases.
 714  *
 715  * Called with job_lock held, but might release it temporarily.
 716  */
 717 int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error **errp),
 718                            Error **errp);
 719
 720 /**
 721  * Sets the @job->aio_context.
 722  * Called with job_mutex *not* held.
 723  *
 724  * This function must run in the main thread to protect against
 725  * concurrent read in job_finish_sync_locked(), takes the job_mutex
 726  * lock to protect against the read in job_do_yield_locked(), and must
 727  * be called when the job is quiescent.
 728  */
 729 void job_set_aio_context(Job *job, AioContext *ctx);
 730
 731 #endif