Boot Linux faster!

Check our new training course

Boot Linux faster!

Check our new training course
and Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
/*
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file
 *
 * Second generation work queue implementation
 */

#include <kernel.h>
#include <kernel_structs.h>
#include <wait_q.h>
#include <spinlock.h>
#include <errno.h>
#include <ksched.h>
#include <sys/printk.h>

static inline void flag_clear(uint32_t *flagp,
			      uint32_t bit)
{
	*flagp &= ~BIT(bit);
}

static inline void flag_set(uint32_t *flagp,
			    uint32_t bit)
{
	*flagp |= BIT(bit);
}

static inline bool flag_test(const uint32_t *flagp,
			     uint32_t bit)
{
	return (*flagp & BIT(bit)) != 0U;
}

static inline bool flag_test_and_clear(uint32_t *flagp,
				       int bit)
{
	bool ret = flag_test(flagp, bit);

	flag_clear(flagp, bit);

	return ret;
}

static inline void flags_set(uint32_t *flagp,
			     uint32_t flags)
{
	*flagp = flags;
}

static inline uint32_t flags_get(const uint32_t *flagp)
{
	return *flagp;
}

/* Lock to protect the internal state of all work items, work queues,
 * and pending_cancels.
 */
static struct k_spinlock lock;

/* Invoked by work thread */
static void handle_flush(struct k_work *work)
{
	struct z_work_flusher *flusher
		= CONTAINER_OF(work, struct z_work_flusher, work);

	k_sem_give(&flusher->sem);
}

static inline void init_flusher(struct z_work_flusher *flusher)
{
	k_sem_init(&flusher->sem, 0, 1);
	k_work_init(&flusher->work, handle_flush);
}

/* List of pending cancellations. */
static sys_slist_t pending_cancels;

/* Initialize a canceler record and add it to the list of pending
 * cancels.
 *
 * Invoked with work lock held.
 *
 * @param canceler the structure used to notify a waiting process.
 * @param work the work structure that is to be canceled
 */
static inline void init_work_cancel(struct z_work_canceller *canceler,
				    struct k_work *work)
{
	k_sem_init(&canceler->sem, 0, 1);
	canceler->work = work;
	sys_slist_append(&pending_cancels, &canceler->node);
}

/* Complete cancellation of a work item and unlock held lock.
 *
 * Invoked with work lock held.
 *
 * Invoked from a work queue thread.
 *
 * Reschedules.
 *
 * @param work the work structre that has completed cancellation
 */
static void finalize_cancel_locked(struct k_work *work)
{
	struct z_work_canceller *wc, *tmp;
	sys_snode_t *prev = NULL;

	/* Clear this first, so released high-priority threads don't
	 * see it when doing things.
	 */
	flag_clear(&work->flags, K_WORK_CANCELING_BIT);

	/* Search for and remove the matching container, and release
	 * what's waiting for the completion.  The same work item can
	 * appear multiple times in the list if multiple threads
	 * attempt to cancel it.
	 */
	SYS_SLIST_FOR_EACH_CONTAINER_SAFE(&pending_cancels, wc, tmp, node) {
		if (wc->work == work) {
			sys_slist_remove(&pending_cancels, prev, &wc->node);
			k_sem_give(&wc->sem);
		} else {
			prev = &wc->node;
		}
	}
}

void k_work_init(struct k_work *work,
		  k_work_handler_t handler)
{
	__ASSERT_NO_MSG(work != NULL);
	__ASSERT_NO_MSG(handler != NULL);

	*work = (struct k_work)Z_WORK_INITIALIZER(handler);

	SYS_PORT_TRACING_OBJ_INIT(k_work, work);
}

static inline int work_busy_get_locked(const struct k_work *work)
{
	return flags_get(&work->flags) & K_WORK_MASK;
}

int k_work_busy_get(const struct k_work *work)
{
	k_spinlock_key_t key = k_spin_lock(&lock);
	int ret = work_busy_get_locked(work);

	k_spin_unlock(&lock, key);

	return ret;
}

/* Add a flusher work item to the queue.
 *
 * Invoked with work lock held.
 *
 * Caller must notify queue of pending work.
 *
 * @param queue queue on which a work item may appear.
 * @param work the work item that is either queued or running on @p
 * queue
 * @param flusher an uninitialized/unused flusher object
 */
static void queue_flusher_locked(struct k_work_q *queue,
				 struct k_work *work,
				 struct z_work_flusher *flusher)
{
	bool in_list = false;
	struct k_work *wn;

	/* Determine whether the work item is still queued. */
	SYS_SLIST_FOR_EACH_CONTAINER(&queue->pending, wn, node) {
		if (wn == work) {
			in_list = true;
			break;
		}
	}

	init_flusher(flusher);
	if (in_list) {
		sys_slist_insert(&queue->pending, &work->node,
				 &flusher->work.node);
	} else {
		sys_slist_prepend(&queue->pending, &flusher->work.node);
	}
}

/* Try to remove a work item from the given queue.
 *
 * Invoked with work lock held.
 *
 * @param queue the queue from which the work should be removed
 * @param work work that may be on the queue
 */
static inline void queue_remove_locked(struct k_work_q *queue,
				       struct k_work *work)
{
	if (flag_test_and_clear(&work->flags, K_WORK_QUEUED_BIT)) {
		(void)sys_slist_find_and_remove(&queue->pending, &work->node);
	}
}

/* Potentially notify a queue that it needs to look for pending work.
 *
 * This may make the work queue thread ready, but as the lock is held it
 * will not be a reschedule point.  Callers should yield after the lock is
 * released where appropriate (generally if this returns true).
 *
 * @param queue to be notified.  If this is null no notification is required.
 *
 * @return true if and only if the queue was notified and woken, i.e. a
 * reschedule is pending.
 */
static inline bool notify_queue_locked(struct k_work_q *queue)
{
	bool rv = false;

	if (queue != NULL) {
		rv = z_sched_wake(&queue->notifyq, 0, NULL);
	}

	return rv;
}

/* Submit an work item to a queue if queue state allows new work.
 *
 * Submission is rejected if no queue is provided, or if the queue is
 * draining and the work isn't being submitted from the queue's
 * thread (chained submission).
 *
 * Invoked with work lock held.
 * Conditionally notifies queue.
 *
 * @param queue the queue to which work should be submitted.  This may
 * be null, in which case the submission will fail.
 *
 * @param work to be submitted
 *
 * @retval 1 if successfully queued
 * @retval -EINVAL if no queue is provided
 * @retval -ENODEV if the queue is not started
 * @retval -EBUSY if the submission was rejected (draining, plugged)
 */
static inline int queue_submit_locked(struct k_work_q *queue,
				      struct k_work *work)
{
	if (queue == NULL) {
		return -EINVAL;
	}

	int ret = -EBUSY;
	bool chained = (_current == &queue->thread) && !k_is_in_isr();
	bool draining = flag_test(&queue->flags, K_WORK_QUEUE_DRAIN_BIT);
	bool plugged = flag_test(&queue->flags, K_WORK_QUEUE_PLUGGED_BIT);

	/* Test for acceptability, in priority order:
	 *
	 * * -ENODEV if the queue isn't running.
	 * * -EBUSY if draining and not chained
	 * * -EBUSY if plugged and not draining
	 * * otherwise OK
	 */
	if (!flag_test(&queue->flags, K_WORK_QUEUE_STARTED_BIT)) {
		ret = -ENODEV;
	} else if (draining && !chained) {
		ret = -EBUSY;
	} else if (plugged && !draining) {
		ret = -EBUSY;
	} else {
		sys_slist_append(&queue->pending, &work->node);
		ret = 1;
		(void)notify_queue_locked(queue);
	}

	return ret;
}

/* Attempt to submit work to a queue.
 *
 * The submission can fail if:
 * * the work is cancelling,
 * * no candidate queue can be identified;
 * * the candidate queue rejects the submission.
 *
 * Invoked with work lock held.
 * Conditionally notifies queue.
 *
 * @param work the work structure to be submitted

 * @param queuep pointer to a queue reference.  On input this should
 * dereference to the proposed queue (which may be null); after completion it
 * will be null if the work was not submitted or if submitted will reference
 * the queue it was submitted to.  That may or may not be the queue provided
 * on input.
 *
 * @retval 0 if work was already submitted to a queue
 * @retval 1 if work was not submitted and has been queued to @p queue
 * @retval 2 if work was running and has been queued to the queue that was
 * running it
 * @retval -EBUSY if canceling or submission was rejected by queue
 * @retval -EINVAL if no queue is provided
 * @retval -ENODEV if the queue is not started
 */
static int submit_to_queue_locked(struct k_work *work,
				  struct k_work_q **queuep)
{
	int ret = 0;

	if (flag_test(&work->flags, K_WORK_CANCELING_BIT)) {
		/* Disallowed */
		ret = -EBUSY;
	} else if (!flag_test(&work->flags, K_WORK_QUEUED_BIT)) {
		/* Not currently queued */
		ret = 1;

		/* If no queue specified resubmit to last queue.
		 */
		if (*queuep == NULL) {
			*queuep = work->queue;
		}

		/* If the work is currently running we have to use the
		 * queue it's running on to prevent handler
		 * re-entrancy.
		 */
		if (flag_test(&work->flags, K_WORK_RUNNING_BIT)) {
			__ASSERT_NO_MSG(work->queue != NULL);
			*queuep = work->queue;
			ret = 2;
		}

		int rc = queue_submit_locked(*queuep, work);

		if (rc < 0) {
			ret = rc;
		} else {
			flag_set(&work->flags, K_WORK_QUEUED_BIT);
			work->queue = *queuep;
		}
	} else {
		/* Already queued, do nothing. */
	}

	if (ret <= 0) {
		*queuep = NULL;
	}

	return ret;
}

int k_work_submit_to_queue(struct k_work_q *queue,
			    struct k_work *work)
{
	__ASSERT_NO_MSG(work != NULL);

	k_spinlock_key_t key = k_spin_lock(&lock);

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, submit_to_queue, queue, work);

	int ret = submit_to_queue_locked(work, &queue);

	k_spin_unlock(&lock, key);

	/* If we changed the queue contents (as indicated by a positive ret)
	 * the queue thread may now be ready, but we missed the reschedule
	 * point because the lock was held.  If this is being invoked by a
	 * preemptible thread then yield.
	 */
	if ((ret > 0) && (k_is_preempt_thread() != 0)) {
		k_yield();
	}

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, submit_to_queue, queue, work, ret);

	return ret;
}

int k_work_submit(struct k_work *work)
{
	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, submit, work);

	int ret = k_work_submit_to_queue(&k_sys_work_q, work);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, submit, work, ret);

	return ret;
}

/* Flush the work item if necessary.
 *
 * Flushing is necessary only if the work is either queued or running.
 *
 * Invoked with work lock held by key.
 * Sleeps.
 *
 * @param work the work item that is to be flushed
 * @param flusher state used to synchronize the flush
 *
 * @retval true if work is queued or running.  If this happens the
 * caller must take the flusher semaphore after releasing the lock.
 *
 * @retval false otherwise.  No wait required.
 */
static bool work_flush_locked(struct k_work *work,
			      struct z_work_flusher *flusher)
{
	bool need_flush = (flags_get(&work->flags)
			   & (K_WORK_QUEUED | K_WORK_RUNNING)) != 0U;

	if (need_flush) {
		struct k_work_q *queue = work->queue;

		__ASSERT_NO_MSG(queue != NULL);

		queue_flusher_locked(queue, work, flusher);
		notify_queue_locked(queue);
	}

	return need_flush;
}

bool k_work_flush(struct k_work *work,
		  struct k_work_sync *sync)
{
	__ASSERT_NO_MSG(work != NULL);
	__ASSERT_NO_MSG(!flag_test(&work->flags, K_WORK_DELAYABLE_BIT));
	__ASSERT_NO_MSG(!k_is_in_isr());
	__ASSERT_NO_MSG(sync != NULL);
#ifdef CONFIG_KERNEL_COHERENCE
	__ASSERT_NO_MSG(arch_mem_coherent(sync));
#endif

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, flush, work);

	struct z_work_flusher *flusher = &sync->flusher;
	k_spinlock_key_t key = k_spin_lock(&lock);

	bool need_flush = work_flush_locked(work, flusher);

	k_spin_unlock(&lock, key);

	/* If necessary wait until the flusher item completes */
	if (need_flush) {
		SYS_PORT_TRACING_OBJ_FUNC_BLOCKING(k_work, flush, work, K_FOREVER);

		k_sem_take(&flusher->sem, K_FOREVER);
	}

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, flush, work, need_flush);

	return need_flush;
}

/* Execute the non-waiting steps necessary to cancel a work item.
 *
 * Invoked with work lock held.
 *
 * @param work the work item to be canceled.
 *
 * @retval true if we need to wait for the work item to finish canceling
 * @retval false if the work item is idle
 *
 * @return k_busy_wait() captured under lock
 */
static int cancel_async_locked(struct k_work *work)
{
	/* If we haven't already started canceling, do it now. */
	if (!flag_test(&work->flags, K_WORK_CANCELING_BIT)) {
		/* Remove it from the queue, if it's queued. */
		queue_remove_locked(work->queue, work);
	}

	/* If it's still busy after it's been dequeued, then flag it
	 * as canceling.
	 */
	int ret = work_busy_get_locked(work);

	if (ret != 0) {
		flag_set(&work->flags, K_WORK_CANCELING_BIT);
		ret = work_busy_get_locked(work);
	}

	return ret;
}

/* Complete cancellation necessary, release work lock, and wait if
 * necessary.
 *
 * Invoked with work lock held by key.
 * Sleeps.
 *
 * @param work work that is being canceled
 * @param canceller state used to synchronize the cancellation
 * @param key used by work lock
 *
 * @retval true if and only if the work was still active on entry.  The caller
 * must wait on the canceller semaphore after releasing the lock.
 *
 * @retval false if work was idle on entry.  The caller need not wait.
 */
static bool cancel_sync_locked(struct k_work *work,
			       struct z_work_canceller *canceller)
{
	bool ret = flag_test(&work->flags, K_WORK_CANCELING_BIT);

	/* If something's still running then we have to wait for
	 * completion, which is indicated when finish_cancel() gets
	 * invoked.
	 */
	if (ret) {
		init_work_cancel(canceller, work);
	}

	return ret;
}

int k_work_cancel(struct k_work *work)
{
	__ASSERT_NO_MSG(work != NULL);
	__ASSERT_NO_MSG(!flag_test(&work->flags, K_WORK_DELAYABLE_BIT));

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, cancel, work);

	k_spinlock_key_t key = k_spin_lock(&lock);
	int ret = cancel_async_locked(work);

	k_spin_unlock(&lock, key);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, cancel, work, ret);

	return ret;
}

bool k_work_cancel_sync(struct k_work *work,
			struct k_work_sync *sync)
{
	__ASSERT_NO_MSG(work != NULL);
	__ASSERT_NO_MSG(sync != NULL);
	__ASSERT_NO_MSG(!flag_test(&work->flags, K_WORK_DELAYABLE_BIT));
	__ASSERT_NO_MSG(!k_is_in_isr());
#ifdef CONFIG_KERNEL_COHERENCE
	__ASSERT_NO_MSG(arch_mem_coherent(sync));
#endif

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, cancel_sync, work, sync);

	struct z_work_canceller *canceller = &sync->canceller;
	k_spinlock_key_t key = k_spin_lock(&lock);
	bool pending = (work_busy_get_locked(work) != 0U);
	bool need_wait = false;

	if (pending) {
		(void)cancel_async_locked(work);
		need_wait = cancel_sync_locked(work, canceller);
	}

	k_spin_unlock(&lock, key);

	if (need_wait) {
		SYS_PORT_TRACING_OBJ_FUNC_BLOCKING(k_work, cancel_sync, work, sync);

		k_sem_take(&canceller->sem, K_FOREVER);
	}

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, cancel_sync, work, sync, pending);
	return pending;
}

/* Loop executed by a work queue thread.
 *
 * @param workq_ptr pointer to the work queue structure
 */
static void work_queue_main(void *workq_ptr, void *p2, void *p3)
{
	struct k_work_q *queue = (struct k_work_q *)workq_ptr;

	while (true) {
		sys_snode_t *node;
		struct k_work *work = NULL;
		k_work_handler_t handler = NULL;
		k_spinlock_key_t key = k_spin_lock(&lock);

		/* Check for and prepare any new work. */
		node = sys_slist_get(&queue->pending);
		if (node != NULL) {
			/* Mark that there's some work active that's
			 * not on the pending list.
			 */
			flag_set(&queue->flags, K_WORK_QUEUE_BUSY_BIT);
			work = CONTAINER_OF(node, struct k_work, node);
			flag_set(&work->flags, K_WORK_RUNNING_BIT);
			flag_clear(&work->flags, K_WORK_QUEUED_BIT);
			handler = work->handler;
		} else if (flag_test_and_clear(&queue->flags,
					       K_WORK_QUEUE_DRAIN_BIT)) {
			/* Not busy and draining: move threads waiting for
			 * drain to ready state.  The held spinlock inhibits
			 * immediate reschedule; released threads get their
			 * chance when this invokes z_sched_wait() below.
			 *
			 * We don't touch K_WORK_QUEUE_PLUGGABLE, so getting
			 * here doesn't mean that the queue will allow new
			 * submissions.
			 */
			(void)z_sched_wake_all(&queue->drainq, 1, NULL);
		} else {
			/* No work is available and no queue state requires
			 * special handling.
			 */
			;
		}

		if (work == NULL) {
			/* Nothing's had a chance to add work since we took
			 * the lock, and we didn't find work nor got asked to
			 * stop.  Just go to sleep: when something happens the
			 * work thread will be woken and we can check again.
			 */

			(void)z_sched_wait(&lock, key, &queue->notifyq,
					   K_FOREVER, NULL);
			continue;
		}

		k_spin_unlock(&lock, key);

		if (work != NULL) {
			bool yield;

			__ASSERT_NO_MSG(handler != NULL);
			handler(work);

			/* Mark the work item as no longer running and deal
			 * with any cancellation issued while it was running.
			 * Clear the BUSY flag and optionally yield to prevent
			 * starving other threads.
			 */
			key = k_spin_lock(&lock);

			flag_clear(&work->flags, K_WORK_RUNNING_BIT);
			if (flag_test(&work->flags, K_WORK_CANCELING_BIT)) {
				finalize_cancel_locked(work);
			}

			flag_clear(&queue->flags, K_WORK_QUEUE_BUSY_BIT);
			yield = !flag_test(&queue->flags, K_WORK_QUEUE_NO_YIELD_BIT);
			k_spin_unlock(&lock, key);

			/* Optionally yield to prevent the work queue from
			 * starving other threads.
			 */
			if (yield) {
				k_yield();
			}
		}
	}
}

void k_work_queue_start(struct k_work_q *queue,
			k_thread_stack_t *stack,
			size_t stack_size,
			int prio,
			const struct k_work_queue_config *cfg)
{
	__ASSERT_NO_MSG(queue);
	__ASSERT_NO_MSG(stack);
	__ASSERT_NO_MSG(!flag_test(&queue->flags, K_WORK_QUEUE_STARTED_BIT));
	uint32_t flags = K_WORK_QUEUE_STARTED;

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work_queue, start, queue);

	sys_slist_init(&queue->pending);
	z_waitq_init(&queue->notifyq);
	z_waitq_init(&queue->drainq);

	if ((cfg != NULL) && cfg->no_yield) {
		flags |= K_WORK_QUEUE_NO_YIELD;
	}

	/* It hasn't actually been started yet, but all the state is in place
	 * so we can submit things and once the thread gets control it's ready
	 * to roll.
	 */
	flags_set(&queue->flags, flags);

	(void)k_thread_create(&queue->thread, stack, stack_size,
			      work_queue_main, queue, NULL, NULL,
			      prio, 0, K_FOREVER);

	if ((cfg != NULL) && (cfg->name != NULL)) {
		k_thread_name_set(&queue->thread, cfg->name);
	}

	k_thread_start(&queue->thread);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work_queue, start, queue);
}

int k_work_queue_drain(struct k_work_q *queue,
		       bool plug)
{
	__ASSERT_NO_MSG(queue);
	__ASSERT_NO_MSG(!k_is_in_isr());

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work_queue, drain, queue);

	int ret = 0;
	k_spinlock_key_t key = k_spin_lock(&lock);

	if (((flags_get(&queue->flags)
	      & (K_WORK_QUEUE_BUSY | K_WORK_QUEUE_DRAIN)) != 0U)
	    || plug
	    || !sys_slist_is_empty(&queue->pending)) {
		flag_set(&queue->flags, K_WORK_QUEUE_DRAIN_BIT);
		if (plug) {
			flag_set(&queue->flags, K_WORK_QUEUE_PLUGGED_BIT);
		}

		notify_queue_locked(queue);
		ret = z_sched_wait(&lock, key, &queue->drainq,
				   K_FOREVER, NULL);
	} else {
		k_spin_unlock(&lock, key);
	}

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work_queue, drain, queue, ret);

	return ret;
}

int k_work_queue_unplug(struct k_work_q *queue)
{
	__ASSERT_NO_MSG(queue);

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work_queue, unplug, queue);

	int ret = -EALREADY;
	k_spinlock_key_t key = k_spin_lock(&lock);

	if (flag_test_and_clear(&queue->flags, K_WORK_QUEUE_PLUGGED_BIT)) {
		ret = 0;
	}

	k_spin_unlock(&lock, key);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work_queue, unplug, queue, ret);

	return ret;
}

#ifdef CONFIG_SYS_CLOCK_EXISTS

/* Timeout handler for delayable work.
 *
 * Invoked by timeout infrastructure.
 * Takes and releases work lock.
 * Conditionally reschedules.
 */
static void work_timeout(struct _timeout *to)
{
	struct k_work_delayable *dw
		= CONTAINER_OF(to, struct k_work_delayable, timeout);
	struct k_work *wp = &dw->work;
	k_spinlock_key_t key = k_spin_lock(&lock);
	struct k_work_q *queue = NULL;

	/* If the work is still marked delayed (should be) then clear that
	 * state and submit it to the queue.  If successful the queue will be
	 * notified of new work at the next reschedule point.
	 *
	 * If not successful there is no notification that the work has been
	 * abandoned.  Sorry.
	 */
	if (flag_test_and_clear(&wp->flags, K_WORK_DELAYED_BIT)) {
		queue = dw->queue;
		(void)submit_to_queue_locked(wp, &queue);
	}

	k_spin_unlock(&lock, key);
}

void k_work_init_delayable(struct k_work_delayable *dwork,
			    k_work_handler_t handler)
{
	__ASSERT_NO_MSG(dwork != NULL);
	__ASSERT_NO_MSG(handler != NULL);

	*dwork = (struct k_work_delayable){
		.work = {
			.handler = handler,
			.flags = K_WORK_DELAYABLE,
		},
	};
	z_init_timeout(&dwork->timeout);

	SYS_PORT_TRACING_OBJ_INIT(k_work_delayable, dwork);
}

static inline int work_delayable_busy_get_locked(const struct k_work_delayable *dwork)
{
	return atomic_get(&dwork->work.flags) & K_WORK_MASK;
}

int k_work_delayable_busy_get(const struct k_work_delayable *dwork)
{
	k_spinlock_key_t key = k_spin_lock(&lock);
	int ret = work_delayable_busy_get_locked(dwork);

	k_spin_unlock(&lock, key);
	return ret;
}

/* Attempt to schedule a work item for future (maybe immediate)
 * submission.
 *
 * Invoked with work lock held.
 *
 * See also submit_to_queue_locked(), which implements this for a no-wait
 * delay.
 *
 * Invoked with work lock held.
 *
 * @param queuep pointer to a pointer to a queue.  On input this
 * should dereference to the proposed queue (which may be null); after
 * completion it will be null if the work was not submitted or if
 * submitted will reference the queue it was submitted to.  That may
 * or may not be the queue provided on input.
 *
 * @param dwork the delayed work structure
 *
 * @param delay the delay to use before scheduling.
 *
 * @retval from submit_to_queue_locked() if delay is K_NO_WAIT; otherwise
 * @retval 1 to indicate successfully scheduled.
 */
static int schedule_for_queue_locked(struct k_work_q **queuep,
				     struct k_work_delayable *dwork,
				     k_timeout_t delay)
{
	int ret = 1;
	struct k_work *work = &dwork->work;

	if (K_TIMEOUT_EQ(delay, K_NO_WAIT)) {
		return submit_to_queue_locked(work, queuep);
	}

	flag_set(&work->flags, K_WORK_DELAYED_BIT);
	dwork->queue = *queuep;

	/* Add timeout */
	z_add_timeout(&dwork->timeout, work_timeout, delay);

	return ret;
}

/* Unschedule delayable work.
 *
 * If the work is delayed, cancel the timeout and clear the delayed
 * flag.
 *
 * Invoked with work lock held.
 *
 * @param dwork pointer to delayable work structure.
 *
 * @return true if and only if work had been delayed so the timeout
 * was cancelled.
 */
static inline bool unschedule_locked(struct k_work_delayable *dwork)
{
	bool ret = false;
	struct k_work *work = &dwork->work;

	/* If scheduled, try to cancel. */
	if (flag_test_and_clear(&work->flags, K_WORK_DELAYED_BIT)) {
		z_abort_timeout(&dwork->timeout);
		ret = true;
	}

	return ret;
}

/* Full cancellation of a delayable work item.
 *
 * Unschedules the delayed part then delegates to standard work
 * cancellation.
 *
 * Invoked with work lock held.
 *
 * @param dwork delayable work item
 *
 * @return k_work_busy_get() flags
 */
static int cancel_delayable_async_locked(struct k_work_delayable *dwork)
{
	(void)unschedule_locked(dwork);

	return cancel_async_locked(&dwork->work);
}

int k_work_schedule_for_queue(struct k_work_q *queue,
			       struct k_work_delayable *dwork,
			       k_timeout_t delay)
{
	__ASSERT_NO_MSG(dwork != NULL);

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, schedule_for_queue, queue, dwork, delay);

	struct k_work *work = &dwork->work;
	int ret = 0;
	k_spinlock_key_t key = k_spin_lock(&lock);

	/* Schedule the work item if it's idle or running. */
	if ((work_busy_get_locked(work) & ~K_WORK_RUNNING) == 0U) {
		ret = schedule_for_queue_locked(&queue, dwork, delay);
	}

	k_spin_unlock(&lock, key);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, schedule_for_queue, queue, dwork, delay, ret);

	return ret;
}

int k_work_schedule(struct k_work_delayable *dwork,
				   k_timeout_t delay)
{
	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, schedule, dwork, delay);

	int ret = k_work_schedule_for_queue(&k_sys_work_q, dwork, delay);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, schedule, dwork, delay, ret);

	return ret;
}

int k_work_reschedule_for_queue(struct k_work_q *queue,
				 struct k_work_delayable *dwork,
				 k_timeout_t delay)
{
	__ASSERT_NO_MSG(dwork != NULL);

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, reschedule_for_queue, queue, dwork, delay);

	int ret = 0;
	k_spinlock_key_t key = k_spin_lock(&lock);

	/* Remove any active scheduling. */
	(void)unschedule_locked(dwork);

	/* Schedule the work item with the new parameters. */
	ret = schedule_for_queue_locked(&queue, dwork, delay);

	k_spin_unlock(&lock, key);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, reschedule_for_queue, queue, dwork, delay, ret);

	return ret;
}

int k_work_reschedule(struct k_work_delayable *dwork,
				     k_timeout_t delay)
{
	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, reschedule, dwork, delay);

	int ret = k_work_reschedule_for_queue(&k_sys_work_q, dwork, delay);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, reschedule, dwork, delay, ret);

	return ret;
}

int k_work_cancel_delayable(struct k_work_delayable *dwork)
{
	__ASSERT_NO_MSG(dwork != NULL);

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, cancel_delayable, dwork);

	k_spinlock_key_t key = k_spin_lock(&lock);
	int ret = cancel_delayable_async_locked(dwork);

	k_spin_unlock(&lock, key);

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, cancel_delayable, dwork, ret);

	return ret;
}

bool k_work_cancel_delayable_sync(struct k_work_delayable *dwork,
				  struct k_work_sync *sync)
{
	__ASSERT_NO_MSG(dwork != NULL);
	__ASSERT_NO_MSG(sync != NULL);
	__ASSERT_NO_MSG(!k_is_in_isr());
#ifdef CONFIG_KERNEL_COHERENCE
	__ASSERT_NO_MSG(arch_mem_coherent(sync));
#endif

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, cancel_delayable_sync, dwork, sync);

	struct z_work_canceller *canceller = &sync->canceller;
	k_spinlock_key_t key = k_spin_lock(&lock);
	bool pending = (work_delayable_busy_get_locked(dwork) != 0U);
	bool need_wait = false;

	if (pending) {
		(void)cancel_delayable_async_locked(dwork);
		need_wait = cancel_sync_locked(&dwork->work, canceller);
	}

	k_spin_unlock(&lock, key);

	if (need_wait) {
		k_sem_take(&canceller->sem, K_FOREVER);
	}

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, cancel_delayable_sync, dwork, sync, pending);
	return pending;
}

bool k_work_flush_delayable(struct k_work_delayable *dwork,
			    struct k_work_sync *sync)
{
	__ASSERT_NO_MSG(dwork != NULL);
	__ASSERT_NO_MSG(sync != NULL);
	__ASSERT_NO_MSG(!k_is_in_isr());
#ifdef CONFIG_KERNEL_COHERENCE
	__ASSERT_NO_MSG(arch_mem_coherent(sync));
#endif

	SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_work, flush_delayable, dwork, sync);

	struct k_work *work = &dwork->work;
	struct z_work_flusher *flusher = &sync->flusher;
	k_spinlock_key_t key = k_spin_lock(&lock);

	/* If it's idle release the lock and return immediately. */
	if (work_busy_get_locked(work) == 0U) {
		k_spin_unlock(&lock, key);

		SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, flush_delayable, dwork, sync, false);

		return false;
	}

	/* If unscheduling did something then submit it.  Ignore a
	 * failed submission (e.g. when cancelling).
	 */
	if (unschedule_locked(dwork)) {
		struct k_work_q *queue = dwork->queue;

		(void)submit_to_queue_locked(work, &queue);
	}

	/* Wait for it to finish */
	bool need_flush = work_flush_locked(work, flusher);

	k_spin_unlock(&lock, key);

	/* If necessary wait until the flusher item completes */
	if (need_flush) {
		k_sem_take(&flusher->sem, K_FOREVER);
	}

	SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_work, flush_delayable, dwork, sync, need_flush);

	return need_flush;
}

#endif /* CONFIG_SYS_CLOCK_EXISTS */