aboutsummaryrefslogtreecommitdiff
path: root/drivers/misc/sgi-xp/xpc_channel.c
blob: 55182c8dd32a232258577347ff2792491c0e3be8 (plain)
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
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2004-2008 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * Cross Partition Communication (XPC) channel support.
 *
 *	This is the part of XPC that manages the channels and
 *	sends/receives messages across them to/from other partitions.
 *
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/completion.h>
#include <asm/sn/sn_sal.h>
#include "xpc.h"

/*
 * Guarantee that the kzalloc'd memory is cacheline aligned.
 */
void *
xpc_kzalloc_cacheline_aligned(size_t size, gfp_t flags, void **base)
{
	/* see if kzalloc will give us cachline aligned memory by default */
	*base = kzalloc(size, flags);
	if (*base == NULL)
		return NULL;

	if ((u64)*base == L1_CACHE_ALIGN((u64)*base))
		return *base;

	kfree(*base);

	/* nope, we'll have to do it ourselves */
	*base = kzalloc(size + L1_CACHE_BYTES, flags);
	if (*base == NULL)
		return NULL;

	return (void *)L1_CACHE_ALIGN((u64)*base);
}

/*
 * Allocate the local message queue and the notify queue.
 */
static enum xp_retval
xpc_allocate_local_msgqueue(struct xpc_channel *ch)
{
	unsigned long irq_flags;
	int nentries;
	size_t nbytes;

	for (nentries = ch->local_nentries; nentries > 0; nentries--) {

		nbytes = nentries * ch->msg_size;
		ch->local_msgqueue = xpc_kzalloc_cacheline_aligned(nbytes,
								   GFP_KERNEL,
						      &ch->local_msgqueue_base);
		if (ch->local_msgqueue == NULL)
			continue;

		nbytes = nentries * sizeof(struct xpc_notify);
		ch->notify_queue = kzalloc(nbytes, GFP_KERNEL);
		if (ch->notify_queue == NULL) {
			kfree(ch->local_msgqueue_base);
			ch->local_msgqueue = NULL;
			continue;
		}

		spin_lock_irqsave(&ch->lock, irq_flags);
		if (nentries < ch->local_nentries) {
			dev_dbg(xpc_chan, "nentries=%d local_nentries=%d, "
				"partid=%d, channel=%d\n", nentries,
				ch->local_nentries, ch->partid, ch->number);

			ch->local_nentries = nentries;
		}
		spin_unlock_irqrestore(&ch->lock, irq_flags);
		return xpSuccess;
	}

	dev_dbg(xpc_chan, "can't get memory for local message queue and notify "
		"queue, partid=%d, channel=%d\n", ch->partid, ch->number);
	return xpNoMemory;
}

/*
 * Allocate the cached remote message queue.
 */
static enum xp_retval
xpc_allocate_remote_msgqueue(struct xpc_channel *ch)
{
	unsigned long irq_flags;
	int nentries;
	size_t nbytes;

	DBUG_ON(ch->remote_nentries <= 0);

	for (nentries = ch->remote_nentries; nentries > 0; nentries--) {

		nbytes = nentries * ch->msg_size;
		ch->remote_msgqueue = xpc_kzalloc_cacheline_aligned(nbytes,
								    GFP_KERNEL,
						     &ch->remote_msgqueue_base);
		if (ch->remote_msgqueue == NULL)
			continue;

		spin_lock_irqsave(&ch->lock, irq_flags);
		if (nentries < ch->remote_nentries) {
			dev_dbg(xpc_chan, "nentries=%d remote_nentries=%d, "
				"partid=%d, channel=%d\n", nentries,
				ch->remote_nentries, ch->partid, ch->number);

			ch->remote_nentries = nentries;
		}
		spin_unlock_irqrestore(&ch->lock, irq_flags);
		return xpSuccess;
	}

	dev_dbg(xpc_chan, "can't get memory for cached remote message queue, "
		"partid=%d, channel=%d\n", ch->partid, ch->number);
	return xpNoMemory;
}

/*
 * Allocate message queues and other stuff associated with a channel.
 *
 * Note: Assumes all of the channel sizes are filled in.
 */
static enum xp_retval
xpc_allocate_msgqueues(struct xpc_channel *ch)
{
	unsigned long irq_flags;
	enum xp_retval ret;

	DBUG_ON(ch->flags & XPC_C_SETUP);

	ret = xpc_allocate_local_msgqueue(ch);
	if (ret != xpSuccess)
		return ret;

	ret = xpc_allocate_remote_msgqueue(ch);
	if (ret != xpSuccess) {
		kfree(ch->local_msgqueue_base);
		ch->local_msgqueue = NULL;
		kfree(ch->notify_queue);
		ch->notify_queue = NULL;
		return ret;
	}

	spin_lock_irqsave(&ch->lock, irq_flags);
	ch->flags |= XPC_C_SETUP;
	spin_unlock_irqrestore(&ch->lock, irq_flags);

	return xpSuccess;
}

/*
 * Process a connect message from a remote partition.
 *
 * Note: xpc_process_connect() is expecting to be called with the
 * spin_lock_irqsave held and will leave it locked upon return.
 */
static void
xpc_process_connect(struct xpc_channel *ch, unsigned long *irq_flags)
{
	enum xp_retval ret;

	DBUG_ON(!spin_is_locked(&ch->lock));

	if (!(ch->flags & XPC_C_OPENREQUEST) ||
	    !(ch->flags & XPC_C_ROPENREQUEST)) {
		/* nothing more to do for now */
		return;
	}
	DBUG_ON(!(ch->flags & XPC_C_CONNECTING));

	if (!(ch->flags & XPC_C_SETUP)) {
		spin_unlock_irqrestore(&ch->lock, *irq_flags);
		ret = xpc_allocate_msgqueues(ch);
		spin_lock_irqsave(&ch->lock, *irq_flags);

		if (ret != xpSuccess)
			XPC_DISCONNECT_CHANNEL(ch, ret, irq_flags);

		if (ch->flags & (XPC_C_CONNECTED | XPC_C_DISCONNECTING))
			return;

		DBUG_ON(!(ch->flags & XPC_C_SETUP));
		DBUG_ON(ch->local_msgqueue == NULL);
		DBUG_ON(ch->remote_msgqueue == NULL);
	}

	if (!(ch->flags & XPC_C_OPENREPLY)) {
		ch->flags |= XPC_C_OPENREPLY;
		xpc_IPI_send_openreply(ch, irq_flags);
	}

	if (!(ch->flags & XPC_C_ROPENREPLY))
		return;

	DBUG_ON(ch->remote_msgqueue_pa == 0);

	ch->flags = (XPC_C_CONNECTED | XPC_C_SETUP);	/* clear all else */

	dev_info(xpc_chan, "channel %d to partition %d connected\n",
		 ch->number, ch->partid);

	spin_unlock_irqrestore(&ch->lock, *irq_flags);
	xpc_create_kthreads(ch, 1, 0);
	spin_lock_irqsave(&ch->lock, *irq_flags);
}

/*
 * Notify those who wanted to be notified upon delivery of their message.
 */
static void
xpc_notify_senders(struct xpc_channel *ch, enum xp_retval reason, s64 put)
{
	struct xpc_notify *notify;
	u8 notify_type;
	s64 get = ch->w_remote_GP.get - 1;

	while (++get < put && atomic_read(&ch->n_to_notify) > 0) {

		notify = &ch->notify_queue[get % ch->local_nentries];

		/*
		 * See if the notify entry indicates it was associated with
		 * a message who's sender wants to be notified. It is possible
		 * that it is, but someone else is doing or has done the
		 * notification.
		 */
		notify_type = notify->type;
		if (notify_type == 0 ||
		    cmpxchg(&notify->type, notify_type, 0) != notify_type) {
			continue;
		}

		DBUG_ON(notify_type != XPC_N_CALL);

		atomic_dec(&ch->n_to_notify);

		if (notify->func != NULL) {
			dev_dbg(xpc_chan, "notify->func() called, notify=0x%p, "
				"msg_number=%ld, partid=%d, channel=%d\n",
				(void *)notify, get, ch->partid, ch->number);

			notify->func(reason, ch->partid, ch->number,
				     notify->key);

			dev_dbg(xpc_chan, "notify->func() returned, "
				"notify=0x%p, msg_number=%ld, partid=%d, "
				"channel=%d\n", (void *)notify, get,
				ch->partid, ch->number);
		}
	}
}

/*
 * Free up message queues and other stuff that were allocated for the specified
 * channel.
 *
 * Note: ch->reason and ch->reason_line are left set for debugging purposes,
 * they're cleared when XPC_C_DISCONNECTED is cleared.
 */
static void
xpc_free_msgqueues(struct xpc_channel *ch)
{
	DBUG_ON(!spin_is_locked(&ch->lock));
	DBUG_ON(atomic_read(&ch->n_to_notify) != 0);

	ch->remote_msgqueue_pa = 0;
	ch->func = NULL;
	ch->key = NULL;
	ch->msg_size = 0;
	ch->local_nentries = 0;
	ch->remote_nentries = 0;
	ch->kthreads_assigned_limit = 0;
	ch->kthreads_idle_limit = 0;

	ch->local_GP->get = 0;
	ch->local_GP->put = 0;
	ch->remote_GP.get = 0;
	ch->remote_GP.put = 0;
	ch->w_local_GP.get = 0;
	ch->w_local_GP.put = 0;
	ch->w_remote_GP.get = 0;
	ch->w_remote_GP.put = 0;
	ch->next_msg_to_pull = 0;

	if (ch->flags & XPC_C_SETUP) {
		ch->flags &= ~XPC_C_SETUP;

		dev_dbg(xpc_chan, "ch->flags=0x%x, partid=%d, channel=%d\n",
			ch->flags, ch->partid, ch->number);

		kfree(ch->local_msgqueue_base);
		ch->local_msgqueue = NULL;
		kfree(ch->remote_msgqueue_base);
		ch->remote_msgqueue = NULL;
		kfree(ch->notify_queue);
		ch->notify_queue = NULL;
	}
}

/*
 * spin_lock_irqsave() is expected to be held on entry.
 */
static void
xpc_process_disconnect(struct xpc_channel *ch, unsigned long *irq_flags)
{
	struct xpc_partition *part = &xpc_partitions[ch->partid];
	u32 channel_was_connected = (ch->flags & XPC_C_WASCONNECTED);

	DBUG_ON(!spin_is_locked(&ch->lock));

	if (!(ch->flags & XPC_C_DISCONNECTING))
		return;

	DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));

	/* make sure all activity has settled down first */

	if (atomic_read(&ch->kthreads_assigned) > 0 ||
	    atomic_read(&ch->references) > 0) {
		return;
	}
	DBUG_ON((ch->flags & XPC_C_CONNECTEDCALLOUT_MADE) &&
		!(ch->flags & XPC_C_DISCONNECTINGCALLOUT_MADE));

	if (part->act_state == XPC_P_DEACTIVATING) {
		/* can't proceed until the other side disengages from us */
		if (xpc_partition_engaged(1UL << ch->partid))
			return;

	} else {

		/* as long as the other side is up do the full protocol */

		if (!(ch->flags & XPC_C_RCLOSEREQUEST))
			return;

		if (!(ch->flags & XPC_C_CLOSEREPLY)) {
			ch->flags |= XPC_C_CLOSEREPLY;
			xpc_IPI_send_closereply(ch, irq_flags);
		}

		if (!(ch->flags & XPC_C_RCLOSEREPLY))
			return;
	}

	/* wake those waiting for notify completion */
	if (atomic_read(&ch->n_to_notify) > 0) {
		/* >>> we do callout while holding ch->lock */
		xpc_notify_senders(ch, ch->reason, ch->w_local_GP.put);
	}

	/* both sides are disconnected now */

	if (ch->flags & XPC_C_DISCONNECTINGCALLOUT_MADE) {
		spin_unlock_irqrestore(&ch->lock, *irq_flags);
		xpc_disconnect_callout(ch, xpDisconnected);
		spin_lock_irqsave(&ch->lock, *irq_flags);
	}

	/* it's now safe to free the channel's message queues */
	xpc_free_msgqueues(ch);

	/* mark disconnected, clear all other flags except XPC_C_WDISCONNECT */
	ch->flags = (XPC_C_DISCONNECTED | (ch->flags & XPC_C_WDISCONNECT));

	atomic_dec(&part->nchannels_active);

	if (channel_was_connected) {
		dev_info(xpc_chan, "channel %d to partition %d disconnected, "
			 "reason=%d\n", ch->number, ch->partid, ch->reason);
	}

	if (ch->flags & XPC_C_WDISCONNECT) {
		/* we won't lose the CPU since we're holding ch->lock */
		complete(&ch->wdisconnect_wait);
	} else if (ch->delayed_IPI_flags) {
		if (part->act_state != XPC_P_DEACTIVATING) {
			/* time to take action on any delayed IPI flags */
			spin_lock(&part->IPI_lock);
			XPC_SET_IPI_FLAGS(part->local_IPI_amo, ch->number,
					  ch->delayed_IPI_flags);
			spin_unlock(&part->IPI_lock);
		}
		ch->delayed_IPI_flags = 0;
	}
}

/*
 * Process a change in the channel's remote connection state.
 */
static void
xpc_process_openclose_IPI(struct xpc_partition *part, int ch_number,
			  u8 IPI_flags)
{
	unsigned long irq_flags;
	struct xpc_openclose_args *args =
	    &part->remote_openclose_args[ch_number];
	struct xpc_channel *ch = &part->channels[ch_number];
	enum xp_retval reason;

	spin_lock_irqsave(&ch->lock, irq_flags);

again:

	if ((ch->flags & XPC_C_DISCONNECTED) &&
	    (ch->flags & XPC_C_WDISCONNECT)) {
		/*
		 * Delay processing IPI flags until thread waiting disconnect
		 * has had a chance to see that the channel is disconnected.
		 */
		ch->delayed_IPI_flags |= IPI_flags;
		spin_unlock_irqrestore(&ch->lock, irq_flags);
		return;
	}

	if (IPI_flags & XPC_IPI_CLOSEREQUEST) {

		dev_dbg(xpc_chan, "XPC_IPI_CLOSEREQUEST (reason=%d) received "
			"from partid=%d, channel=%d\n", args->reason,
			ch->partid, ch->number);

		/*
		 * If RCLOSEREQUEST is set, we're probably waiting for
		 * RCLOSEREPLY. We should find it and a ROPENREQUEST packed
		 * with this RCLOSEREQUEST in the IPI_flags.
		 */

		if (ch->flags & XPC_C_RCLOSEREQUEST) {
			DBUG_ON(!(ch->flags & XPC_C_DISCONNECTING));
			DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));
			DBUG_ON(!(ch->flags & XPC_C_CLOSEREPLY));
			DBUG_ON(ch->flags & XPC_C_RCLOSEREPLY);

			DBUG_ON(!(IPI_flags & XPC_IPI_CLOSEREPLY));
			IPI_flags &= ~XPC_IPI_CLOSEREPLY;
			ch->flags |= XPC_C_RCLOSEREPLY;

			/* both sides have finished disconnecting */
			xpc_process_disconnect(ch, &irq_flags);
			DBUG_ON(!(ch->flags & XPC_C_DISCONNECTED));
			goto again;
		}

		if (ch->flags & XPC_C_DISCONNECTED) {
			if (!(IPI_flags & XPC_IPI_OPENREQUEST)) {
				if ((XPC_GET_IPI_FLAGS(part->local_IPI_amo,
						       ch_number) &
				     XPC_IPI_OPENREQUEST)) {

					DBUG_ON(ch->delayed_IPI_flags != 0);
					spin_lock(&part->IPI_lock);
					XPC_SET_IPI_FLAGS(part->local_IPI_amo,
							  ch_number,
							  XPC_IPI_CLOSEREQUEST);
					spin_unlock(&part->IPI_lock);
				}
				spin_unlock_irqrestore(&ch->lock, irq_flags);
				return;
			}

			XPC_SET_REASON(ch, 0, 0);
			ch->flags &= ~XPC_C_DISCONNECTED;

			atomic_inc(&part->nchannels_active);
			ch->flags |= (XPC_C_CONNECTING | XPC_C_ROPENREQUEST);
		}

		IPI_flags &= ~(XPC_IPI_OPENREQUEST | XPC_IPI_OPENREPLY);

		/*
		 * The meaningful CLOSEREQUEST connection state fields are:
		 *      reason = reason connection is to be closed
		 */

		ch->flags |= XPC_C_RCLOSEREQUEST;

		if (!(ch->flags & XPC_C_DISCONNECTING)) {
			reason = args->reason;
			if (reason <= xpSuccess || reason > xpUnknownReason)
				reason = xpUnknownReason;
			else if (reason == xpUnregistering)
				reason = xpOtherUnregistering;

			XPC_DISCONNECT_CHANNEL(ch, reason, &irq_flags);

			DBUG_ON(IPI_flags & XPC_IPI_CLOSEREPLY);
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}

		xpc_process_disconnect(ch, &irq_flags);
	}

	if (IPI_flags & XPC_IPI_CLOSEREPLY) {

		dev_dbg(xpc_chan, "XPC_IPI_CLOSEREPLY received from partid=%d,"
			" channel=%d\n", ch->partid, ch->number);

		if (ch->flags & XPC_C_DISCONNECTED) {
			DBUG_ON(part->act_state != XPC_P_DEACTIVATING);
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}

		DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));

		if (!(ch->flags & XPC_C_RCLOSEREQUEST)) {
			if ((XPC_GET_IPI_FLAGS(part->local_IPI_amo, ch_number)
			     & XPC_IPI_CLOSEREQUEST)) {

				DBUG_ON(ch->delayed_IPI_flags != 0);
				spin_lock(&part->IPI_lock);
				XPC_SET_IPI_FLAGS(part->local_IPI_amo,
						  ch_number,
						  XPC_IPI_CLOSEREPLY);
				spin_unlock(&part->IPI_lock);
			}
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}

		ch->flags |= XPC_C_RCLOSEREPLY;

		if (ch->flags & XPC_C_CLOSEREPLY) {
			/* both sides have finished disconnecting */
			xpc_process_disconnect(ch, &irq_flags);
		}
	}

	if (IPI_flags & XPC_IPI_OPENREQUEST) {

		dev_dbg(xpc_chan, "XPC_IPI_OPENREQUEST (msg_size=%d, "
			"local_nentries=%d) received from partid=%d, "
			"channel=%d\n", args->msg_size, args->local_nentries,
			ch->partid, ch->number);

		if (part->act_state == XPC_P_DEACTIVATING ||
		    (ch->flags & XPC_C_ROPENREQUEST)) {
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}

		if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_WDISCONNECT)) {
			ch->delayed_IPI_flags |= XPC_IPI_OPENREQUEST;
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}
		DBUG_ON(!(ch->flags & (XPC_C_DISCONNECTED |
				       XPC_C_OPENREQUEST)));
		DBUG_ON(ch->flags & (XPC_C_ROPENREQUEST | XPC_C_ROPENREPLY |
				     XPC_C_OPENREPLY | XPC_C_CONNECTED));

		/*
		 * The meaningful OPENREQUEST connection state fields are:
		 *      msg_size = size of channel's messages in bytes
		 *      local_nentries = remote partition's local_nentries
		 */
		if (args->msg_size == 0 || args->local_nentries == 0) {
			/* assume OPENREQUEST was delayed by mistake */
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}

		ch->flags |= (XPC_C_ROPENREQUEST | XPC_C_CONNECTING);
		ch->remote_nentries = args->local_nentries;

		if (ch->flags & XPC_C_OPENREQUEST) {
			if (args->msg_size != ch->msg_size) {
				XPC_DISCONNECT_CHANNEL(ch, xpUnequalMsgSizes,
						       &irq_flags);
				spin_unlock_irqrestore(&ch->lock, irq_flags);
				return;
			}
		} else {
			ch->msg_size = args->msg_size;

			XPC_SET_REASON(ch, 0, 0);
			ch->flags &= ~XPC_C_DISCONNECTED;

			atomic_inc(&part->nchannels_active);
		}

		xpc_process_connect(ch, &irq_flags);
	}

	if (IPI_flags & XPC_IPI_OPENREPLY) {

		dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY (local_msgqueue_pa=0x%lx, "
			"local_nentries=%d, remote_nentries=%d) received from "
			"partid=%d, channel=%d\n", args->local_msgqueue_pa,
			args->local_nentries, args->remote_nentries,
			ch->partid, ch->number);

		if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_DISCONNECTED)) {
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}
		if (!(ch->flags & XPC_C_OPENREQUEST)) {
			XPC_DISCONNECT_CHANNEL(ch, xpOpenCloseError,
					       &irq_flags);
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return;
		}

		DBUG_ON(!(ch->flags & XPC_C_ROPENREQUEST));
		DBUG_ON(ch->flags & XPC_C_CONNECTED);

		/*
		 * The meaningful OPENREPLY connection state fields are:
		 *      local_msgqueue_pa = physical address of remote
		 *                          partition's local_msgqueue
		 *      local_nentries = remote partition's local_nentries
		 *      remote_nentries = remote partition's remote_nentries
		 */
		DBUG_ON(args->local_msgqueue_pa == 0);
		DBUG_ON(args->local_nentries == 0);
		DBUG_ON(args->remote_nentries == 0);

		ch->flags |= XPC_C_ROPENREPLY;
		ch->remote_msgqueue_pa = args->local_msgqueue_pa;

		if (args->local_nentries < ch->remote_nentries) {
			dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY: new "
				"remote_nentries=%d, old remote_nentries=%d, "
				"partid=%d, channel=%d\n",
				args->local_nentries, ch->remote_nentries,
				ch->partid, ch->number);

			ch->remote_nentries = args->local_nentries;
		}
		if (args->remote_nentries < ch->local_nentries) {
			dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY: new "
				"local_nentries=%d, old local_nentries=%d, "
				"partid=%d, channel=%d\n",
				args->remote_nentries, ch->local_nentries,
				ch->partid, ch->number);

			ch->local_nentries = args->remote_nentries;
		}

		xpc_process_connect(ch, &irq_flags);
	}

	spin_unlock_irqrestore(&ch->lock, irq_flags);
}

/*
 * Attempt to establish a channel connection to a remote partition.
 */
static enum xp_retval
xpc_connect_channel(struct xpc_channel *ch)
{
	unsigned long irq_flags;
	struct xpc_registration *registration = &xpc_registrations[ch->number];

	if (mutex_trylock(&registration->mutex) == 0)
		return xpRetry;

	if (!XPC_CHANNEL_REGISTERED(ch->number)) {
		mutex_unlock(&registration->mutex);
		return xpUnregistered;
	}

	spin_lock_irqsave(&ch->lock, irq_flags);

	DBUG_ON(ch->flags & XPC_C_CONNECTED);
	DBUG_ON(ch->flags & XPC_C_OPENREQUEST);

	if (ch->flags & XPC_C_DISCONNECTING) {
		spin_unlock_irqrestore(&ch->lock, irq_flags);
		mutex_unlock(&registration->mutex);
		return ch->reason;
	}

	/* add info from the channel connect registration to the channel */

	ch->kthreads_assigned_limit = registration->assigned_limit;
	ch->kthreads_idle_limit = registration->idle_limit;
	DBUG_ON(atomic_read(&ch->kthreads_assigned) != 0);
	DBUG_ON(atomic_read(&ch->kthreads_idle) != 0);
	DBUG_ON(atomic_read(&ch->kthreads_active) != 0);

	ch->func = registration->func;
	DBUG_ON(registration->func == NULL);
	ch->key = registration->key;

	ch->local_nentries = registration->nentries;

	if (ch->flags & XPC_C_ROPENREQUEST) {
		if (registration->msg_size != ch->msg_size) {
			/* the local and remote sides aren't the same */

			/*
			 * Because XPC_DISCONNECT_CHANNEL() can block we're
			 * forced to up the registration sema before we unlock
			 * the channel lock. But that's okay here because we're
			 * done with the part that required the registration
			 * sema. XPC_DISCONNECT_CHANNEL() requires that the
			 * channel lock be locked and will unlock and relock
			 * the channel lock as needed.
			 */
			mutex_unlock(&registration->mutex);
			XPC_DISCONNECT_CHANNEL(ch, xpUnequalMsgSizes,
					       &irq_flags);
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			return xpUnequalMsgSizes;
		}
	} else {
		ch->msg_size = registration->msg_size;

		XPC_SET_REASON(ch, 0, 0);
		ch->flags &= ~XPC_C_DISCONNECTED;

		atomic_inc(&xpc_partitions[ch->partid].nchannels_active);
	}

	mutex_unlock(&registration->mutex);

	/* initiate the connection */

	ch->flags |= (XPC_C_OPENREQUEST | XPC_C_CONNECTING);
	xpc_IPI_send_openrequest(ch, &irq_flags);

	xpc_process_connect(ch, &irq_flags);

	spin_unlock_irqrestore(&ch->lock, irq_flags);

	return xpSuccess;
}

/*
 * Clear some of the msg flags in the local message queue.
 */
static inline void
xpc_clear_local_msgqueue_flags(struct xpc_channel *ch)
{
	struct xpc_msg *msg;
	s64 get;

	get = ch->w_remote_GP.get;
	do {
		msg = (struct xpc_msg *)((u64)ch->local_msgqueue +
					 (get % ch->local_nentries) *
					 ch->msg_size);
		msg->flags = 0;
	} while (++get < ch->remote_GP.get);
}

/*
 * Clear some of the msg flags in the remote message queue.
 */
static inline void
xpc_clear_remote_msgqueue_flags(struct xpc_channel *ch)
{
	struct xpc_msg *msg;
	s64 put;

	put = ch->w_remote_GP.put;
	do {
		msg = (struct xpc_msg *)((u64)ch->remote_msgqueue +
					 (put % ch->remote_nentries) *
					 ch->msg_size);
		msg->flags = 0;
	} while (++put < ch->remote_GP.put);
}

static void
xpc_process_msg_IPI(struct xpc_partition *part, int ch_number)
{
	struct xpc_channel *ch = &part->channels[ch_number];
	int nmsgs_sent;

	ch->remote_GP = part->remote_GPs[ch_number];

	/* See what, if anything, has changed for each connected channel */

	xpc_msgqueue_ref(ch);

	if (ch->w_remote_GP.get == ch->remote_GP.get &&
	    ch->w_remote_GP.put == ch->remote_GP.put) {
		/* nothing changed since GPs were last pulled */
		xpc_msgqueue_deref(ch);
		return;
	}

	if (!(ch->flags & XPC_C_CONNECTED)) {
		xpc_msgqueue_deref(ch);
		return;
	}

	/*
	 * First check to see if messages recently sent by us have been
	 * received by the other side. (The remote GET value will have
	 * changed since we last looked at it.)
	 */

	if (ch->w_remote_GP.get != ch->remote_GP.get) {

		/*
		 * We need to notify any senders that want to be notified
		 * that their sent messages have been received by their
		 * intended recipients. We need to do this before updating
		 * w_remote_GP.get so that we don't allocate the same message
		 * queue entries prematurely (see xpc_allocate_msg()).
		 */
		if (atomic_read(&ch->n_to_notify) > 0) {
			/*
			 * Notify senders that messages sent have been
			 * received and delivered by the other side.
			 */
			xpc_notify_senders(ch, xpMsgDelivered,
					   ch->remote_GP.get);
		}

		/*
		 * Clear msg->flags in previously sent messages, so that
		 * they're ready for xpc_allocate_msg().
		 */
		xpc_clear_local_msgqueue_flags(ch);

		ch->w_remote_GP.get = ch->remote_GP.get;

		dev_dbg(xpc_chan, "w_remote_GP.get changed to %ld, partid=%d, "
			"channel=%d\n", ch->w_remote_GP.get, ch->partid,
			ch->number);

		/*
		 * If anyone was waiting for message queue entries to become
		 * available, wake them up.
		 */
		if (atomic_read(&ch->n_on_msg_allocate_wq) > 0)
			wake_up(&ch->msg_allocate_wq);
	}

	/*
	 * Now check for newly sent messages by the other side. (The remote
	 * PUT value will have changed since we last looked at it.)
	 */

	if (ch->w_remote_GP.put != ch->remote_GP.put) {
		/*
		 * Clear msg->flags in previously received messages, so that
		 * they're ready for xpc_get_deliverable_msg().
		 */
		xpc_clear_remote_msgqueue_flags(ch);

		ch->w_remote_GP.put = ch->remote_GP.put;

		dev_dbg(xpc_chan, "w_remote_GP.put changed to %ld, partid=%d, "
			"channel=%d\n", ch->w_remote_GP.put, ch->partid,
			ch->number);

		nmsgs_sent = ch->w_remote_GP.put - ch->w_local_GP.get;
		if (nmsgs_sent > 0) {
			dev_dbg(xpc_chan, "msgs waiting to be copied and "
				"delivered=%d, partid=%d, channel=%d\n",
				nmsgs_sent, ch->partid, ch->number);

			if (ch->flags & XPC_C_CONNECTEDCALLOUT_MADE)
				xpc_activate_kthreads(ch, nmsgs_sent);
		}
	}

	xpc_msgqueue_deref(ch);
}

void
xpc_process_channel_activity(struct xpc_partition *part)
{
	unsigned long irq_flags;
	u64 IPI_amo, IPI_flags;
	struct xpc_channel *ch;
	int ch_number;
	u32 ch_flags;

	IPI_amo = xpc_get_IPI_flags(part);

	/*
	 * Initiate channel connections for registered channels.
	 *
	 * For each connected channel that has pending messages activate idle
	 * kthreads and/or create new kthreads as needed.
	 */

	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
		ch = &part->channels[ch_number];

		/*
		 * Process any open or close related IPI flags, and then deal
		 * with connecting or disconnecting the channel as required.
		 */

		IPI_flags = XPC_GET_IPI_FLAGS(IPI_amo, ch_number);

		if (XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(IPI_flags))
			xpc_process_openclose_IPI(part, ch_number, IPI_flags);

		ch_flags = ch->flags;	/* need an atomic snapshot of flags */

		if (ch_flags & XPC_C_DISCONNECTING) {
			spin_lock_irqsave(&ch->lock, irq_flags);
			xpc_process_disconnect(ch, &irq_flags);
			spin_unlock_irqrestore(&ch->lock, irq_flags);
			continue;
		}

		if (part->act_state == XPC_P_DEACTIVATING)
			continue;

		if (!(ch_flags & XPC_C_CONNECTED)) {
			if (!(ch_flags & XPC_C_OPENREQUEST)) {
				DBUG_ON(ch_flags & XPC_C_SETUP);
				(void)xpc_connect_channel(ch);
			} else {
				spin_lock_irqsave(&ch->lock, irq_flags);
				xpc_process_connect(ch, &irq_flags);
				spin_unlock_irqrestore(&ch->lock, irq_flags);
			}
			continue;
		}

		/*
		 * Process any message related IPI flags, this may involve the
		 * activation of kthreads to deliver any pending messages sent
		 * from the other partition.
		 */

		if (XPC_ANY_MSG_IPI_FLAGS_SET(IPI_flags))
			xpc_process_msg_IPI(part, ch_number);
	}
}

/*
 * XPC's heartbeat code calls this function to inform XPC that a partition is
 * going down.  XPC responds by tearing down the XPartition Communication
 * infrastructure used for the just downed partition.
 *
 * XPC's heartbeat code will never call this function and xpc_partition_up()
 * at the same time. Nor will it ever make multiple calls to either function
 * at the same time.
 */
void
xpc_partition_going_down(struct xpc_partition *part, enum xp_retval reason)
{
	unsigned long irq_flags;
	int ch_number;
	struct xpc_channel *ch;

	dev_dbg(xpc_chan, "deactivating partition %d, reason=%d\n",
		XPC_PARTID(part), reason);

	if (!xpc_part_ref(part)) {
		/* infrastructure for this partition isn't currently set up */
		return;
	}

	/* disconnect channels associated with the partition going down */

	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
		ch = &part->channels[ch_number];

		xpc_msgqueue_ref(ch);
		spin_lock_irqsave(&ch->lock, irq_flags);

		XPC_DISCONNECT_CHANNEL(ch, reason, &irq_flags);

		spin_unlock_irqrestore(&ch->lock, irq_flags);
		xpc_msgqueue_deref(ch);
	}

	xpc_wakeup_channel_mgr(part);

	xpc_part_deref(part);
}

/*
 * Called by XP at the time of channel connection registration to cause
 * XPC to establish connections to all currently active partitions.
 */
void
xpc_initiate_connect(int ch_number)
{
	short partid;
	struct xpc_partition *part;
	struct xpc_channel *ch;

	DBUG_ON(ch_number < 0 || ch_number >= XPC_MAX_NCHANNELS);

	for (partid = 0; partid < xp_max_npartitions; partid++) {
		part = &xpc_partitions[partid];

		if (xpc_part_ref(part)) {
			ch = &part->channels[ch_number];

			/*
			 * Initiate the establishment of a connection on the
			 * newly registered channel to the remote partition.
			 */
			xpc_wakeup_channel_mgr(part);
			xpc_part_deref(part);
		}
	}
}

void
xpc_connected_callout(struct xpc_channel *ch)
{
	/* let the registerer know that a connection has been established */

	if (ch->func != NULL) {
		dev_dbg(xpc_chan, "ch->func() called, reason=xpConnected, "
			"partid=%d, channel=%d\n", ch->partid, ch->number);

		ch->func(xpConnected, ch->partid, ch->number,
			 (void *)(u64)ch->local_nentries, ch->key);

		dev_dbg(xpc_chan, "ch->func() returned, reason=xpConnected, "
			"partid=%d, channel=%d\n", ch->partid, ch->number);
	}
}

/*
 * Called by XP at the time of channel connection unregistration to cause
 * XPC to teardown all current connections for the specified channel.
 *
 * Before returning xpc_initiate_disconnect() will wait until all connections
 * on the specified channel have been closed/torndown. So the caller can be
 * assured that they will not be receiving any more callouts from XPC to the
 * function they registered via xpc_connect().
 *
 * Arguments:
 *
 *	ch_number - channel # to unregister.
 */
void
xpc_initiate_disconnect(int ch_number)
{
	unsigned long irq_flags;
	short partid;
	struct xpc_partition *part;
	struct xpc_channel *ch;

	DBUG_ON(ch_number < 0 || ch_number >= XPC_MAX_NCHANNELS);

	/* initiate the channel disconnect for every active partition */
	for (partid = 0; partid < xp_max_npartitions; partid++) {
		part = &xpc_partitions[partid];

		if (xpc_part_ref(part)) {
			ch = &part->channels[ch_number];
			xpc_msgqueue_ref(ch);

			spin_lock_irqsave(&ch->lock, irq_flags);

			if (!(ch->flags & XPC_C_DISCONNECTED)) {
				ch->flags |= XPC_C_WDISCONNECT;

				XPC_DISCONNECT_CHANNEL(ch, xpUnregistering,
						       &irq_flags);
			}

			spin_unlock_irqrestore(&ch->lock, irq_flags);

			xpc_msgqueue_deref(ch);
			xpc_part_deref(part);
		}
	}

	xpc_disconnect_wait(ch_number);
}

/*
 * To disconnect a channel, and reflect it back to all who may be waiting.
 *
 * An OPEN is not allowed until XPC_C_DISCONNECTING is cleared by
 * xpc_process_disconnect(), and if set, XPC_C_WDISCONNECT is cleared by
 * xpc_disconnect_wait().
 *
 * THE CHANNEL IS TO BE LOCKED BY THE CALLER AND WILL REMAIN LOCKED UPON RETURN.
 */
void
xpc_disconnect_channel(const int line, struct xpc_channel *ch,
		       enum xp_retval reason, unsigned long *irq_flags)
{
	u32 channel_was_connected = (ch->flags & XPC_C_CONNECTED);

	DBUG_ON(!spin_is_locked(&ch->lock));

	if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_DISCONNECTED))
		return;

	DBUG_ON(!(ch->flags & (XPC_C_CONNECTING | XPC_C_CONNECTED)));

	dev_dbg(xpc_chan, "reason=%d, line=%d, partid=%d, channel=%d\n",
		reason, line, ch->partid, ch->number);

	XPC_SET_REASON(ch, reason, line);

	ch->flags |= (XPC_C_CLOSEREQUEST | XPC_C_DISCONNECTING);
	/* some of these may not have been set */
	ch->flags &= ~(XPC_C_OPENREQUEST | XPC_C_OPENREPLY |
		       XPC_C_ROPENREQUEST | XPC_C_ROPENREPLY |
		       XPC_C_CONNECTING | XPC_C_CONNECTED);

	xpc_IPI_send_closerequest(ch, irq_flags);

	if (channel_was_connected)
		ch->flags |= XPC_C_WASCONNECTED;

	spin_unlock_irqrestore(&ch->lock, *irq_flags);

	/* wake all idle kthreads so they can exit */
	if (atomic_read(&ch->kthreads_idle) > 0) {
		wake_up_all(&ch->idle_wq);

	} else if ((ch->flags & XPC_C_CONNECTEDCALLOUT_MADE) &&
		   !(ch->flags & XPC_C_DISCONNECTINGCALLOUT)) {
		/* start a kthread that will do the xpDisconnecting callout */
		xpc_create_kthreads(ch, 1, 1);
	}

	/* wake those waiting to allocate an entry from the local msg queue */
	if (atomic_read(&ch->n_on_msg_allocate_wq) > 0)
		wake_up(&ch->msg_allocate_wq);

	spin_lock_irqsave(&ch->lock, *irq_flags);
}

void
xpc_disconnect_callout(struct xpc_channel *ch, enum xp_retval reason)
{
	/*
	 * Let the channel's registerer know that the channel is being
	 * disconnected. We don't want to do this if the registerer was never
	 * informed of a connection being made.
	 */

	if (ch->func != NULL) {
		dev_dbg(xpc_chan, "ch->func() called, reason=%d, partid=%d, "
			"channel=%d\n", reason, ch->partid, ch->number);

		ch->func(reason, ch->partid, ch->number, NULL, ch->key);

		dev_dbg(xpc_chan, "ch->func() returned, reason=%d, partid=%d, "
			"channel=%d\n", reason, ch->partid, ch->number);
	}
}

/*
 * Wait for a message entry to become available for the specified channel,
 * but don't wait any longer than 1 jiffy.
 */
enum xp_retval
xpc_allocate_msg_wait(struct xpc_channel *ch)
{
	enum xp_retval ret;

	if (ch->flags & XPC_C_DISCONNECTING) {
		DBUG_ON(ch->reason == xpInterrupted);
		return ch->reason;
	}

	atomic_inc(&ch->n_on_msg_allocate_wq);
	ret = interruptible_sleep_on_timeout(&ch->msg_allocate_wq, 1);
	atomic_dec(&ch->n_on_msg_allocate_wq);

	if (ch->flags & XPC_C_DISCONNECTING) {
		ret = ch->reason;
		DBUG_ON(ch->reason == xpInterrupted);
	} else if (ret == 0) {
		ret = xpTimeout;
	} else {
		ret = xpInterrupted;
	}

	return ret;
}

/*
 * Send a message that contains the user's payload on the specified channel
 * connected to the specified partition.
 *
 * NOTE that this routine can sleep waiting for a message entry to become
 * available. To not sleep, pass in the XPC_NOWAIT flag.
 *
 * Once sent, this routine will not wait for the message to be received, nor
 * will notification be given when it does happen.
 *
 * Arguments:
 *
 *	partid - ID of partition to which the channel is connected.
 *	ch_number - channel # to send message on.
 *	flags - see xp.h for valid flags.
 *	payload - pointer to the payload which is to be sent.
 *	payload_size - size of the payload in bytes.
 */
enum xp_retval
xpc_initiate_send(short partid, int ch_number, u32 flags, void *payload,
		  u16 payload_size)
{
	struct xpc_partition *part = &xpc_partitions[partid];
	enum xp_retval ret = xpUnknownReason;

	dev_dbg(xpc_chan, "payload=0x%p, partid=%d, channel=%d\n", payload,
		partid, ch_number);

	DBUG_ON(partid < 0 || partid >= xp_max_npartitions);
	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
	DBUG_ON(payload == NULL);

	if (xpc_part_ref(part)) {
		ret = xpc_send_msg(&part->channels[ch_number], flags, payload,
				   payload_size, 0, NULL, NULL);
		xpc_part_deref(part);
	}

	return ret;
}

/*
 * Send a message that contains the user's payload on the specified channel
 * connected to the specified partition.
 *
 * NOTE that this routine can sleep waiting for a message entry to become
 * available. To not sleep, pass in the XPC_NOWAIT flag.
 *
 * This routine will not wait for the message to be sent or received.
 *
 * Once the remote end of the channel has received the message, the function
 * passed as an argument to xpc_initiate_send_notify() will be called. This
 * allows the sender to free up or re-use any buffers referenced by the
 * message, but does NOT mean the message has been processed at the remote
 * end by a receiver.
 *
 * If this routine returns an error, the caller's function will NOT be called.
 *
 * Arguments:
 *
 *	partid - ID of partition to which the channel is connected.
 *	ch_number - channel # to send message on.
 *	flags - see xp.h for valid flags.
 *	payload - pointer to the payload which is to be sent.
 *	payload_size - size of the payload in bytes.
 *	func - function to call with asynchronous notification of message
 *		  receipt. THIS FUNCTION MUST BE NON-BLOCKING.
 *	key - user-defined key to be passed to the function when it's called.
 */
enum xp_retval
xpc_initiate_send_notify(short partid, int ch_number, u32 flags, void *payload,
			 u16 payload_size, xpc_notify_func func, void *key)
{
	struct xpc_partition *part = &xpc_partitions[partid];
	enum xp_retval ret = xpUnknownReason;

	dev_dbg(xpc_chan, "payload=0x%p, partid=%d, channel=%d\n", payload,
		partid, ch_number);

	DBUG_ON(partid < 0 || partid >= xp_max_npartitions);
	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
	DBUG_ON(payload == NULL);
	DBUG_ON(func == NULL);

	if (xpc_part_ref(part)) {
		ret = xpc_send_msg(&part->channels[ch_number], flags, payload,
				   payload_size, XPC_N_CALL, func, key);
		xpc_part_deref(part);
	}
	return ret;
}

/*
 * Deliver a message to its intended recipient.
 */
void
xpc_deliver_msg(struct xpc_channel *ch)
{
	struct xpc_msg *msg;

	msg = xpc_get_deliverable_msg(ch);
	if (msg != NULL) {

		/*
		 * This ref is taken to protect the payload itself from being
		 * freed before the user is finished with it, which the user
		 * indicates by calling xpc_initiate_received().
		 */
		xpc_msgqueue_ref(ch);

		atomic_inc(&ch->kthreads_active);

		if (ch->func != NULL) {
			dev_dbg(xpc_chan, "ch->func() called, msg=0x%p, "
				"msg_number=%ld, partid=%d, channel=%d\n",
				(void *)msg, msg->number, ch->partid,
				ch->number);

			/* deliver the message to its intended recipient */
			ch->func(xpMsgReceived, ch->partid, ch->number,
				 &msg->payload, ch->key);

			dev_dbg(xpc_chan, "ch->func() returned, msg=0x%p, "
				"msg_number=%ld, partid=%d, channel=%d\n",
				(void *)msg, msg->number, ch->partid,
				ch->number);
		}

		atomic_dec(&ch->kthreads_active);
	}
}

/*
 * Acknowledge receipt of a delivered message.
 *
 * If a message has XPC_M_INTERRUPT set, send an interrupt to the partition
 * that sent the message.
 *
 * This function, although called by users, does not call xpc_part_ref() to
 * ensure that the partition infrastructure is in place. It relies on the
 * fact that we called xpc_msgqueue_ref() in xpc_deliver_msg().
 *
 * Arguments:
 *
 *	partid - ID of partition to which the channel is connected.
 *	ch_number - channel # message received on.
 *	payload - pointer to the payload area allocated via
 *			xpc_initiate_send() or xpc_initiate_send_notify().
 */
void
xpc_initiate_received(short partid, int ch_number, void *payload)
{
	struct xpc_partition *part = &xpc_partitions[partid];
	struct xpc_channel *ch;
	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);

	DBUG_ON(partid < 0 || partid >= xp_max_npartitions);
	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);

	ch = &part->channels[ch_number];
	xpc_received_msg(ch, msg);

	/* the call to xpc_msgqueue_ref() was done by xpc_deliver_msg()  */
	xpc_msgqueue_deref(ch);
}