Home Home > GIT Browse
summaryrefslogtreecommitdiff
blob: efaa5b3f4d3f0dc2faff7c4d8a1a5a5757ed2ff2 (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
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
// SPDX-License-Identifier: GPL-2.0+
/*
 * Read-Copy Update module-based torture test facility
 *
 * Copyright (C) IBM Corporation, 2005, 2006
 *
 * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 *	  Josh Triplett <josh@joshtriplett.org>
 *
 * See also:  Documentation/RCU/torture.txt
 */

#define pr_fmt(fmt) fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/rcupdate.h>
#include <linux/interrupt.h>
#include <linux/sched/signal.h>
#include <uapi/linux/sched/types.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/stat.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/trace_clock.h>
#include <asm/byteorder.h>
#include <linux/torture.h>
#include <linux/vmalloc.h>
#include <linux/sched/debug.h>
#include <linux/sched/sysctl.h>
#include <linux/oom.h>

#include "rcu.h"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");


/* Bits for ->extendables field, extendables param, and related definitions. */
#define RCUTORTURE_RDR_SHIFT	 8	/* Put SRCU index in upper bits. */
#define RCUTORTURE_RDR_MASK	 ((1 << RCUTORTURE_RDR_SHIFT) - 1)
#define RCUTORTURE_RDR_BH	 0x01	/* Extend readers by disabling bh. */
#define RCUTORTURE_RDR_IRQ	 0x02	/*  ... disabling interrupts. */
#define RCUTORTURE_RDR_PREEMPT	 0x04	/*  ... disabling preemption. */
#define RCUTORTURE_RDR_RBH	 0x08	/*  ... rcu_read_lock_bh(). */
#define RCUTORTURE_RDR_SCHED	 0x10	/*  ... rcu_read_lock_sched(). */
#define RCUTORTURE_RDR_RCU	 0x20	/*  ... entering another RCU reader. */
#define RCUTORTURE_RDR_NBITS	 6	/* Number of bits defined above. */
#define RCUTORTURE_MAX_EXTEND	 \
	(RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
	 RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
#define RCUTORTURE_RDR_MAX_LOOPS 0x7	/* Maximum reader extensions. */
					/* Must be power of two minus one. */
#define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3)

torture_param(int, extendables, RCUTORTURE_MAX_EXTEND,
	      "Extend readers by disabling bh (1), irqs (2), or preempt (4)");
torture_param(int, fqs_duration, 0,
	      "Duration of fqs bursts (us), 0 to disable");
torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
torture_param(bool, fwd_progress, 1, "Test grace-period forward progress");
torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
torture_param(int, fwd_progress_holdoff, 60,
	      "Time between forward-progress tests (s)");
torture_param(bool, fwd_progress_need_resched, 1,
	      "Hide cond_resched() behind need_resched()");
torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
torture_param(bool, gp_normal, false,
	     "Use normal (non-expedited) GP wait primitives");
torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
torture_param(int, n_barrier_cbs, 0,
	     "# of callbacks/kthreads for barrier testing");
torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
torture_param(int, nreaders, -1, "Number of RCU reader threads");
torture_param(int, object_debug, 0,
	     "Enable debug-object double call_rcu() testing");
torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
torture_param(int, onoff_interval, 0,
	     "Time between CPU hotplugs (jiffies), 0=disable");
torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
torture_param(int, stall_cpu_holdoff, 10,
	     "Time to wait before starting stall (s).");
torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
torture_param(int, stat_interval, 60,
	     "Number of seconds between stats printk()s");
torture_param(int, stutter, 5, "Number of seconds to run/halt test");
torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
torture_param(int, test_boost_duration, 4,
	     "Duration of each boost test, seconds.");
torture_param(int, test_boost_interval, 7,
	     "Interval between boost tests, seconds.");
torture_param(bool, test_no_idle_hz, true,
	     "Test support for tickless idle CPUs");
torture_param(int, verbose, 1,
	     "Enable verbose debugging printk()s");

static char *torture_type = "rcu";
module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");

static int nrealreaders;
static struct task_struct *writer_task;
static struct task_struct **fakewriter_tasks;
static struct task_struct **reader_tasks;
static struct task_struct *stats_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
static struct task_struct *stall_task;
static struct task_struct *fwd_prog_task;
static struct task_struct **barrier_cbs_tasks;
static struct task_struct *barrier_task;

#define RCU_TORTURE_PIPE_LEN 10

struct rcu_torture {
	struct rcu_head rtort_rcu;
	int rtort_pipe_count;
	struct list_head rtort_free;
	int rtort_mbtest;
};

static LIST_HEAD(rcu_torture_freelist);
static struct rcu_torture __rcu *rcu_torture_current;
static unsigned long rcu_torture_current_version;
static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
static DEFINE_SPINLOCK(rcu_torture_lock);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
static atomic_t n_rcu_torture_alloc;
static atomic_t n_rcu_torture_alloc_fail;
static atomic_t n_rcu_torture_free;
static atomic_t n_rcu_torture_mberror;
static atomic_t n_rcu_torture_error;
static long n_rcu_torture_barrier_error;
static long n_rcu_torture_boost_ktrerror;
static long n_rcu_torture_boost_rterror;
static long n_rcu_torture_boost_failure;
static long n_rcu_torture_boosts;
static atomic_long_t n_rcu_torture_timers;
static long n_barrier_attempts;
static long n_barrier_successes; /* did rcu_barrier test succeed? */
static struct list_head rcu_torture_removed;

static int rcu_torture_writer_state;
#define RTWS_FIXED_DELAY	0
#define RTWS_DELAY		1
#define RTWS_REPLACE		2
#define RTWS_DEF_FREE		3
#define RTWS_EXP_SYNC		4
#define RTWS_COND_GET		5
#define RTWS_COND_SYNC		6
#define RTWS_SYNC		7
#define RTWS_STUTTER		8
#define RTWS_STOPPING		9
static const char * const rcu_torture_writer_state_names[] = {
	"RTWS_FIXED_DELAY",
	"RTWS_DELAY",
	"RTWS_REPLACE",
	"RTWS_DEF_FREE",
	"RTWS_EXP_SYNC",
	"RTWS_COND_GET",
	"RTWS_COND_SYNC",
	"RTWS_SYNC",
	"RTWS_STUTTER",
	"RTWS_STOPPING",
};

/* Record reader segment types and duration for first failing read. */
struct rt_read_seg {
	int rt_readstate;
	unsigned long rt_delay_jiffies;
	unsigned long rt_delay_ms;
	unsigned long rt_delay_us;
	bool rt_preempted;
};
static int err_segs_recorded;
static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
static int rt_read_nsegs;

static const char *rcu_torture_writer_state_getname(void)
{
	unsigned int i = READ_ONCE(rcu_torture_writer_state);

	if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
		return "???";
	return rcu_torture_writer_state_names[i];
}

#if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
#define rcu_can_boost() 1
#else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
#define rcu_can_boost() 0
#endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */

#ifdef CONFIG_RCU_TRACE
static u64 notrace rcu_trace_clock_local(void)
{
	u64 ts = trace_clock_local();

	(void)do_div(ts, NSEC_PER_USEC);
	return ts;
}
#else /* #ifdef CONFIG_RCU_TRACE */
static u64 notrace rcu_trace_clock_local(void)
{
	return 0ULL;
}
#endif /* #else #ifdef CONFIG_RCU_TRACE */

static unsigned long boost_starttime;	/* jiffies of next boost test start. */
static DEFINE_MUTEX(boost_mutex);	/* protect setting boost_starttime */
					/*  and boost task create/destroy. */
static atomic_t barrier_cbs_count;	/* Barrier callbacks registered. */
static bool barrier_phase;		/* Test phase. */
static atomic_t barrier_cbs_invoked;	/* Barrier callbacks invoked. */
static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);

static bool rcu_fwd_cb_nodelay;		/* Short rcu_torture_delay() delays. */

/*
 * Allocate an element from the rcu_tortures pool.
 */
static struct rcu_torture *
rcu_torture_alloc(void)
{
	struct list_head *p;

	spin_lock_bh(&rcu_torture_lock);
	if (list_empty(&rcu_torture_freelist)) {
		atomic_inc(&n_rcu_torture_alloc_fail);
		spin_unlock_bh(&rcu_torture_lock);
		return NULL;
	}
	atomic_inc(&n_rcu_torture_alloc);
	p = rcu_torture_freelist.next;
	list_del_init(p);
	spin_unlock_bh(&rcu_torture_lock);
	return container_of(p, struct rcu_torture, rtort_free);
}

/*
 * Free an element to the rcu_tortures pool.
 */
static void
rcu_torture_free(struct rcu_torture *p)
{
	atomic_inc(&n_rcu_torture_free);
	spin_lock_bh(&rcu_torture_lock);
	list_add_tail(&p->rtort_free, &rcu_torture_freelist);
	spin_unlock_bh(&rcu_torture_lock);
}

/*
 * Operations vector for selecting different types of tests.
 */

struct rcu_torture_ops {
	int ttype;
	void (*init)(void);
	void (*cleanup)(void);
	int (*readlock)(void);
	void (*read_delay)(struct torture_random_state *rrsp,
			   struct rt_read_seg *rtrsp);
	void (*readunlock)(int idx);
	unsigned long (*get_gp_seq)(void);
	unsigned long (*gp_diff)(unsigned long new, unsigned long old);
	void (*deferred_free)(struct rcu_torture *p);
	void (*sync)(void);
	void (*exp_sync)(void);
	unsigned long (*get_state)(void);
	void (*cond_sync)(unsigned long oldstate);
	call_rcu_func_t call;
	void (*cb_barrier)(void);
	void (*fqs)(void);
	void (*stats)(void);
	int (*stall_dur)(void);
	int irq_capable;
	int can_boost;
	int extendables;
	const char *name;
};

static struct rcu_torture_ops *cur_ops;

/*
 * Definitions for rcu torture testing.
 */

static int rcu_torture_read_lock(void) __acquires(RCU)
{
	rcu_read_lock();
	return 0;
}

static void
rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
{
	unsigned long started;
	unsigned long completed;
	const unsigned long shortdelay_us = 200;
	unsigned long longdelay_ms = 300;
	unsigned long long ts;

	/* We want a short delay sometimes to make a reader delay the grace
	 * period, and we want a long delay occasionally to trigger
	 * force_quiescent_state. */

	if (!rcu_fwd_cb_nodelay &&
	    !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
		started = cur_ops->get_gp_seq();
		ts = rcu_trace_clock_local();
		if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
			longdelay_ms = 5; /* Avoid triggering BH limits. */
		mdelay(longdelay_ms);
		rtrsp->rt_delay_ms = longdelay_ms;
		completed = cur_ops->get_gp_seq();
		do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
					  started, completed);
	}
	if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
		udelay(shortdelay_us);
		rtrsp->rt_delay_us = shortdelay_us;
	}
	if (!preempt_count() &&
	    !(torture_random(rrsp) % (nrealreaders * 500))) {
		torture_preempt_schedule();  /* QS only if preemptible. */
		rtrsp->rt_preempted = true;
	}
}

static void rcu_torture_read_unlock(int idx) __releases(RCU)
{
	rcu_read_unlock();
}

/*
 * Update callback in the pipe.  This should be invoked after a grace period.
 */
static bool
rcu_torture_pipe_update_one(struct rcu_torture *rp)
{
	int i;

	i = rp->rtort_pipe_count;
	if (i > RCU_TORTURE_PIPE_LEN)
		i = RCU_TORTURE_PIPE_LEN;
	atomic_inc(&rcu_torture_wcount[i]);
	if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
		rp->rtort_mbtest = 0;
		return true;
	}
	return false;
}

/*
 * Update all callbacks in the pipe.  Suitable for synchronous grace-period
 * primitives.
 */
static void
rcu_torture_pipe_update(struct rcu_torture *old_rp)
{
	struct rcu_torture *rp;
	struct rcu_torture *rp1;

	if (old_rp)
		list_add(&old_rp->rtort_free, &rcu_torture_removed);
	list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
		if (rcu_torture_pipe_update_one(rp)) {
			list_del(&rp->rtort_free);
			rcu_torture_free(rp);
		}
	}
}

static void
rcu_torture_cb(struct rcu_head *p)
{
	struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);

	if (torture_must_stop_irq()) {
		/* Test is ending, just drop callbacks on the floor. */
		/* The next initialization will pick up the pieces. */
		return;
	}
	if (rcu_torture_pipe_update_one(rp))
		rcu_torture_free(rp);
	else
		cur_ops->deferred_free(rp);
}

static unsigned long rcu_no_completed(void)
{
	return 0;
}

static void rcu_torture_deferred_free(struct rcu_torture *p)
{
	call_rcu(&p->rtort_rcu, rcu_torture_cb);
}

static void rcu_sync_torture_init(void)
{
	INIT_LIST_HEAD(&rcu_torture_removed);
}

static struct rcu_torture_ops rcu_ops = {
	.ttype		= RCU_FLAVOR,
	.init		= rcu_sync_torture_init,
	.readlock	= rcu_torture_read_lock,
	.read_delay	= rcu_read_delay,
	.readunlock	= rcu_torture_read_unlock,
	.get_gp_seq	= rcu_get_gp_seq,
	.gp_diff	= rcu_seq_diff,
	.deferred_free	= rcu_torture_deferred_free,
	.sync		= synchronize_rcu,
	.exp_sync	= synchronize_rcu_expedited,
	.get_state	= get_state_synchronize_rcu,
	.cond_sync	= cond_synchronize_rcu,
	.call		= call_rcu,
	.cb_barrier	= rcu_barrier,
	.fqs		= rcu_force_quiescent_state,
	.stats		= NULL,
	.stall_dur	= rcu_jiffies_till_stall_check,
	.irq_capable	= 1,
	.can_boost	= rcu_can_boost(),
	.extendables	= RCUTORTURE_MAX_EXTEND,
	.name		= "rcu"
};

/*
 * Don't even think about trying any of these in real life!!!
 * The names includes "busted", and they really means it!
 * The only purpose of these functions is to provide a buggy RCU
 * implementation to make sure that rcutorture correctly emits
 * buggy-RCU error messages.
 */
static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
{
	/* This is a deliberate bug for testing purposes only! */
	rcu_torture_cb(&p->rtort_rcu);
}

static void synchronize_rcu_busted(void)
{
	/* This is a deliberate bug for testing purposes only! */
}

static void
call_rcu_busted(struct rcu_head *head, rcu_callback_t func)
{
	/* This is a deliberate bug for testing purposes only! */
	func(head);
}

static struct rcu_torture_ops rcu_busted_ops = {
	.ttype		= INVALID_RCU_FLAVOR,
	.init		= rcu_sync_torture_init,
	.readlock	= rcu_torture_read_lock,
	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
	.readunlock	= rcu_torture_read_unlock,
	.get_gp_seq	= rcu_no_completed,
	.deferred_free	= rcu_busted_torture_deferred_free,
	.sync		= synchronize_rcu_busted,
	.exp_sync	= synchronize_rcu_busted,
	.call		= call_rcu_busted,
	.cb_barrier	= NULL,
	.fqs		= NULL,
	.stats		= NULL,
	.irq_capable	= 1,
	.name		= "busted"
};

/*
 * Definitions for srcu torture testing.
 */

DEFINE_STATIC_SRCU(srcu_ctl);
static struct srcu_struct srcu_ctld;
static struct srcu_struct *srcu_ctlp = &srcu_ctl;

static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
{
	return srcu_read_lock(srcu_ctlp);
}

static void
srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
{
	long delay;
	const long uspertick = 1000000 / HZ;
	const long longdelay = 10;

	/* We want there to be long-running readers, but not all the time. */

	delay = torture_random(rrsp) %
		(nrealreaders * 2 * longdelay * uspertick);
	if (!delay && in_task()) {
		schedule_timeout_interruptible(longdelay);
		rtrsp->rt_delay_jiffies = longdelay;
	} else {
		rcu_read_delay(rrsp, rtrsp);
	}
}

static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
{
	srcu_read_unlock(srcu_ctlp, idx);
}

static unsigned long srcu_torture_completed(void)
{
	return srcu_batches_completed(srcu_ctlp);
}

static void srcu_torture_deferred_free(struct rcu_torture *rp)
{
	call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
}

static void srcu_torture_synchronize(void)
{
	synchronize_srcu(srcu_ctlp);
}

static void srcu_torture_call(struct rcu_head *head,
			      rcu_callback_t func)
{
	call_srcu(srcu_ctlp, head, func);
}

static void srcu_torture_barrier(void)
{
	srcu_barrier(srcu_ctlp);
}

static void srcu_torture_stats(void)
{
	srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG);
}

static void srcu_torture_synchronize_expedited(void)
{
	synchronize_srcu_expedited(srcu_ctlp);
}

static struct rcu_torture_ops srcu_ops = {
	.ttype		= SRCU_FLAVOR,
	.init		= rcu_sync_torture_init,
	.readlock	= srcu_torture_read_lock,
	.read_delay	= srcu_read_delay,
	.readunlock	= srcu_torture_read_unlock,
	.get_gp_seq	= srcu_torture_completed,
	.deferred_free	= srcu_torture_deferred_free,
	.sync		= srcu_torture_synchronize,
	.exp_sync	= srcu_torture_synchronize_expedited,
	.call		= srcu_torture_call,
	.cb_barrier	= srcu_torture_barrier,
	.stats		= srcu_torture_stats,
	.irq_capable	= 1,
	.name		= "srcu"
};

static void srcu_torture_init(void)
{
	rcu_sync_torture_init();
	WARN_ON(init_srcu_struct(&srcu_ctld));
	srcu_ctlp = &srcu_ctld;
}

static void srcu_torture_cleanup(void)
{
	cleanup_srcu_struct(&srcu_ctld);
	srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
}

/* As above, but dynamically allocated. */
static struct rcu_torture_ops srcud_ops = {
	.ttype		= SRCU_FLAVOR,
	.init		= srcu_torture_init,
	.cleanup	= srcu_torture_cleanup,
	.readlock	= srcu_torture_read_lock,
	.read_delay	= srcu_read_delay,
	.readunlock	= srcu_torture_read_unlock,
	.get_gp_seq	= srcu_torture_completed,
	.deferred_free	= srcu_torture_deferred_free,
	.sync		= srcu_torture_synchronize,
	.exp_sync	= srcu_torture_synchronize_expedited,
	.call		= srcu_torture_call,
	.cb_barrier	= srcu_torture_barrier,
	.stats		= srcu_torture_stats,
	.irq_capable	= 1,
	.name		= "srcud"
};

/* As above, but broken due to inappropriate reader extension. */
static struct rcu_torture_ops busted_srcud_ops = {
	.ttype		= SRCU_FLAVOR,
	.init		= srcu_torture_init,
	.cleanup	= srcu_torture_cleanup,
	.readlock	= srcu_torture_read_lock,
	.read_delay	= rcu_read_delay,
	.readunlock	= srcu_torture_read_unlock,
	.get_gp_seq	= srcu_torture_completed,
	.deferred_free	= srcu_torture_deferred_free,
	.sync		= srcu_torture_synchronize,
	.exp_sync	= srcu_torture_synchronize_expedited,
	.call		= srcu_torture_call,
	.cb_barrier	= srcu_torture_barrier,
	.stats		= srcu_torture_stats,
	.irq_capable	= 1,
	.extendables	= RCUTORTURE_MAX_EXTEND,
	.name		= "busted_srcud"
};

/*
 * Definitions for RCU-tasks torture testing.
 */

static int tasks_torture_read_lock(void)
{
	return 0;
}

static void tasks_torture_read_unlock(int idx)
{
}

static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
{
	call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
}

static struct rcu_torture_ops tasks_ops = {
	.ttype		= RCU_TASKS_FLAVOR,
	.init		= rcu_sync_torture_init,
	.readlock	= tasks_torture_read_lock,
	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
	.readunlock	= tasks_torture_read_unlock,
	.get_gp_seq	= rcu_no_completed,
	.deferred_free	= rcu_tasks_torture_deferred_free,
	.sync		= synchronize_rcu_tasks,
	.exp_sync	= synchronize_rcu_tasks,
	.call		= call_rcu_tasks,
	.cb_barrier	= rcu_barrier_tasks,
	.fqs		= NULL,
	.stats		= NULL,
	.irq_capable	= 1,
	.name		= "tasks"
};

static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
{
	if (!cur_ops->gp_diff)
		return new - old;
	return cur_ops->gp_diff(new, old);
}

static bool __maybe_unused torturing_tasks(void)
{
	return cur_ops == &tasks_ops;
}

/*
 * RCU torture priority-boost testing.  Runs one real-time thread per
 * CPU for moderate bursts, repeatedly registering RCU callbacks and
 * spinning waiting for them to be invoked.  If a given callback takes
 * too long to be invoked, we assume that priority inversion has occurred.
 */

struct rcu_boost_inflight {
	struct rcu_head rcu;
	int inflight;
};

static void rcu_torture_boost_cb(struct rcu_head *head)
{
	struct rcu_boost_inflight *rbip =
		container_of(head, struct rcu_boost_inflight, rcu);

	/* Ensure RCU-core accesses precede clearing ->inflight */
	smp_store_release(&rbip->inflight, 0);
}

static int old_rt_runtime = -1;

static void rcu_torture_disable_rt_throttle(void)
{
	/*
	 * Disable RT throttling so that rcutorture's boost threads don't get
	 * throttled. Only possible if rcutorture is built-in otherwise the
	 * user should manually do this by setting the sched_rt_period_us and
	 * sched_rt_runtime sysctls.
	 */
	if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
		return;

	old_rt_runtime = sysctl_sched_rt_runtime;
	sysctl_sched_rt_runtime = -1;
}

static void rcu_torture_enable_rt_throttle(void)
{
	if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
		return;

	sysctl_sched_rt_runtime = old_rt_runtime;
	old_rt_runtime = -1;
}

static bool rcu_torture_boost_failed(unsigned long start, unsigned long end)
{
	if (end - start > test_boost_duration * HZ - HZ / 2) {
		VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
		n_rcu_torture_boost_failure++;

		return true; /* failed */
	}

	return false; /* passed */
}

static int rcu_torture_boost(void *arg)
{
	unsigned long call_rcu_time;
	unsigned long endtime;
	unsigned long oldstarttime;
	struct rcu_boost_inflight rbi = { .inflight = 0 };
	struct sched_param sp;

	VERBOSE_TOROUT_STRING("rcu_torture_boost started");

	/* Set real-time priority. */
	sp.sched_priority = 1;
	if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) {
		VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!");
		n_rcu_torture_boost_rterror++;
	}

	init_rcu_head_on_stack(&rbi.rcu);
	/* Each pass through the following loop does one boost-test cycle. */
	do {
		/* Track if the test failed already in this test interval? */
		bool failed = false;

		/* Increment n_rcu_torture_boosts once per boost-test */
		while (!kthread_should_stop()) {
			if (mutex_trylock(&boost_mutex)) {
				n_rcu_torture_boosts++;
				mutex_unlock(&boost_mutex);
				break;
			}
			schedule_timeout_uninterruptible(1);
		}
		if (kthread_should_stop())
			goto checkwait;

		/* Wait for the next test interval. */
		oldstarttime = boost_starttime;
		while (ULONG_CMP_LT(jiffies, oldstarttime)) {
			schedule_timeout_interruptible(oldstarttime - jiffies);
			stutter_wait("rcu_torture_boost");
			if (torture_must_stop())
				goto checkwait;
		}

		/* Do one boost-test interval. */
		endtime = oldstarttime + test_boost_duration * HZ;
		call_rcu_time = jiffies;
		while (ULONG_CMP_LT(jiffies, endtime)) {
			/* If we don't have a callback in flight, post one. */
			if (!smp_load_acquire(&rbi.inflight)) {
				/* RCU core before ->inflight = 1. */
				smp_store_release(&rbi.inflight, 1);
				call_rcu(&rbi.rcu, rcu_torture_boost_cb);
				/* Check if the boost test failed */
				failed = failed ||
					 rcu_torture_boost_failed(call_rcu_time,
								 jiffies);
				call_rcu_time = jiffies;
			}
			stutter_wait("rcu_torture_boost");
			if (torture_must_stop())
				goto checkwait;
		}

		/*
		 * If boost never happened, then inflight will always be 1, in
		 * this case the boost check would never happen in the above
		 * loop so do another one here.
		 */
		if (!failed && smp_load_acquire(&rbi.inflight))
			rcu_torture_boost_failed(call_rcu_time, jiffies);

		/*
		 * Set the start time of the next test interval.
		 * Yes, this is vulnerable to long delays, but such
		 * delays simply cause a false negative for the next
		 * interval.  Besides, we are running at RT priority,
		 * so delays should be relatively rare.
		 */
		while (oldstarttime == boost_starttime &&
		       !kthread_should_stop()) {
			if (mutex_trylock(&boost_mutex)) {
				boost_starttime = jiffies +
						  test_boost_interval * HZ;
				mutex_unlock(&boost_mutex);
				break;
			}
			schedule_timeout_uninterruptible(1);
		}

		/* Go do the stutter. */
checkwait:	stutter_wait("rcu_torture_boost");
	} while (!torture_must_stop());

	/* Clean up and exit. */
	while (!kthread_should_stop() || smp_load_acquire(&rbi.inflight)) {
		torture_shutdown_absorb("rcu_torture_boost");
		schedule_timeout_uninterruptible(1);
	}
	destroy_rcu_head_on_stack(&rbi.rcu);
	torture_kthread_stopping("rcu_torture_boost");
	return 0;
}

/*
 * RCU torture force-quiescent-state kthread.  Repeatedly induces
 * bursts of calls to force_quiescent_state(), increasing the probability
 * of occurrence of some important types of race conditions.
 */
static int
rcu_torture_fqs(void *arg)
{
	unsigned long fqs_resume_time;
	int fqs_burst_remaining;

	VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
	do {
		fqs_resume_time = jiffies + fqs_stutter * HZ;
		while (ULONG_CMP_LT(jiffies, fqs_resume_time) &&
		       !kthread_should_stop()) {
			schedule_timeout_interruptible(1);
		}
		fqs_burst_remaining = fqs_duration;
		while (fqs_burst_remaining > 0 &&
		       !kthread_should_stop()) {
			cur_ops->fqs();
			udelay(fqs_holdoff);
			fqs_burst_remaining -= fqs_holdoff;
		}
		stutter_wait("rcu_torture_fqs");
	} while (!torture_must_stop());
	torture_kthread_stopping("rcu_torture_fqs");
	return 0;
}

/*
 * RCU torture writer kthread.  Repeatedly substitutes a new structure
 * for that pointed to by rcu_torture_current, freeing the old structure
 * after a series of grace periods (the "pipeline").
 */
static int
rcu_torture_writer(void *arg)
{
	bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
	int expediting = 0;
	unsigned long gp_snap;
	bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
	bool gp_sync1 = gp_sync;
	int i;
	struct rcu_torture *rp;
	struct rcu_torture *old_rp;
	static DEFINE_TORTURE_RANDOM(rand);
	int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC,
			   RTWS_COND_GET, RTWS_SYNC };
	int nsynctypes = 0;

	VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
	if (!can_expedite)
		pr_alert("%s" TORTURE_FLAG
			 " GP expediting controlled from boot/sysfs for %s.\n",
			 torture_type, cur_ops->name);

	/* Initialize synctype[] array.  If none set, take default. */
	if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1)
		gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
	if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) {
		synctype[nsynctypes++] = RTWS_COND_GET;
		pr_info("%s: Testing conditional GPs.\n", __func__);
	} else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) {
		pr_alert("%s: gp_cond without primitives.\n", __func__);
	}
	if (gp_exp1 && cur_ops->exp_sync) {
		synctype[nsynctypes++] = RTWS_EXP_SYNC;
		pr_info("%s: Testing expedited GPs.\n", __func__);
	} else if (gp_exp && !cur_ops->exp_sync) {
		pr_alert("%s: gp_exp without primitives.\n", __func__);
	}
	if (gp_normal1 && cur_ops->deferred_free) {
		synctype[nsynctypes++] = RTWS_DEF_FREE;
		pr_info("%s: Testing asynchronous GPs.\n", __func__);
	} else if (gp_normal && !cur_ops->deferred_free) {
		pr_alert("%s: gp_normal without primitives.\n", __func__);
	}
	if (gp_sync1 && cur_ops->sync) {
		synctype[nsynctypes++] = RTWS_SYNC;
		pr_info("%s: Testing normal GPs.\n", __func__);
	} else if (gp_sync && !cur_ops->sync) {
		pr_alert("%s: gp_sync without primitives.\n", __func__);
	}
	if (WARN_ONCE(nsynctypes == 0,
		      "rcu_torture_writer: No update-side primitives.\n")) {
		/*
		 * No updates primitives, so don't try updating.
		 * The resulting test won't be testing much, hence the
		 * above WARN_ONCE().
		 */
		rcu_torture_writer_state = RTWS_STOPPING;
		torture_kthread_stopping("rcu_torture_writer");
	}

	do {
		rcu_torture_writer_state = RTWS_FIXED_DELAY;
		schedule_timeout_uninterruptible(1);
		rp = rcu_torture_alloc();
		if (rp == NULL)
			continue;
		rp->rtort_pipe_count = 0;
		rcu_torture_writer_state = RTWS_DELAY;
		udelay(torture_random(&rand) & 0x3ff);
		rcu_torture_writer_state = RTWS_REPLACE;
		old_rp = rcu_dereference_check(rcu_torture_current,
					       current == writer_task);
		rp->rtort_mbtest = 1;
		rcu_assign_pointer(rcu_torture_current, rp);
		smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
		if (old_rp) {
			i = old_rp->rtort_pipe_count;
			if (i > RCU_TORTURE_PIPE_LEN)
				i = RCU_TORTURE_PIPE_LEN;
			atomic_inc(&rcu_torture_wcount[i]);
			old_rp->rtort_pipe_count++;
			switch (synctype[torture_random(&rand) % nsynctypes]) {
			case RTWS_DEF_FREE:
				rcu_torture_writer_state = RTWS_DEF_FREE;
				cur_ops->deferred_free(old_rp);
				break;
			case RTWS_EXP_SYNC:
				rcu_torture_writer_state = RTWS_EXP_SYNC;
				cur_ops->exp_sync();
				rcu_torture_pipe_update(old_rp);
				break;
			case RTWS_COND_GET:
				rcu_torture_writer_state = RTWS_COND_GET;
				gp_snap = cur_ops->get_state();
				i = torture_random(&rand) % 16;
				if (i != 0)
					schedule_timeout_interruptible(i);
				udelay(torture_random(&rand) % 1000);
				rcu_torture_writer_state = RTWS_COND_SYNC;
				cur_ops->cond_sync(gp_snap);
				rcu_torture_pipe_update(old_rp);
				break;
			case RTWS_SYNC:
				rcu_torture_writer_state = RTWS_SYNC;
				cur_ops->sync();
				rcu_torture_pipe_update(old_rp);
				break;
			default:
				WARN_ON_ONCE(1);
				break;
			}
		}
		WRITE_ONCE(rcu_torture_current_version,
			   rcu_torture_current_version + 1);
		/* Cycle through nesting levels of rcu_expedite_gp() calls. */
		if (can_expedite &&
		    !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
			WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
			if (expediting >= 0)
				rcu_expedite_gp();
			else
				rcu_unexpedite_gp();
			if (++expediting > 3)
				expediting = -expediting;
		} else if (!can_expedite) { /* Disabled during boot, recheck. */
			can_expedite = !rcu_gp_is_expedited() &&
				       !rcu_gp_is_normal();
		}
		rcu_torture_writer_state = RTWS_STUTTER;
		if (stutter_wait("rcu_torture_writer"))
			for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
				if (list_empty(&rcu_tortures[i].rtort_free))
					WARN_ON_ONCE(1);
	} while (!torture_must_stop());
	/* Reset expediting back to unexpedited. */
	if (expediting > 0)
		expediting = -expediting;
	while (can_expedite && expediting++ < 0)
		rcu_unexpedite_gp();
	WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
	if (!can_expedite)
		pr_alert("%s" TORTURE_FLAG
			 " Dynamic grace-period expediting was disabled.\n",
			 torture_type);
	rcu_torture_writer_state = RTWS_STOPPING;
	torture_kthread_stopping("rcu_torture_writer");
	return 0;
}

/*
 * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 * delay between calls.
 */
static int
rcu_torture_fakewriter(void *arg)
{
	DEFINE_TORTURE_RANDOM(rand);

	VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
	set_user_nice(current, MAX_NICE);

	do {
		schedule_timeout_uninterruptible(1 + torture_random(&rand)%10);
		udelay(torture_random(&rand) & 0x3ff);
		if (cur_ops->cb_barrier != NULL &&
		    torture_random(&rand) % (nfakewriters * 8) == 0) {
			cur_ops->cb_barrier();
		} else if (gp_normal == gp_exp) {
			if (cur_ops->sync && torture_random(&rand) & 0x80)
				cur_ops->sync();
			else if (cur_ops->exp_sync)
				cur_ops->exp_sync();
		} else if (gp_normal && cur_ops->sync) {
			cur_ops->sync();
		} else if (cur_ops->exp_sync) {
			cur_ops->exp_sync();
		}
		stutter_wait("rcu_torture_fakewriter");
	} while (!torture_must_stop());

	torture_kthread_stopping("rcu_torture_fakewriter");
	return 0;
}

static void rcu_torture_timer_cb(struct rcu_head *rhp)
{
	kfree(rhp);
}

/*
 * Do one extension of an RCU read-side critical section using the
 * current reader state in readstate (set to zero for initial entry
 * to extended critical section), set the new state as specified by
 * newstate (set to zero for final exit from extended critical section),
 * and random-number-generator state in trsp.  If this is neither the
 * beginning or end of the critical section and if there was actually a
 * change, do a ->read_delay().
 */
static void rcutorture_one_extend(int *readstate, int newstate,
				  struct torture_random_state *trsp,
				  struct rt_read_seg *rtrsp)
{
	int idxnew = -1;
	int idxold = *readstate;
	int statesnew = ~*readstate & newstate;
	int statesold = *readstate & ~newstate;

	WARN_ON_ONCE(idxold < 0);
	WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);
	rtrsp->rt_readstate = newstate;

	/* First, put new protection in place to avoid critical-section gap. */
	if (statesnew & RCUTORTURE_RDR_BH)
		local_bh_disable();
	if (statesnew & RCUTORTURE_RDR_IRQ)
		local_irq_disable();
	if (statesnew & RCUTORTURE_RDR_PREEMPT)
		preempt_disable();
	if (statesnew & RCUTORTURE_RDR_RBH)
		rcu_read_lock_bh();
	if (statesnew & RCUTORTURE_RDR_SCHED)
		rcu_read_lock_sched();
	if (statesnew & RCUTORTURE_RDR_RCU)
		idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;

	/* Next, remove old protection, irq first due to bh conflict. */
	if (statesold & RCUTORTURE_RDR_IRQ)
		local_irq_enable();
	if (statesold & RCUTORTURE_RDR_BH)
		local_bh_enable();
	if (statesold & RCUTORTURE_RDR_PREEMPT)
		preempt_enable();
	if (statesold & RCUTORTURE_RDR_RBH)
		rcu_read_unlock_bh();
	if (statesold & RCUTORTURE_RDR_SCHED)
		rcu_read_unlock_sched();
	if (statesold & RCUTORTURE_RDR_RCU)
		cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);

	/* Delay if neither beginning nor end and there was a change. */
	if ((statesnew || statesold) && *readstate && newstate)
		cur_ops->read_delay(trsp, rtrsp);

	/* Update the reader state. */
	if (idxnew == -1)
		idxnew = idxold & ~RCUTORTURE_RDR_MASK;
	WARN_ON_ONCE(idxnew < 0);
	WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1);
	*readstate = idxnew | newstate;
	WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0);
	WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1);
}

/* Return the biggest extendables mask given current RCU and boot parameters. */
static int rcutorture_extend_mask_max(void)
{
	int mask;

	WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
	mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
	mask = mask | RCUTORTURE_RDR_RCU;
	return mask;
}

/* Return a random protection state mask, but with at least one bit set. */
static int
rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
{
	int mask = rcutorture_extend_mask_max();
	unsigned long randmask1 = torture_random(trsp) >> 8;
	unsigned long randmask2 = randmask1 >> 3;

	WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
	/* Mostly only one bit (need preemption!), sometimes lots of bits. */
	if (!(randmask1 & 0x7))
		mask = mask & randmask2;
	else
		mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
	/* Can't enable bh w/irq disabled. */
	if ((mask & RCUTORTURE_RDR_IRQ) &&
	    ((!(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) ||
	     (!(mask & RCUTORTURE_RDR_RBH) && (oldmask & RCUTORTURE_RDR_RBH))))
		mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
	return mask ?: RCUTORTURE_RDR_RCU;
}

/*
 * Do a randomly selected number of extensions of an existing RCU read-side
 * critical section.
 */
static struct rt_read_seg *
rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
		       struct rt_read_seg *rtrsp)
{
	int i;
	int j;
	int mask = rcutorture_extend_mask_max();

	WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
	if (!((mask - 1) & mask))
		return rtrsp;  /* Current RCU reader not extendable. */
	/* Bias towards larger numbers of loops. */
	i = (torture_random(trsp) >> 3);
	i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
	for (j = 0; j < i; j++) {
		mask = rcutorture_extend_mask(*readstate, trsp);
		rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
	}
	return &rtrsp[j];
}

/*
 * Do one read-side critical section, returning false if there was
 * no data to read.  Can be invoked both from process context and
 * from a timer handler.
 */
static bool rcu_torture_one_read(struct torture_random_state *trsp)
{
	int i;
	unsigned long started;
	unsigned long completed;
	int newstate;
	struct rcu_torture *p;
	int pipe_count;
	int readstate = 0;
	struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
	struct rt_read_seg *rtrsp = &rtseg[0];
	struct rt_read_seg *rtrsp1;
	unsigned long long ts;

	newstate = rcutorture_extend_mask(readstate, trsp);
	rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
	started = cur_ops->get_gp_seq();
	ts = rcu_trace_clock_local();
	p = rcu_dereference_check(rcu_torture_current,
				  rcu_read_lock_bh_held() ||
				  rcu_read_lock_sched_held() ||
				  srcu_read_lock_held(srcu_ctlp) ||
				  torturing_tasks());
	if (p == NULL) {
		/* Wait for rcu_torture_writer to get underway */
		rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
		return false;
	}
	if (p->rtort_mbtest == 0)
		atomic_inc(&n_rcu_torture_mberror);
	rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
	preempt_disable();
	pipe_count = p->rtort_pipe_count;
	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
		/* Should not happen, but... */
		pipe_count = RCU_TORTURE_PIPE_LEN;
	}
	completed = cur_ops->get_gp_seq();
	if (pipe_count > 1) {
		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
					  ts, started, completed);
		rcu_ftrace_dump(DUMP_ALL);
	}
	__this_cpu_inc(rcu_torture_count[pipe_count]);
	completed = rcutorture_seq_diff(completed, started);
	if (completed > RCU_TORTURE_PIPE_LEN) {
		/* Should not happen, but... */
		completed = RCU_TORTURE_PIPE_LEN;
	}
	__this_cpu_inc(rcu_torture_batch[completed]);
	preempt_enable();
	rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
	WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);

	/* If error or close call, record the sequence of reader protections. */
	if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
		i = 0;
		for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
			err_segs[i++] = *rtrsp1;
		rt_read_nsegs = i;
	}

	return true;
}

static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);

/*
 * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
 * incrementing the corresponding element of the pipeline array.  The
 * counter in the element should never be greater than 1, otherwise, the
 * RCU implementation is broken.
 */
static void rcu_torture_timer(struct timer_list *unused)
{
	atomic_long_inc(&n_rcu_torture_timers);
	(void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand));

	/* Test call_rcu() invocation from interrupt handler. */
	if (cur_ops->call) {
		struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT);

		if (rhp)
			cur_ops->call(rhp, rcu_torture_timer_cb);
	}
}

/*
 * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 * incrementing the corresponding element of the pipeline array.  The
 * counter in the element should never be greater than 1, otherwise, the
 * RCU implementation is broken.
 */
static int
rcu_torture_reader(void *arg)
{
	unsigned long lastsleep = jiffies;
	long myid = (long)arg;
	int mynumonline = myid;
	DEFINE_TORTURE_RANDOM(rand);
	struct timer_list t;

	VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
	set_user_nice(current, MAX_NICE);
	if (irqreader && cur_ops->irq_capable)
		timer_setup_on_stack(&t, rcu_torture_timer, 0);

	do {
		if (irqreader && cur_ops->irq_capable) {
			if (!timer_pending(&t))
				mod_timer(&t, jiffies + 1);
		}
		if (!rcu_torture_one_read(&rand))
			schedule_timeout_interruptible(HZ);
		if (time_after(jiffies, lastsleep)) {
			schedule_timeout_interruptible(1);
			lastsleep = jiffies + 10;
		}
		while (num_online_cpus() < mynumonline && !torture_must_stop())
			schedule_timeout_interruptible(HZ / 5);
		stutter_wait("rcu_torture_reader");
	} while (!torture_must_stop());
	if (irqreader && cur_ops->irq_capable) {
		del_timer_sync(&t);
		destroy_timer_on_stack(&t);
	}
	torture_kthread_stopping("rcu_torture_reader");
	return 0;
}

/*
 * Print torture statistics.  Caller must ensure that there is only
 * one call to this function at a given time!!!  This is normally
 * accomplished by relying on the module system to only have one copy
 * of the module loaded, and then by giving the rcu_torture_stats
 * kthread full control (or the init/cleanup functions when rcu_torture_stats
 * thread is not running).
 */
static void
rcu_torture_stats_print(void)
{
	int cpu;
	int i;
	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
	static unsigned long rtcv_snap = ULONG_MAX;
	static bool splatted;
	struct task_struct *wtp;

	for_each_possible_cpu(cpu) {
		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
			pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
			batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
		}
	}
	for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
		if (pipesummary[i] != 0)
			break;
	}

	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
	pr_cont("rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
		rcu_torture_current,
		rcu_torture_current_version,
		list_empty(&rcu_torture_freelist),
		atomic_read(&n_rcu_torture_alloc),
		atomic_read(&n_rcu_torture_alloc_fail),
		atomic_read(&n_rcu_torture_free));
	pr_cont("rtmbe: %d rtbe: %ld rtbke: %ld rtbre: %ld ",
		atomic_read(&n_rcu_torture_mberror),
		n_rcu_torture_barrier_error,
		n_rcu_torture_boost_ktrerror,
		n_rcu_torture_boost_rterror);
	pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
		n_rcu_torture_boost_failure,
		n_rcu_torture_boosts,
		atomic_long_read(&n_rcu_torture_timers));
	torture_onoff_stats();
	pr_cont("barrier: %ld/%ld:%ld\n",
		n_barrier_successes,
		n_barrier_attempts,
		n_rcu_torture_barrier_error);

	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
	if (atomic_read(&n_rcu_torture_mberror) != 0 ||
	    n_rcu_torture_barrier_error != 0 ||
	    n_rcu_torture_boost_ktrerror != 0 ||
	    n_rcu_torture_boost_rterror != 0 ||
	    n_rcu_torture_boost_failure != 0 ||
	    i > 1) {
		pr_cont("%s", "!!! ");
		atomic_inc(&n_rcu_torture_error);
		WARN_ON_ONCE(1);
	}
	pr_cont("Reader Pipe: ");
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
		pr_cont(" %ld", pipesummary[i]);
	pr_cont("\n");

	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
	pr_cont("Reader Batch: ");
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
		pr_cont(" %ld", batchsummary[i]);
	pr_cont("\n");

	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
	pr_cont("Free-Block Circulation: ");
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
		pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
	}
	pr_cont("\n");

	if (cur_ops->stats)
		cur_ops->stats();
	if (rtcv_snap == rcu_torture_current_version &&
	    rcu_torture_current != NULL) {
		int __maybe_unused flags = 0;
		unsigned long __maybe_unused gp_seq = 0;

		rcutorture_get_gp_data(cur_ops->ttype,
				       &flags, &gp_seq);
		srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
					&flags, &gp_seq);
		wtp = READ_ONCE(writer_task);
		pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#lx cpu %d\n",
			 rcu_torture_writer_state_getname(),
			 rcu_torture_writer_state, gp_seq, flags,
			 wtp == NULL ? ~0UL : wtp->state,
			 wtp == NULL ? -1 : (int)task_cpu(wtp));
		if (!splatted && wtp) {
			sched_show_task(wtp);
			splatted = true;
		}
		show_rcu_gp_kthreads();
		rcu_ftrace_dump(DUMP_ALL);
	}
	rtcv_snap = rcu_torture_current_version;
}

/*
 * Periodically prints torture statistics, if periodic statistics printing
 * was specified via the stat_interval module parameter.
 */
static int
rcu_torture_stats(void *arg)
{
	VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
	do {
		schedule_timeout_interruptible(stat_interval * HZ);
		rcu_torture_stats_print();
		torture_shutdown_absorb("rcu_torture_stats");
	} while (!torture_must_stop());
	torture_kthread_stopping("rcu_torture_stats");
	return 0;
}

static void
rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
{
	pr_alert("%s" TORTURE_FLAG
		 "--- %s: nreaders=%d nfakewriters=%d "
		 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
		 "shuffle_interval=%d stutter=%d irqreader=%d "
		 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
		 "test_boost=%d/%d test_boost_interval=%d "
		 "test_boost_duration=%d shutdown_secs=%d "
		 "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
		 "n_barrier_cbs=%d "
		 "onoff_interval=%d onoff_holdoff=%d\n",
		 torture_type, tag, nrealreaders, nfakewriters,
		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
		 test_boost, cur_ops->can_boost,
		 test_boost_interval, test_boost_duration, shutdown_secs,
		 stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
		 n_barrier_cbs,
		 onoff_interval, onoff_holdoff);
}

static int rcutorture_booster_cleanup(unsigned int cpu)
{
	struct task_struct *t;

	if (boost_tasks[cpu] == NULL)
		return 0;
	mutex_lock(&boost_mutex);
	t = boost_tasks[cpu];
	boost_tasks[cpu] = NULL;
	rcu_torture_enable_rt_throttle();
	mutex_unlock(&boost_mutex);

	/* This must be outside of the mutex, otherwise deadlock! */
	torture_stop_kthread(rcu_torture_boost, t);
	return 0;
}

static int rcutorture_booster_init(unsigned int cpu)
{
	int retval;

	if (boost_tasks[cpu] != NULL)
		return 0;  /* Already created, nothing more to do. */

	/* Don't allow time recalculation while creating a new task. */
	mutex_lock(&boost_mutex);
	rcu_torture_disable_rt_throttle();
	VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
	boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
						  cpu_to_node(cpu),
						  "rcu_torture_boost");
	if (IS_ERR(boost_tasks[cpu])) {
		retval = PTR_ERR(boost_tasks[cpu]);
		VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
		n_rcu_torture_boost_ktrerror++;
		boost_tasks[cpu] = NULL;
		mutex_unlock(&boost_mutex);
		return retval;
	}
	kthread_bind(boost_tasks[cpu], cpu);
	wake_up_process(boost_tasks[cpu]);
	mutex_unlock(&boost_mutex);
	return 0;
}

/*
 * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
 * induces a CPU stall for the time specified by stall_cpu.
 */
static int rcu_torture_stall(void *args)
{
	unsigned long stop_at;

	VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
	if (stall_cpu_holdoff > 0) {
		VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
		schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
		VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
	}
	if (!kthread_should_stop()) {
		stop_at = ktime_get_seconds() + stall_cpu;
		/* RCU CPU stall is expected behavior in following code. */
		rcu_read_lock();
		if (stall_cpu_irqsoff)
			local_irq_disable();
		else
			preempt_disable();
		pr_alert("rcu_torture_stall start on CPU %d.\n",
			 smp_processor_id());
		while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
				    stop_at))
			continue;  /* Induce RCU CPU stall warning. */
		if (stall_cpu_irqsoff)
			local_irq_enable();
		else
			preempt_enable();
		rcu_read_unlock();
		pr_alert("rcu_torture_stall end.\n");
	}
	torture_shutdown_absorb("rcu_torture_stall");
	while (!kthread_should_stop())
		schedule_timeout_interruptible(10 * HZ);
	return 0;
}

/* Spawn CPU-stall kthread, if stall_cpu specified. */
static int __init rcu_torture_stall_init(void)
{
	if (stall_cpu <= 0)
		return 0;
	return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
}

/* State structure for forward-progress self-propagating RCU callback. */
struct fwd_cb_state {
	struct rcu_head rh;
	int stop;
};

/*
 * Forward-progress self-propagating RCU callback function.  Because
 * callbacks run from softirq, this function is an implicit RCU read-side
 * critical section.
 */
static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
{
	struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);

	if (READ_ONCE(fcsp->stop)) {
		WRITE_ONCE(fcsp->stop, 2);
		return;
	}
	cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
}

/* State for continuous-flood RCU callbacks. */
struct rcu_fwd_cb {
	struct rcu_head rh;
	struct rcu_fwd_cb *rfc_next;
	int rfc_gps;
};
static DEFINE_SPINLOCK(rcu_fwd_lock);
static struct rcu_fwd_cb *rcu_fwd_cb_head;
static struct rcu_fwd_cb **rcu_fwd_cb_tail = &rcu_fwd_cb_head;
static long n_launders_cb;
static unsigned long rcu_fwd_startat;
static bool rcu_fwd_emergency_stop;
#define MAX_FWD_CB_JIFFIES	(8 * HZ) /* Maximum CB test duration. */
#define MIN_FWD_CB_LAUNDERS	3	/* This many CB invocations to count. */
#define MIN_FWD_CBS_LAUNDERED	100	/* Number of counted CBs. */
#define FWD_CBS_HIST_DIV	10	/* Histogram buckets/second. */
struct rcu_launder_hist {
	long n_launders;
	unsigned long launder_gp_seq;
};
#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
static struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
static unsigned long rcu_launder_gp_seq_start;

static void rcu_torture_fwd_cb_hist(void)
{
	unsigned long gps;
	unsigned long gps_old;
	int i;
	int j;

	for (i = ARRAY_SIZE(n_launders_hist) - 1; i > 0; i--)
		if (n_launders_hist[i].n_launders > 0)
			break;
	pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",
		 __func__, jiffies - rcu_fwd_startat);
	gps_old = rcu_launder_gp_seq_start;
	for (j = 0; j <= i; j++) {
		gps = n_launders_hist[j].launder_gp_seq;
		pr_cont(" %ds/%d: %ld:%ld",
			j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j].n_launders,
			rcutorture_seq_diff(gps, gps_old));
		gps_old = gps;
	}
	pr_cont("\n");
}

/* Callback function for continuous-flood RCU callbacks. */
static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
{
	unsigned long flags;
	int i;
	struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);
	struct rcu_fwd_cb **rfcpp;

	rfcp->rfc_next = NULL;
	rfcp->rfc_gps++;
	spin_lock_irqsave(&rcu_fwd_lock, flags);
	rfcpp = rcu_fwd_cb_tail;
	rcu_fwd_cb_tail = &rfcp->rfc_next;
	WRITE_ONCE(*rfcpp, rfcp);
	WRITE_ONCE(n_launders_cb, n_launders_cb + 1);
	i = ((jiffies - rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
	if (i >= ARRAY_SIZE(n_launders_hist))
		i = ARRAY_SIZE(n_launders_hist) - 1;
	n_launders_hist[i].n_launders++;
	n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
	spin_unlock_irqrestore(&rcu_fwd_lock, flags);
}

/*
 * Free all callbacks on the rcu_fwd_cb_head list, either because the
 * test is over or because we hit an OOM event.
 */
static unsigned long rcu_torture_fwd_prog_cbfree(void)
{
	unsigned long flags;
	unsigned long freed = 0;
	struct rcu_fwd_cb *rfcp;

	for (;;) {
		spin_lock_irqsave(&rcu_fwd_lock, flags);
		rfcp = rcu_fwd_cb_head;
		if (!rfcp)
			break;
		rcu_fwd_cb_head = rfcp->rfc_next;
		if (!rcu_fwd_cb_head)
			rcu_fwd_cb_tail = &rcu_fwd_cb_head;
		spin_unlock_irqrestore(&rcu_fwd_lock, flags);
		kfree(rfcp);
		freed++;
	}
	spin_unlock_irqrestore(&rcu_fwd_lock, flags);
	return freed;
}

/* Carry out need_resched()/cond_resched() forward-progress testing. */
static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
{
	unsigned long cver;
	unsigned long dur;
	struct fwd_cb_state fcs;
	unsigned long gps;
	int idx;
	int sd;
	int sd4;
	bool selfpropcb = false;
	unsigned long stopat;
	static DEFINE_TORTURE_RANDOM(trs);

	if  (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
		init_rcu_head_on_stack(&fcs.rh);
		selfpropcb = true;
	}

	/* Tight loop containing cond_resched(). */
	if  (selfpropcb) {
		WRITE_ONCE(fcs.stop, 0);
		cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
	}
	cver = READ_ONCE(rcu_torture_current_version);
	gps = cur_ops->get_gp_seq();
	sd = cur_ops->stall_dur() + 1;
	sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
	dur = sd4 + torture_random(&trs) % (sd - sd4);
	WRITE_ONCE(rcu_fwd_startat, jiffies);
	stopat = rcu_fwd_startat + dur;
	while (time_before(jiffies, stopat) &&
	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
		idx = cur_ops->readlock();
		udelay(10);
		cur_ops->readunlock(idx);
		if (!fwd_progress_need_resched || need_resched())
			cond_resched();
	}
	(*tested_tries)++;
	if (!time_before(jiffies, stopat) &&
	    !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
		(*tested)++;
		cver = READ_ONCE(rcu_torture_current_version) - cver;
		gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
		WARN_ON(!cver && gps < 2);
		pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps);
	}
	if (selfpropcb) {
		WRITE_ONCE(fcs.stop, 1);
		cur_ops->sync(); /* Wait for running CB to complete. */
		cur_ops->cb_barrier(); /* Wait for queued callbacks. */
	}

	if (selfpropcb) {
		WARN_ON(READ_ONCE(fcs.stop) != 2);
		destroy_rcu_head_on_stack(&fcs.rh);
	}
}

/* Carry out call_rcu() forward-progress testing. */
static void rcu_torture_fwd_prog_cr(void)
{
	unsigned long cver;
	unsigned long gps;
	int i;
	long n_launders;
	long n_launders_cb_snap;
	long n_launders_sa;
	long n_max_cbs;
	long n_max_gps;
	struct rcu_fwd_cb *rfcp;
	struct rcu_fwd_cb *rfcpn;
	unsigned long stopat;
	unsigned long stoppedat;

	if (READ_ONCE(rcu_fwd_emergency_stop))
		return; /* Get out of the way quickly, no GP wait! */

	/* Loop continuously posting RCU callbacks. */
	WRITE_ONCE(rcu_fwd_cb_nodelay, true);
	cur_ops->sync(); /* Later readers see above write. */
	WRITE_ONCE(rcu_fwd_startat, jiffies);
	stopat = rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
	n_launders = 0;
	n_launders_cb = 0;
	n_launders_sa = 0;
	n_max_cbs = 0;
	n_max_gps = 0;
	for (i = 0; i < ARRAY_SIZE(n_launders_hist); i++)
		n_launders_hist[i].n_launders = 0;
	cver = READ_ONCE(rcu_torture_current_version);
	gps = cur_ops->get_gp_seq();
	rcu_launder_gp_seq_start = gps;
	while (time_before(jiffies, stopat) &&
	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
		rfcp = READ_ONCE(rcu_fwd_cb_head);
		rfcpn = NULL;
		if (rfcp)
			rfcpn = READ_ONCE(rfcp->rfc_next);
		if (rfcpn) {
			if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
			    ++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
				break;
			rcu_fwd_cb_head = rfcpn;
			n_launders++;
			n_launders_sa++;
		} else {
			rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
			if (WARN_ON_ONCE(!rfcp)) {
				schedule_timeout_interruptible(1);
				continue;
			}
			n_max_cbs++;
			n_launders_sa = 0;
			rfcp->rfc_gps = 0;
		}
		cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
		cond_resched();
	}
	stoppedat = jiffies;
	n_launders_cb_snap = READ_ONCE(n_launders_cb);
	cver = READ_ONCE(rcu_torture_current_version) - cver;
	gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
	cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
	(void)rcu_torture_fwd_prog_cbfree();

	WRITE_ONCE(rcu_fwd_cb_nodelay, false);
	if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) {
		WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
		pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
			 __func__,
			 stoppedat - rcu_fwd_startat, jiffies - stoppedat,
			 n_launders + n_max_cbs - n_launders_cb_snap,
			 n_launders, n_launders_sa,
			 n_max_gps, n_max_cbs, cver, gps);
		rcu_torture_fwd_cb_hist();
	}
}


/*
 * OOM notifier, but this only prints diagnostic information for the
 * current forward-progress test.
 */
static int rcutorture_oom_notify(struct notifier_block *self,
				 unsigned long notused, void *nfreed)
{
	WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
	     __func__);
	rcu_torture_fwd_cb_hist();
	rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat)) / 2);
	WRITE_ONCE(rcu_fwd_emergency_stop, true);
	smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
	pr_info("%s: Freed %lu RCU callbacks.\n",
		__func__, rcu_torture_fwd_prog_cbfree());
	rcu_barrier();
	pr_info("%s: Freed %lu RCU callbacks.\n",
		__func__, rcu_torture_fwd_prog_cbfree());
	rcu_barrier();
	pr_info("%s: Freed %lu RCU callbacks.\n",
		__func__, rcu_torture_fwd_prog_cbfree());
	smp_mb(); /* Frees before return to avoid redoing OOM. */
	(*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
	pr_info("%s returning after OOM processing.\n", __func__);
	return NOTIFY_OK;
}

static struct notifier_block rcutorture_oom_nb = {
	.notifier_call = rcutorture_oom_notify
};

/* Carry out grace-period forward-progress testing. */
static int rcu_torture_fwd_prog(void *args)
{
	int tested = 0;
	int tested_tries = 0;

	VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
	rcu_bind_current_to_nocb();
	if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
		set_user_nice(current, MAX_NICE);
	do {
		schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
		WRITE_ONCE(rcu_fwd_emergency_stop, false);
		register_oom_notifier(&rcutorture_oom_nb);
		rcu_torture_fwd_prog_nr(&tested, &tested_tries);
		rcu_torture_fwd_prog_cr();
		unregister_oom_notifier(&rcutorture_oom_nb);

		/* Avoid slow periods, better to test when busy. */
		stutter_wait("rcu_torture_fwd_prog");
	} while (!torture_must_stop());
	/* Short runs might not contain a valid forward-progress attempt. */
	WARN_ON(!tested && tested_tries >= 5);
	pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
	torture_kthread_stopping("rcu_torture_fwd_prog");
	return 0;
}

/* If forward-progress checking is requested and feasible, spawn the thread. */
static int __init rcu_torture_fwd_prog_init(void)
{
	if (!fwd_progress)
		return 0; /* Not requested, so don't do it. */
	if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 ||
	    cur_ops == &rcu_busted_ops) {
		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
		return 0;
	}
	if (stall_cpu > 0) {
		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
		if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
			return -EINVAL; /* In module, can fail back to user. */
		WARN_ON(1); /* Make sure rcutorture notices conflict. */
		return 0;
	}
	if (fwd_progress_holdoff <= 0)
		fwd_progress_holdoff = 1;
	if (fwd_progress_div <= 0)
		fwd_progress_div = 4;
	return torture_create_kthread(rcu_torture_fwd_prog,
				      NULL, fwd_prog_task);
}

/* Callback function for RCU barrier testing. */
static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
{
	atomic_inc(&barrier_cbs_invoked);
}

/* kthread function to register callbacks used to test RCU barriers. */
static int rcu_torture_barrier_cbs(void *arg)
{
	long myid = (long)arg;
	bool lastphase = 0;
	bool newphase;
	struct rcu_head rcu;

	init_rcu_head_on_stack(&rcu);
	VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
	set_user_nice(current, MAX_NICE);
	do {
		wait_event(barrier_cbs_wq[myid],
			   (newphase =
			    smp_load_acquire(&barrier_phase)) != lastphase ||
			   torture_must_stop());
		lastphase = newphase;
		if (torture_must_stop())
			break;
		/*
		 * The above smp_load_acquire() ensures barrier_phase load
		 * is ordered before the following ->call().
		 */
		local_irq_disable(); /* Just to test no-irq call_rcu(). */
		cur_ops->call(&rcu, rcu_torture_barrier_cbf);
		local_irq_enable();
		if (atomic_dec_and_test(&barrier_cbs_count))
			wake_up(&barrier_wq);
	} while (!torture_must_stop());
	if (cur_ops->cb_barrier != NULL)
		cur_ops->cb_barrier();
	destroy_rcu_head_on_stack(&rcu);
	torture_kthread_stopping("rcu_torture_barrier_cbs");
	return 0;
}

/* kthread function to drive and coordinate RCU barrier testing. */
static int rcu_torture_barrier(void *arg)
{
	int i;

	VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
	do {
		atomic_set(&barrier_cbs_invoked, 0);
		atomic_set(&barrier_cbs_count, n_barrier_cbs);
		/* Ensure barrier_phase ordered after prior assignments. */
		smp_store_release(&barrier_phase, !barrier_phase);
		for (i = 0; i < n_barrier_cbs; i++)
			wake_up(&barrier_cbs_wq[i]);
		wait_event(barrier_wq,
			   atomic_read(&barrier_cbs_count) == 0 ||
			   torture_must_stop());
		if (torture_must_stop())
			break;
		n_barrier_attempts++;
		cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
		if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
			n_rcu_torture_barrier_error++;
			pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
			       atomic_read(&barrier_cbs_invoked),
			       n_barrier_cbs);
			WARN_ON_ONCE(1);
		} else {
			n_barrier_successes++;
		}
		schedule_timeout_interruptible(HZ / 10);
	} while (!torture_must_stop());
	torture_kthread_stopping("rcu_torture_barrier");
	return 0;
}

/* Initialize RCU barrier testing. */
static int rcu_torture_barrier_init(void)
{
	int i;
	int ret;

	if (n_barrier_cbs <= 0)
		return 0;
	if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
		pr_alert("%s" TORTURE_FLAG
			 " Call or barrier ops missing for %s,\n",
			 torture_type, cur_ops->name);
		pr_alert("%s" TORTURE_FLAG
			 " RCU barrier testing omitted from run.\n",
			 torture_type);
		return 0;
	}
	atomic_set(&barrier_cbs_count, 0);
	atomic_set(&barrier_cbs_invoked, 0);
	barrier_cbs_tasks =
		kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]),
			GFP_KERNEL);
	barrier_cbs_wq =
		kcalloc(n_barrier_cbs, sizeof(barrier_cbs_wq[0]), GFP_KERNEL);
	if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
		return -ENOMEM;
	for (i = 0; i < n_barrier_cbs; i++) {
		init_waitqueue_head(&barrier_cbs_wq[i]);
		ret = torture_create_kthread(rcu_torture_barrier_cbs,
					     (void *)(long)i,
					     barrier_cbs_tasks[i]);
		if (ret)
			return ret;
	}
	return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
}

/* Clean up after RCU barrier testing. */
static void rcu_torture_barrier_cleanup(void)
{
	int i;

	torture_stop_kthread(rcu_torture_barrier, barrier_task);
	if (barrier_cbs_tasks != NULL) {
		for (i = 0; i < n_barrier_cbs; i++)
			torture_stop_kthread(rcu_torture_barrier_cbs,
					     barrier_cbs_tasks[i]);
		kfree(barrier_cbs_tasks);
		barrier_cbs_tasks = NULL;
	}
	if (barrier_cbs_wq != NULL) {
		kfree(barrier_cbs_wq);
		barrier_cbs_wq = NULL;
	}
}

static bool rcu_torture_can_boost(void)
{
	static int boost_warn_once;
	int prio;

	if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
		return false;

	prio = rcu_get_gp_kthreads_prio();
	if (!prio)
		return false;

	if (prio < 2) {
		if (boost_warn_once  == 1)
			return false;

		pr_alert("%s: WARN: RCU kthread priority too low to test boosting.  Skipping RCU boost test. Try passing rcutree.kthread_prio > 1 on the kernel command line.\n", KBUILD_MODNAME);
		boost_warn_once = 1;
		return false;
	}

	return true;
}

static enum cpuhp_state rcutor_hp;

static void
rcu_torture_cleanup(void)
{
	int firsttime;
	int flags = 0;
	unsigned long gp_seq = 0;
	int i;

	if (torture_cleanup_begin()) {
		if (cur_ops->cb_barrier != NULL)
			cur_ops->cb_barrier();
		return;
	}
	if (!cur_ops) {
		torture_cleanup_end();
		return;
	}

	rcu_torture_barrier_cleanup();
	torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
	torture_stop_kthread(rcu_torture_stall, stall_task);
	torture_stop_kthread(rcu_torture_writer, writer_task);

	if (reader_tasks) {
		for (i = 0; i < nrealreaders; i++)
			torture_stop_kthread(rcu_torture_reader,
					     reader_tasks[i]);
		kfree(reader_tasks);
	}
	rcu_torture_current = NULL;

	if (fakewriter_tasks) {
		for (i = 0; i < nfakewriters; i++) {
			torture_stop_kthread(rcu_torture_fakewriter,
					     fakewriter_tasks[i]);
		}
		kfree(fakewriter_tasks);
		fakewriter_tasks = NULL;
	}

	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
	pr_alert("%s:  End-test grace-period state: g%lu f%#x\n",
		 cur_ops->name, gp_seq, flags);
	torture_stop_kthread(rcu_torture_stats, stats_task);
	torture_stop_kthread(rcu_torture_fqs, fqs_task);
	if (rcu_torture_can_boost())
		cpuhp_remove_state(rcutor_hp);

	/*
	 * Wait for all RCU callbacks to fire, then do torture-type-specific
	 * cleanup operations.
	 */
	if (cur_ops->cb_barrier != NULL)
		cur_ops->cb_barrier();
	if (cur_ops->cleanup != NULL)
		cur_ops->cleanup();

	rcu_torture_stats_print();  /* -After- the stats thread is stopped! */

	if (err_segs_recorded) {
		pr_alert("Failure/close-call rcutorture reader segments:\n");
		if (rt_read_nsegs == 0)
			pr_alert("\t: No segments recorded!!!\n");
		firsttime = 1;
		for (i = 0; i < rt_read_nsegs; i++) {
			pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
			if (err_segs[i].rt_delay_jiffies != 0) {
				pr_cont("%s%ldjiffies", firsttime ? "" : "+",
					err_segs[i].rt_delay_jiffies);
				firsttime = 0;
			}
			if (err_segs[i].rt_delay_ms != 0) {
				pr_cont("%s%ldms", firsttime ? "" : "+",
					err_segs[i].rt_delay_ms);
				firsttime = 0;
			}
			if (err_segs[i].rt_delay_us != 0) {
				pr_cont("%s%ldus", firsttime ? "" : "+",
					err_segs[i].rt_delay_us);
				firsttime = 0;
			}
			pr_cont("%s\n",
				err_segs[i].rt_preempted ? "preempted" : "");

		}
	}
	if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
		rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
	else if (torture_onoff_failures())
		rcu_torture_print_module_parms(cur_ops,
					       "End of test: RCU_HOTPLUG");
	else
		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
	torture_cleanup_end();
}

#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
static void rcu_torture_leak_cb(struct rcu_head *rhp)
{
}

static void rcu_torture_err_cb(struct rcu_head *rhp)
{
	/*
	 * This -might- happen due to race conditions, but is unlikely.
	 * The scenario that leads to this happening is that the
	 * first of the pair of duplicate callbacks is queued,
	 * someone else starts a grace period that includes that
	 * callback, then the second of the pair must wait for the
	 * next grace period.  Unlikely, but can happen.  If it
	 * does happen, the debug-objects subsystem won't have splatted.
	 */
	pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
}
#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */

/*
 * Verify that double-free causes debug-objects to complain, but only
 * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
 * cannot be carried out.
 */
static void rcu_test_debug_objects(void)
{
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
	struct rcu_head rh1;
	struct rcu_head rh2;

	init_rcu_head_on_stack(&rh1);
	init_rcu_head_on_stack(&rh2);
	pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);

	/* Try to queue the rh2 pair of callbacks for the same grace period. */
	preempt_disable(); /* Prevent preemption from interrupting test. */
	rcu_read_lock(); /* Make it impossible to finish a grace period. */
	call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
	local_irq_disable(); /* Make it harder to start a new grace period. */
	call_rcu(&rh2, rcu_torture_leak_cb);
	call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
	local_irq_enable();
	rcu_read_unlock();
	preempt_enable();

	/* Wait for them all to get done so we can safely return. */
	rcu_barrier();
	pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
	destroy_rcu_head_on_stack(&rh1);
	destroy_rcu_head_on_stack(&rh2);
#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
	pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
}

static void rcutorture_sync(void)
{
	static unsigned long n;

	if (cur_ops->sync && !(++n & 0xfff))
		cur_ops->sync();
}

static int __init
rcu_torture_init(void)
{
	long i;
	int cpu;
	int firsterr = 0;
	static struct rcu_torture_ops *torture_ops[] = {
		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
		&busted_srcud_ops, &tasks_ops,
	};

	if (!torture_init_begin(torture_type, verbose))
		return -EBUSY;

	/* Process args and tell the world that the torturer is on the job. */
	for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
		cur_ops = torture_ops[i];
		if (strcmp(torture_type, cur_ops->name) == 0)
			break;
	}
	if (i == ARRAY_SIZE(torture_ops)) {
		pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
			 torture_type);
		pr_alert("rcu-torture types:");
		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
			pr_cont(" %s", torture_ops[i]->name);
		pr_cont("\n");
		WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
		firsterr = -EINVAL;
		cur_ops = NULL;
		goto unwind;
	}
	if (cur_ops->fqs == NULL && fqs_duration != 0) {
		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
		fqs_duration = 0;
	}
	if (cur_ops->init)
		cur_ops->init();

	if (nreaders >= 0) {
		nrealreaders = nreaders;
	} else {
		nrealreaders = num_online_cpus() - 2 - nreaders;
		if (nrealreaders <= 0)
			nrealreaders = 1;
	}
	rcu_torture_print_module_parms(cur_ops, "Start of test");

	/* Set up the freelist. */

	INIT_LIST_HEAD(&rcu_torture_freelist);
	for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
		rcu_tortures[i].rtort_mbtest = 0;
		list_add_tail(&rcu_tortures[i].rtort_free,
			      &rcu_torture_freelist);
	}

	/* Initialize the statistics so that each run gets its own numbers. */

	rcu_torture_current = NULL;
	rcu_torture_current_version = 0;
	atomic_set(&n_rcu_torture_alloc, 0);
	atomic_set(&n_rcu_torture_alloc_fail, 0);
	atomic_set(&n_rcu_torture_free, 0);
	atomic_set(&n_rcu_torture_mberror, 0);
	atomic_set(&n_rcu_torture_error, 0);
	n_rcu_torture_barrier_error = 0;
	n_rcu_torture_boost_ktrerror = 0;
	n_rcu_torture_boost_rterror = 0;
	n_rcu_torture_boost_failure = 0;
	n_rcu_torture_boosts = 0;
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
		atomic_set(&rcu_torture_wcount[i], 0);
	for_each_possible_cpu(cpu) {
		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
			per_cpu(rcu_torture_count, cpu)[i] = 0;
			per_cpu(rcu_torture_batch, cpu)[i] = 0;
		}
	}
	err_segs_recorded = 0;
	rt_read_nsegs = 0;

	/* Start up the kthreads. */

	firsterr = torture_create_kthread(rcu_torture_writer, NULL,
					  writer_task);
	if (firsterr)
		goto unwind;
	if (nfakewriters > 0) {
		fakewriter_tasks = kcalloc(nfakewriters,
					   sizeof(fakewriter_tasks[0]),
					   GFP_KERNEL);
		if (fakewriter_tasks == NULL) {
			VERBOSE_TOROUT_ERRSTRING("out of memory");
			firsterr = -ENOMEM;
			goto unwind;
		}
	}
	for (i = 0; i < nfakewriters; i++) {
		firsterr = torture_create_kthread(rcu_torture_fakewriter,
						  NULL, fakewriter_tasks[i]);
		if (firsterr)
			goto unwind;
	}
	reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
			       GFP_KERNEL);
	if (reader_tasks == NULL) {
		VERBOSE_TOROUT_ERRSTRING("out of memory");
		firsterr = -ENOMEM;
		goto unwind;
	}
	for (i = 0; i < nrealreaders; i++) {
		firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
						  reader_tasks[i]);
		if (firsterr)
			goto unwind;
	}
	if (stat_interval > 0) {
		firsterr = torture_create_kthread(rcu_torture_stats, NULL,
						  stats_task);
		if (firsterr)
			goto unwind;
	}
	if (test_no_idle_hz && shuffle_interval > 0) {
		firsterr = torture_shuffle_init(shuffle_interval * HZ);
		if (firsterr)
			goto unwind;
	}
	if (stutter < 0)
		stutter = 0;
	if (stutter) {
		firsterr = torture_stutter_init(stutter * HZ);
		if (firsterr)
			goto unwind;
	}
	if (fqs_duration < 0)
		fqs_duration = 0;
	if (fqs_duration) {
		/* Create the fqs thread */
		firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
						  fqs_task);
		if (firsterr)
			goto unwind;
	}
	if (test_boost_interval < 1)
		test_boost_interval = 1;
	if (test_boost_duration < 2)
		test_boost_duration = 2;
	if (rcu_torture_can_boost()) {

		boost_starttime = jiffies + test_boost_interval * HZ;

		firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
					     rcutorture_booster_init,
					     rcutorture_booster_cleanup);
		if (firsterr < 0)
			goto unwind;
		rcutor_hp = firsterr;
	}
	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
	if (firsterr)
		goto unwind;
	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
				      rcutorture_sync);
	if (firsterr)
		goto unwind;
	firsterr = rcu_torture_stall_init();
	if (firsterr)
		goto unwind;
	firsterr = rcu_torture_fwd_prog_init();
	if (firsterr)
		goto unwind;
	firsterr = rcu_torture_barrier_init();
	if (firsterr)
		goto unwind;
	if (object_debug)
		rcu_test_debug_objects();
	torture_init_end();
	return 0;

unwind:
	torture_init_end();
	rcu_torture_cleanup();
	return firsterr;
}

module_init(rcu_torture_init);
module_exit(rcu_torture_cleanup);