free electrons

Embedded Linux Experts

   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
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
/*
 * kernel/workqueue.c - generic async execution with shared worker pool
 *
 * Copyright (C) 2002		Ingo Molnar
 *
 *   Derived from the taskqueue/keventd code by:
 *     David Woodhouse <dwmw2@infradead.org>
 *     Andrew Morton
 *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
 *     Theodore Ts'o <tytso@mit.edu>
 *
 * Made to use alloc_percpu by Christoph Lameter.
 *
 * Copyright (C) 2010		SUSE Linux Products GmbH
 * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
 *
 * This is the generic async execution mechanism.  Work items as are
 * executed in process context.  The worker pool is shared and
 * automatically managed.  There are two worker pools for each CPU (one for
 * normal work items and the other for high priority ones) and some extra
 * pools for workqueues which are not bound to any specific CPU - the
 * number of these backing pools is dynamic.
 *
 * Please read Documentation/workqueue.txt for details.
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/completion.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/hardirq.h>
#include <linux/mempolicy.h>
#include <linux/freezer.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
#include <linux/lockdep.h>
#include <linux/idr.h>
#include <linux/jhash.h>
#include <linux/hashtable.h>
#include <linux/rculist.h>
#include <linux/nodemask.h>
#include <linux/moduleparam.h>
#include <linux/uaccess.h>

#include "workqueue_internal.h"

enum {
	/*
	 * worker_pool flags
	 *
	 * A bound pool is either associated or disassociated with its CPU.
	 * While associated (!DISASSOCIATED), all workers are bound to the
	 * CPU and none has %WORKER_UNBOUND set and concurrency management
	 * is in effect.
	 *
	 * While DISASSOCIATED, the cpu may be offline and all workers have
	 * %WORKER_UNBOUND set and concurrency management disabled, and may
	 * be executing on any CPU.  The pool behaves as an unbound one.
	 *
	 * Note that DISASSOCIATED should be flipped only while holding
	 * attach_mutex to avoid changing binding state while
	 * worker_attach_to_pool() is in progress.
	 */
	POOL_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */

	/* worker flags */
	WORKER_DIE		= 1 << 1,	/* die die die */
	WORKER_IDLE		= 1 << 2,	/* is idle */
	WORKER_PREP		= 1 << 3,	/* preparing to run works */
	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */
	WORKER_REBOUND		= 1 << 8,	/* worker was rebound */

	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_CPU_INTENSIVE |
				  WORKER_UNBOUND | WORKER_REBOUND,

	NR_STD_WORKER_POOLS	= 2,		/* # standard pools per cpu */

	UNBOUND_POOL_HASH_ORDER	= 6,		/* hashed by pool->attrs */
	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */

	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */

	MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
						/* call for help after 10ms
						   (min two ticks) */
	MAYDAY_INTERVAL		= HZ / 10,	/* and then every 100ms */
	CREATE_COOLDOWN		= HZ,		/* time to breath after fail */

	/*
	 * Rescue workers are used only on emergencies and shared by
	 * all cpus.  Give MIN_NICE.
	 */
	RESCUER_NICE_LEVEL	= MIN_NICE,
	HIGHPRI_NICE_LEVEL	= MIN_NICE,

	WQ_NAME_LEN		= 24,
};

/*
 * Structure fields follow one of the following exclusion rules.
 *
 * I: Modifiable by initialization/destruction paths and read-only for
 *    everyone else.
 *
 * P: Preemption protected.  Disabling preemption is enough and should
 *    only be modified and accessed from the local cpu.
 *
 * L: pool->lock protected.  Access with pool->lock held.
 *
 * X: During normal operation, modification requires pool->lock and should
 *    be done only from local cpu.  Either disabling preemption on local
 *    cpu or grabbing pool->lock is enough for read access.  If
 *    POOL_DISASSOCIATED is set, it's identical to L.
 *
 * A: pool->attach_mutex protected.
 *
 * PL: wq_pool_mutex protected.
 *
 * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.
 *
 * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
 *
 * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
 *      sched-RCU for reads.
 *
 * WQ: wq->mutex protected.
 *
 * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.
 *
 * MD: wq_mayday_lock protected.
 */

/* struct worker is defined in workqueue_internal.h */

struct worker_pool {
	spinlock_t		lock;		/* the pool lock */
	int			cpu;		/* I: the associated cpu */
	int			node;		/* I: the associated node ID */
	int			id;		/* I: pool ID */
	unsigned int		flags;		/* X: flags */

	unsigned long		watchdog_ts;	/* L: watchdog timestamp */

	struct list_head	worklist;	/* L: list of pending works */
	int			nr_workers;	/* L: total number of workers */

	/* nr_idle includes the ones off idle_list for rebinding */
	int			nr_idle;	/* L: currently idle ones */

	struct list_head	idle_list;	/* X: list of idle workers */
	struct timer_list	idle_timer;	/* L: worker idle timeout */
	struct timer_list	mayday_timer;	/* L: SOS timer for workers */

	/* a workers is either on busy_hash or idle_list, or the manager */
	DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
						/* L: hash of busy workers */

	/* see manage_workers() for details on the two manager mutexes */
	struct mutex		manager_arb;	/* manager arbitration */
	struct worker		*manager;	/* L: purely informational */
	struct mutex		attach_mutex;	/* attach/detach exclusion */
	struct list_head	workers;	/* A: attached workers */
	struct completion	*detach_completion; /* all workers detached */

	struct ida		worker_ida;	/* worker IDs for task name */

	struct workqueue_attrs	*attrs;		/* I: worker attributes */
	struct hlist_node	hash_node;	/* PL: unbound_pool_hash node */
	int			refcnt;		/* PL: refcnt for unbound pools */

	/*
	 * The current concurrency level.  As it's likely to be accessed
	 * from other CPUs during try_to_wake_up(), put it in a separate
	 * cacheline.
	 */
	atomic_t		nr_running ____cacheline_aligned_in_smp;

	/*
	 * Destruction of pool is sched-RCU protected to allow dereferences
	 * from get_work_pool().
	 */
	struct rcu_head		rcu;
} ____cacheline_aligned_in_smp;

/*
 * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
 * of work_struct->data are used for flags and the remaining high bits
 * point to the pwq; thus, pwqs need to be aligned at two's power of the
 * number of flag bits.
 */
struct pool_workqueue {
	struct worker_pool	*pool;		/* I: the associated pool */
	struct workqueue_struct *wq;		/* I: the owning workqueue */
	int			work_color;	/* L: current color */
	int			flush_color;	/* L: flushing color */
	int			refcnt;		/* L: reference count */
	int			nr_in_flight[WORK_NR_COLORS];
						/* L: nr of in_flight works */
	int			nr_active;	/* L: nr of active works */
	int			max_active;	/* L: max active works */
	struct list_head	delayed_works;	/* L: delayed works */
	struct list_head	pwqs_node;	/* WR: node on wq->pwqs */
	struct list_head	mayday_node;	/* MD: node on wq->maydays */

	/*
	 * Release of unbound pwq is punted to system_wq.  See put_pwq()
	 * and pwq_unbound_release_workfn() for details.  pool_workqueue
	 * itself is also sched-RCU protected so that the first pwq can be
	 * determined without grabbing wq->mutex.
	 */
	struct work_struct	unbound_release_work;
	struct rcu_head		rcu;
} __aligned(1 << WORK_STRUCT_FLAG_BITS);

/*
 * Structure used to wait for workqueue flush.
 */
struct wq_flusher {
	struct list_head	list;		/* WQ: list of flushers */
	int			flush_color;	/* WQ: flush color waiting for */
	struct completion	done;		/* flush completion */
};

struct wq_device;

/*
 * The externally visible workqueue.  It relays the issued work items to
 * the appropriate worker_pool through its pool_workqueues.
 */
struct workqueue_struct {
	struct list_head	pwqs;		/* WR: all pwqs of this wq */
	struct list_head	list;		/* PR: list of all workqueues */

	struct mutex		mutex;		/* protects this wq */
	int			work_color;	/* WQ: current work color */
	int			flush_color;	/* WQ: current flush color */
	atomic_t		nr_pwqs_to_flush; /* flush in progress */
	struct wq_flusher	*first_flusher;	/* WQ: first flusher */
	struct list_head	flusher_queue;	/* WQ: flush waiters */
	struct list_head	flusher_overflow; /* WQ: flush overflow list */

	struct list_head	maydays;	/* MD: pwqs requesting rescue */
	struct worker		*rescuer;	/* I: rescue worker */

	int			nr_drainers;	/* WQ: drain in progress */
	int			saved_max_active; /* WQ: saved pwq max_active */

	struct workqueue_attrs	*unbound_attrs;	/* PW: only for unbound wqs */
	struct pool_workqueue	*dfl_pwq;	/* PW: only for unbound wqs */

#ifdef CONFIG_SYSFS
	struct wq_device	*wq_dev;	/* I: for sysfs interface */
#endif
#ifdef CONFIG_LOCKDEP
	struct lockdep_map	lockdep_map;
#endif
	char			name[WQ_NAME_LEN]; /* I: workqueue name */

	/*
	 * Destruction of workqueue_struct is sched-RCU protected to allow
	 * walking the workqueues list without grabbing wq_pool_mutex.
	 * This is used to dump all workqueues from sysrq.
	 */
	struct rcu_head		rcu;

	/* hot fields used during command issue, aligned to cacheline */
	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
	struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
	struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
};

static struct kmem_cache *pwq_cache;

static cpumask_var_t *wq_numa_possible_cpumask;
					/* possible CPUs of each node */

static bool wq_disable_numa;
module_param_named(disable_numa, wq_disable_numa, bool, 0444);

/* see the comment above the definition of WQ_POWER_EFFICIENT */
static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
module_param_named(power_efficient, wq_power_efficient, bool, 0444);

static bool wq_online;			/* can kworkers be created yet? */

static bool wq_numa_enabled;		/* unbound NUMA affinity enabled */

/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;

static DEFINE_MUTEX(wq_pool_mutex);	/* protects pools and workqueues list */
static DEFINE_SPINLOCK(wq_mayday_lock);	/* protects wq->maydays list */

static LIST_HEAD(workqueues);		/* PR: list of all workqueues */
static bool workqueue_freezing;		/* PL: have wqs started freezing? */

/* PL: allowable cpus for unbound wqs and work items */
static cpumask_var_t wq_unbound_cpumask;

/* CPU where unbound work was last round robin scheduled from this CPU */
static DEFINE_PER_CPU(int, wq_rr_cpu_last);

/*
 * Local execution of unbound work items is no longer guaranteed.  The
 * following always forces round-robin CPU selection on unbound work items
 * to uncover usages which depend on it.
 */
#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
static bool wq_debug_force_rr_cpu = true;
#else
static bool wq_debug_force_rr_cpu = false;
#endif
module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);

/* the per-cpu worker pools */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);

static DEFINE_IDR(worker_pool_idr);	/* PR: idr of all pools */

/* PL: hash of all unbound pools keyed by pool->attrs */
static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);

/* I: attributes used when instantiating standard unbound pools on demand */
static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];

/* I: attributes used when instantiating ordered pools on demand */
static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];

struct workqueue_struct *system_wq __read_mostly;
EXPORT_SYMBOL(system_wq);
struct workqueue_struct *system_highpri_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_highpri_wq);
struct workqueue_struct *system_long_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_long_wq);
struct workqueue_struct *system_unbound_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_unbound_wq);
struct workqueue_struct *system_freezable_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_freezable_wq);
struct workqueue_struct *system_power_efficient_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_power_efficient_wq);
struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);

static int worker_thread(void *__worker);
static void workqueue_sysfs_unregister(struct workqueue_struct *wq);

#define CREATE_TRACE_POINTS
#include <trace/events/workqueue.h>

#define assert_rcu_or_pool_mutex()					\
	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\
			 !lockdep_is_held(&wq_pool_mutex),		\
			 "sched RCU or wq_pool_mutex should be held")

#define assert_rcu_or_wq_mutex(wq)					\
	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\
			 !lockdep_is_held(&wq->mutex),			\
			 "sched RCU or wq->mutex should be held")

#define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&			\
			 !lockdep_is_held(&wq->mutex) &&		\
			 !lockdep_is_held(&wq_pool_mutex),		\
			 "sched RCU, wq->mutex or wq_pool_mutex should be held")

#define for_each_cpu_worker_pool(pool, cpu)				\
	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\
	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
	     (pool)++)

/**
 * for_each_pool - iterate through all worker_pools in the system
 * @pool: iteration cursor
 * @pi: integer used for iteration
 *
 * This must be called either with wq_pool_mutex held or sched RCU read
 * locked.  If the pool needs to be used beyond the locking in effect, the
 * caller is responsible for guaranteeing that the pool stays online.
 *
 * The if/else clause exists only for the lockdep assertion and can be
 * ignored.
 */
#define for_each_pool(pool, pi)						\
	idr_for_each_entry(&worker_pool_idr, pool, pi)			\
		if (({ assert_rcu_or_pool_mutex(); false; })) { }	\
		else

/**
 * for_each_pool_worker - iterate through all workers of a worker_pool
 * @worker: iteration cursor
 * @pool: worker_pool to iterate workers of
 *
 * This must be called with @pool->attach_mutex.
 *
 * The if/else clause exists only for the lockdep assertion and can be
 * ignored.
 */
#define for_each_pool_worker(worker, pool)				\
	list_for_each_entry((worker), &(pool)->workers, node)		\
		if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
		else

/**
 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
 * @pwq: iteration cursor
 * @wq: the target workqueue
 *
 * This must be called either with wq->mutex held or sched RCU read locked.
 * If the pwq needs to be used beyond the locking in effect, the caller is
 * responsible for guaranteeing that the pwq stays online.
 *
 * The if/else clause exists only for the lockdep assertion and can be
 * ignored.
 */
#define for_each_pwq(pwq, wq)						\
	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
		if (({ assert_rcu_or_wq_mutex(wq); false; })) { }	\
		else

#ifdef CONFIG_DEBUG_OBJECTS_WORK

static struct debug_obj_descr work_debug_descr;

static void *work_debug_hint(void *addr)
{
	return ((struct work_struct *) addr)->func;
}

static bool work_is_static_object(void *addr)
{
	struct work_struct *work = addr;

	return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
}

/*
 * fixup_init is called when:
 * - an active object is initialized
 */
static bool work_fixup_init(void *addr, enum debug_obj_state state)
{
	struct work_struct *work = addr;

	switch (state) {
	case ODEBUG_STATE_ACTIVE:
		cancel_work_sync(work);
		debug_object_init(work, &work_debug_descr);
		return true;
	default:
		return false;
	}
}

/*
 * fixup_free is called when:
 * - an active object is freed
 */
static bool work_fixup_free(void *addr, enum debug_obj_state state)
{
	struct work_struct *work = addr;

	switch (state) {
	case ODEBUG_STATE_ACTIVE:
		cancel_work_sync(work);
		debug_object_free(work, &work_debug_descr);
		return true;
	default:
		return false;
	}
}

static struct debug_obj_descr work_debug_descr = {
	.name		= "work_struct",
	.debug_hint	= work_debug_hint,
	.is_static_object = work_is_static_object,
	.fixup_init	= work_fixup_init,
	.fixup_free	= work_fixup_free,
};

static inline void debug_work_activate(struct work_struct *work)
{
	debug_object_activate(work, &work_debug_descr);
}

static inline void debug_work_deactivate(struct work_struct *work)
{
	debug_object_deactivate(work, &work_debug_descr);
}

void __init_work(struct work_struct *work, int onstack)
{
	if (onstack)
		debug_object_init_on_stack(work, &work_debug_descr);
	else
		debug_object_init(work, &work_debug_descr);
}
EXPORT_SYMBOL_GPL(__init_work);

void destroy_work_on_stack(struct work_struct *work)
{
	debug_object_free(work, &work_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_work_on_stack);

void destroy_delayed_work_on_stack(struct delayed_work *work)
{
	destroy_timer_on_stack(&work->timer);
	debug_object_free(&work->work, &work_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);

#else
static inline void debug_work_activate(struct work_struct *work) { }
static inline void debug_work_deactivate(struct work_struct *work) { }
#endif

/**
 * worker_pool_assign_id - allocate ID and assing it to @pool
 * @pool: the pool pointer of interest
 *
 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
 * successfully, -errno on failure.
 */
static int worker_pool_assign_id(struct worker_pool *pool)
{
	int ret;

	lockdep_assert_held(&wq_pool_mutex);

	ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
			GFP_KERNEL);
	if (ret >= 0) {
		pool->id = ret;
		return 0;
	}
	return ret;
}

/**
 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
 * @wq: the target workqueue
 * @node: the node ID
 *
 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
 * read locked.
 * If the pwq needs to be used beyond the locking in effect, the caller is
 * responsible for guaranteeing that the pwq stays online.
 *
 * Return: The unbound pool_workqueue for @node.
 */
static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
						  int node)
{
	assert_rcu_or_wq_mutex_or_pool_mutex(wq);

	/*
	 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
	 * delayed item is pending.  The plan is to keep CPU -> NODE
	 * mapping valid and stable across CPU on/offlines.  Once that
	 * happens, this workaround can be removed.
	 */
	if (unlikely(node == NUMA_NO_NODE))
		return wq->dfl_pwq;

	return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
}

static unsigned int work_color_to_flags(int color)
{
	return color << WORK_STRUCT_COLOR_SHIFT;
}

static int get_work_color(struct work_struct *work)
{
	return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
		((1 << WORK_STRUCT_COLOR_BITS) - 1);
}

static int work_next_color(int color)
{
	return (color + 1) % WORK_NR_COLORS;
}

/*
 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
 * contain the pointer to the queued pwq.  Once execution starts, the flag
 * is cleared and the high bits contain OFFQ flags and pool ID.
 *
 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
 * and clear_work_data() can be used to set the pwq, pool or clear
 * work->data.  These functions should only be called while the work is
 * owned - ie. while the PENDING bit is set.
 *
 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
 * corresponding to a work.  Pool is available once the work has been
 * queued anywhere after initialization until it is sync canceled.  pwq is
 * available only while the work item is queued.
 *
 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
 * canceled.  While being canceled, a work item may have its PENDING set
 * but stay off timer and worklist for arbitrarily long and nobody should
 * try to steal the PENDING bit.
 */
static inline void set_work_data(struct work_struct *work, unsigned long data,
				 unsigned long flags)
{
	WARN_ON_ONCE(!work_pending(work));
	atomic_long_set(&work->data, data | flags | work_static(work));
}

static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
			 unsigned long extra_flags)
{
	set_work_data(work, (unsigned long)pwq,
		      WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
}

static void set_work_pool_and_keep_pending(struct work_struct *work,
					   int pool_id)
{
	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
		      WORK_STRUCT_PENDING);
}

static void set_work_pool_and_clear_pending(struct work_struct *work,
					    int pool_id)
{
	/*
	 * The following wmb is paired with the implied mb in
	 * test_and_set_bit(PENDING) and ensures all updates to @work made
	 * here are visible to and precede any updates by the next PENDING
	 * owner.
	 */
	smp_wmb();
	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
	/*
	 * The following mb guarantees that previous clear of a PENDING bit
	 * will not be reordered with any speculative LOADS or STORES from
	 * work->current_func, which is executed afterwards.  This possible
	 * reordering can lead to a missed execution on attempt to qeueue
	 * the same @work.  E.g. consider this case:
	 *
	 *   CPU#0                         CPU#1
	 *   ----------------------------  --------------------------------
	 *
	 * 1  STORE event_indicated
	 * 2  queue_work_on() {
	 * 3    test_and_set_bit(PENDING)
	 * 4 }                             set_..._and_clear_pending() {
	 * 5                                 set_work_data() # clear bit
	 * 6                                 smp_mb()
	 * 7                               work->current_func() {
	 * 8				      LOAD event_indicated
	 *				   }
	 *
	 * Without an explicit full barrier speculative LOAD on line 8 can
	 * be executed before CPU#0 does STORE on line 1.  If that happens,
	 * CPU#0 observes the PENDING bit is still set and new execution of
	 * a @work is not queued in a hope, that CPU#1 will eventually
	 * finish the queued @work.  Meanwhile CPU#1 does not see
	 * event_indicated is set, because speculative LOAD was executed
	 * before actual STORE.
	 */
	smp_mb();
}

static void clear_work_data(struct work_struct *work)
{
	smp_wmb();	/* see set_work_pool_and_clear_pending() */
	set_work_data(work, WORK_STRUCT_NO_POOL, 0);
}

static struct pool_workqueue *get_work_pwq(struct work_struct *work)
{
	unsigned long data = atomic_long_read(&work->data);

	if (data & WORK_STRUCT_PWQ)
		return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
	else
		return NULL;
}

/**
 * get_work_pool - return the worker_pool a given work was associated with
 * @work: the work item of interest
 *
 * Pools are created and destroyed under wq_pool_mutex, and allows read
 * access under sched-RCU read lock.  As such, this function should be
 * called under wq_pool_mutex or with preemption disabled.
 *
 * All fields of the returned pool are accessible as long as the above
 * mentioned locking is in effect.  If the returned pool needs to be used
 * beyond the critical section, the caller is responsible for ensuring the
 * returned pool is and stays online.
 *
 * Return: The worker_pool @work was last associated with.  %NULL if none.
 */
static struct worker_pool *get_work_pool(struct work_struct *work)
{
	unsigned long data = atomic_long_read(&work->data);
	int pool_id;

	assert_rcu_or_pool_mutex();

	if (data & WORK_STRUCT_PWQ)
		return ((struct pool_workqueue *)
			(data & WORK_STRUCT_WQ_DATA_MASK))->pool;

	pool_id = data >> WORK_OFFQ_POOL_SHIFT;
	if (pool_id == WORK_OFFQ_POOL_NONE)
		return NULL;

	return idr_find(&worker_pool_idr, pool_id);
}

/**
 * get_work_pool_id - return the worker pool ID a given work is associated with
 * @work: the work item of interest
 *
 * Return: The worker_pool ID @work was last associated with.
 * %WORK_OFFQ_POOL_NONE if none.
 */
static int get_work_pool_id(struct work_struct *work)
{
	unsigned long data = atomic_long_read(&work->data);

	if (data & WORK_STRUCT_PWQ)
		return ((struct pool_workqueue *)
			(data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;

	return data >> WORK_OFFQ_POOL_SHIFT;
}

static void mark_work_canceling(struct work_struct *work)
{
	unsigned long pool_id = get_work_pool_id(work);

	pool_id <<= WORK_OFFQ_POOL_SHIFT;
	set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
}

static bool work_is_canceling(struct work_struct *work)
{
	unsigned long data = atomic_long_read(&work->data);

	return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
}

/*
 * Policy functions.  These define the policies on how the global worker
 * pools are managed.  Unless noted otherwise, these functions assume that
 * they're being called with pool->lock held.
 */

static bool __need_more_worker(struct worker_pool *pool)
{
	return !atomic_read(&pool->nr_running);
}

/*
 * Need to wake up a worker?  Called from anything but currently
 * running workers.
 *
 * Note that, because unbound workers never contribute to nr_running, this
 * function will always return %true for unbound pools as long as the
 * worklist isn't empty.
 */
static bool need_more_worker(struct worker_pool *pool)
{
	return !list_empty(&pool->worklist) && __need_more_worker(pool);
}

/* Can I start working?  Called from busy but !running workers. */
static bool may_start_working(struct worker_pool *pool)
{
	return pool->nr_idle;
}

/* Do I need to keep working?  Called from currently running workers. */
static bool keep_working(struct worker_pool *pool)
{
	return !list_empty(&pool->worklist) &&
		atomic_read(&pool->nr_running) <= 1;
}

/* Do we need a new worker?  Called from manager. */
static bool need_to_create_worker(struct worker_pool *pool)
{
	return need_more_worker(pool) && !may_start_working(pool);
}

/* Do we have too many workers and should some go away? */
static bool too_many_workers(struct worker_pool *pool)
{
	bool managing = mutex_is_locked(&pool->manager_arb);
	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
	int nr_busy = pool->nr_workers - nr_idle;

	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
}

/*
 * Wake up functions.
 */

/* Return the first idle worker.  Safe with preemption disabled */
static struct worker *first_idle_worker(struct worker_pool *pool)
{
	if (unlikely(list_empty(&pool->idle_list)))
		return NULL;

	return list_first_entry(&pool->idle_list, struct worker, entry);
}

/**
 * wake_up_worker - wake up an idle worker
 * @pool: worker pool to wake worker from
 *
 * Wake up the first idle worker of @pool.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 */
static void wake_up_worker(struct worker_pool *pool)
{
	struct worker *worker = first_idle_worker(pool);

	if (likely(worker))
		wake_up_process(worker->task);
}

/**
 * wq_worker_waking_up - a worker is waking up
 * @task: task waking up
 * @cpu: CPU @task is waking up to
 *
 * This function is called during try_to_wake_up() when a worker is
 * being awoken.
 *
 * CONTEXT:
 * spin_lock_irq(rq->lock)
 */
void wq_worker_waking_up(struct task_struct *task, int cpu)
{
	struct worker *worker = kthread_data(task);

	if (!(worker->flags & WORKER_NOT_RUNNING)) {
		WARN_ON_ONCE(worker->pool->cpu != cpu);
		atomic_inc(&worker->pool->nr_running);
	}
}

/**
 * wq_worker_sleeping - a worker is going to sleep
 * @task: task going to sleep
 *
 * This function is called during schedule() when a busy worker is
 * going to sleep.  Worker on the same cpu can be woken up by
 * returning pointer to its task.
 *
 * CONTEXT:
 * spin_lock_irq(rq->lock)
 *
 * Return:
 * Worker task on @cpu to wake up, %NULL if none.
 */
struct task_struct *wq_worker_sleeping(struct task_struct *task)
{
	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
	struct worker_pool *pool;

	/*
	 * Rescuers, which may not have all the fields set up like normal
	 * workers, also reach here, let's not access anything before
	 * checking NOT_RUNNING.
	 */
	if (worker->flags & WORKER_NOT_RUNNING)
		return NULL;

	pool = worker->pool;

	/* this can only happen on the local cpu */
	if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
		return NULL;

	/*
	 * The counterpart of the following dec_and_test, implied mb,
	 * worklist not empty test sequence is in insert_work().
	 * Please read comment there.
	 *
	 * NOT_RUNNING is clear.  This means that we're bound to and
	 * running on the local cpu w/ rq lock held and preemption
	 * disabled, which in turn means that none else could be
	 * manipulating idle_list, so dereferencing idle_list without pool
	 * lock is safe.
	 */
	if (atomic_dec_and_test(&pool->nr_running) &&
	    !list_empty(&pool->worklist))
		to_wakeup = first_idle_worker(pool);
	return to_wakeup ? to_wakeup->task : NULL;
}

/**
 * worker_set_flags - set worker flags and adjust nr_running accordingly
 * @worker: self
 * @flags: flags to set
 *
 * Set @flags in @worker->flags and adjust nr_running accordingly.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock)
 */
static inline void worker_set_flags(struct worker *worker, unsigned int flags)
{
	struct worker_pool *pool = worker->pool;

	WARN_ON_ONCE(worker->task != current);

	/* If transitioning into NOT_RUNNING, adjust nr_running. */
	if ((flags & WORKER_NOT_RUNNING) &&
	    !(worker->flags & WORKER_NOT_RUNNING)) {
		atomic_dec(&pool->nr_running);
	}

	worker->flags |= flags;
}

/**
 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
 * @worker: self
 * @flags: flags to clear
 *
 * Clear @flags in @worker->flags and adjust nr_running accordingly.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock)
 */
static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
{
	struct worker_pool *pool = worker->pool;
	unsigned int oflags = worker->flags;

	WARN_ON_ONCE(worker->task != current);

	worker->flags &= ~flags;

	/*
	 * If transitioning out of NOT_RUNNING, increment nr_running.  Note
	 * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
	 * of multiple flags, not a single flag.
	 */
	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
		if (!(worker->flags & WORKER_NOT_RUNNING))
			atomic_inc(&pool->nr_running);
}

/**
 * find_worker_executing_work - find worker which is executing a work
 * @pool: pool of interest
 * @work: work to find worker for
 *
 * Find a worker which is executing @work on @pool by searching
 * @pool->busy_hash which is keyed by the address of @work.  For a worker
 * to match, its current execution should match the address of @work and
 * its work function.  This is to avoid unwanted dependency between
 * unrelated work executions through a work item being recycled while still
 * being executed.
 *
 * This is a bit tricky.  A work item may be freed once its execution
 * starts and nothing prevents the freed area from being recycled for
 * another work item.  If the same work item address ends up being reused
 * before the original execution finishes, workqueue will identify the
 * recycled work item as currently executing and make it wait until the
 * current execution finishes, introducing an unwanted dependency.
 *
 * This function checks the work item address and work function to avoid
 * false positives.  Note that this isn't complete as one may construct a
 * work function which can introduce dependency onto itself through a
 * recycled work item.  Well, if somebody wants to shoot oneself in the
 * foot that badly, there's only so much we can do, and if such deadlock
 * actually occurs, it should be easy to locate the culprit work function.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 *
 * Return:
 * Pointer to worker which is executing @work if found, %NULL
 * otherwise.
 */
static struct worker *find_worker_executing_work(struct worker_pool *pool,
						 struct work_struct *work)
{
	struct worker *worker;

	hash_for_each_possible(pool->busy_hash, worker, hentry,
			       (unsigned long)work)
		if (worker->current_work == work &&
		    worker->current_func == work->func)
			return worker;

	return NULL;
}

/**
 * move_linked_works - move linked works to a list
 * @work: start of series of works to be scheduled
 * @head: target list to append @work to
 * @nextp: out parameter for nested worklist walking
 *
 * Schedule linked works starting from @work to @head.  Work series to
 * be scheduled starts at @work and includes any consecutive work with
 * WORK_STRUCT_LINKED set in its predecessor.
 *
 * If @nextp is not NULL, it's updated to point to the next work of
 * the last scheduled work.  This allows move_linked_works() to be
 * nested inside outer list_for_each_entry_safe().
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 */
static void move_linked_works(struct work_struct *work, struct list_head *head,
			      struct work_struct **nextp)
{
	struct work_struct *n;

	/*
	 * Linked worklist will always end before the end of the list,
	 * use NULL for list head.
	 */
	list_for_each_entry_safe_from(work, n, NULL, entry) {
		list_move_tail(&work->entry, head);
		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
			break;
	}

	/*
	 * If we're already inside safe list traversal and have moved
	 * multiple works to the scheduled queue, the next position
	 * needs to be updated.
	 */
	if (nextp)
		*nextp = n;
}

/**
 * get_pwq - get an extra reference on the specified pool_workqueue
 * @pwq: pool_workqueue to get
 *
 * Obtain an extra reference on @pwq.  The caller should guarantee that
 * @pwq has positive refcnt and be holding the matching pool->lock.
 */
static void get_pwq(struct pool_workqueue *pwq)
{
	lockdep_assert_held(&pwq->pool->lock);
	WARN_ON_ONCE(pwq->refcnt <= 0);
	pwq->refcnt++;
}

/**
 * put_pwq - put a pool_workqueue reference
 * @pwq: pool_workqueue to put
 *
 * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
 * destruction.  The caller should be holding the matching pool->lock.
 */
static void put_pwq(struct pool_workqueue *pwq)
{
	lockdep_assert_held(&pwq->pool->lock);
	if (likely(--pwq->refcnt))
		return;
	if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
		return;
	/*
	 * @pwq can't be released under pool->lock, bounce to
	 * pwq_unbound_release_workfn().  This never recurses on the same
	 * pool->lock as this path is taken only for unbound workqueues and
	 * the release work item is scheduled on a per-cpu workqueue.  To
	 * avoid lockdep warning, unbound pool->locks are given lockdep
	 * subclass of 1 in get_unbound_pool().
	 */
	schedule_work(&pwq->unbound_release_work);
}

/**
 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
 * @pwq: pool_workqueue to put (can be %NULL)
 *
 * put_pwq() with locking.  This function also allows %NULL @pwq.
 */
static void put_pwq_unlocked(struct pool_workqueue *pwq)
{
	if (pwq) {
		/*
		 * As both pwqs and pools are sched-RCU protected, the
		 * following lock operations are safe.
		 */
		spin_lock_irq(&pwq->pool->lock);
		put_pwq(pwq);
		spin_unlock_irq(&pwq->pool->lock);
	}
}

static void pwq_activate_delayed_work(struct work_struct *work)
{
	struct pool_workqueue *pwq = get_work_pwq(work);

	trace_workqueue_activate_work(work);
	if (list_empty(&pwq->pool->worklist))
		pwq->pool->watchdog_ts = jiffies;
	move_linked_works(work, &pwq->pool->worklist, NULL);
	__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
	pwq->nr_active++;
}

static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
{
	struct work_struct *work = list_first_entry(&pwq->delayed_works,
						    struct work_struct, entry);

	pwq_activate_delayed_work(work);
}

/**
 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
 * @pwq: pwq of interest
 * @color: color of work which left the queue
 *
 * A work either has completed or is removed from pending queue,
 * decrement nr_in_flight of its pwq and handle workqueue flushing.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 */
static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
{
	/* uncolored work items don't participate in flushing or nr_active */
	if (color == WORK_NO_COLOR)
		goto out_put;

	pwq->nr_in_flight[color]--;

	pwq->nr_active--;
	if (!list_empty(&pwq->delayed_works)) {
		/* one down, submit a delayed one */
		if (pwq->nr_active < pwq->max_active)
			pwq_activate_first_delayed(pwq);
	}

	/* is flush in progress and are we at the flushing tip? */
	if (likely(pwq->flush_color != color))
		goto out_put;

	/* are there still in-flight works? */
	if (pwq->nr_in_flight[color])
		goto out_put;

	/* this pwq is done, clear flush_color */
	pwq->flush_color = -1;

	/*
	 * If this was the last pwq, wake up the first flusher.  It
	 * will handle the rest.
	 */
	if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
		complete(&pwq->wq->first_flusher->done);
out_put:
	put_pwq(pwq);
}

/**
 * try_to_grab_pending - steal work item from worklist and disable irq
 * @work: work item to steal
 * @is_dwork: @work is a delayed_work
 * @flags: place to store irq state
 *
 * Try to grab PENDING bit of @work.  This function can handle @work in any
 * stable state - idle, on timer or on worklist.
 *
 * Return:
 *  1		if @work was pending and we successfully stole PENDING
 *  0		if @work was idle and we claimed PENDING
 *  -EAGAIN	if PENDING couldn't be grabbed at the moment, safe to busy-retry
 *  -ENOENT	if someone else is canceling @work, this state may persist
 *		for arbitrarily long
 *
 * Note:
 * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
 * interrupted while holding PENDING and @work off queue, irq must be
 * disabled on entry.  This, combined with delayed_work->timer being
 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
 *
 * On successful return, >= 0, irq is disabled and the caller is
 * responsible for releasing it using local_irq_restore(*@flags).
 *
 * This function is safe to call from any context including IRQ handler.
 */
static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
			       unsigned long *flags)
{
	struct worker_pool *pool;
	struct pool_workqueue *pwq;

	local_irq_save(*flags);

	/* try to steal the timer if it exists */
	if (is_dwork) {
		struct delayed_work *dwork = to_delayed_work(work);

		/*
		 * dwork->timer is irqsafe.  If del_timer() fails, it's
		 * guaranteed that the timer is not queued anywhere and not
		 * running on the local CPU.
		 */
		if (likely(del_timer(&dwork->timer)))
			return 1;
	}

	/* try to claim PENDING the normal way */
	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
		return 0;

	/*
	 * The queueing is in progress, or it is already queued. Try to
	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
	 */
	pool = get_work_pool(work);
	if (!pool)
		goto fail;

	spin_lock(&pool->lock);
	/*
	 * work->data is guaranteed to point to pwq only while the work
	 * item is queued on pwq->wq, and both updating work->data to point
	 * to pwq on queueing and to pool on dequeueing are done under
	 * pwq->pool->lock.  This in turn guarantees that, if work->data
	 * points to pwq which is associated with a locked pool, the work
	 * item is currently queued on that pool.
	 */
	pwq = get_work_pwq(work);
	if (pwq && pwq->pool == pool) {
		debug_work_deactivate(work);

		/*
		 * A delayed work item cannot be grabbed directly because
		 * it might have linked NO_COLOR work items which, if left
		 * on the delayed_list, will confuse pwq->nr_active
		 * management later on and cause stall.  Make sure the work
		 * item is activated before grabbing.
		 */
		if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
			pwq_activate_delayed_work(work);

		list_del_init(&work->entry);
		pwq_dec_nr_in_flight(pwq, get_work_color(work));

		/* work->data points to pwq iff queued, point to pool */
		set_work_pool_and_keep_pending(work, pool->id);

		spin_unlock(&pool->lock);
		return 1;
	}
	spin_unlock(&pool->lock);
fail:
	local_irq_restore(*flags);
	if (work_is_canceling(work))
		return -ENOENT;
	cpu_relax();
	return -EAGAIN;
}

/**
 * insert_work - insert a work into a pool
 * @pwq: pwq @work belongs to
 * @work: work to insert
 * @head: insertion point
 * @extra_flags: extra WORK_STRUCT_* flags to set
 *
 * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
 * work_struct flags.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 */
static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
			struct list_head *head, unsigned int extra_flags)
{
	struct worker_pool *pool = pwq->pool;

	/* we own @work, set data and link */
	set_work_pwq(work, pwq, extra_flags);
	list_add_tail(&work->entry, head);
	get_pwq(pwq);

	/*
	 * Ensure either wq_worker_sleeping() sees the above
	 * list_add_tail() or we see zero nr_running to avoid workers lying
	 * around lazily while there are works to be processed.
	 */
	smp_mb();

	if (__need_more_worker(pool))
		wake_up_worker(pool);
}

/*
 * Test whether @work is being queued from another work executing on the
 * same workqueue.
 */
static bool is_chained_work(struct workqueue_struct *wq)
{
	struct worker *worker;

	worker = current_wq_worker();
	/*
	 * Return %true iff I'm a worker execuing a work item on @wq.  If
	 * I'm @worker, it's safe to dereference it without locking.
	 */
	return worker && worker->current_pwq->wq == wq;
}

/*
 * When queueing an unbound work item to a wq, prefer local CPU if allowed
 * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
 * avoid perturbing sensitive tasks.
 */
static int wq_select_unbound_cpu(int cpu)
{
	static bool printed_dbg_warning;
	int new_cpu;

	if (likely(!wq_debug_force_rr_cpu)) {
		if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
			return cpu;
	} else if (!printed_dbg_warning) {
		pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
		printed_dbg_warning = true;
	}

	if (cpumask_empty(wq_unbound_cpumask))
		return cpu;

	new_cpu = __this_cpu_read(wq_rr_cpu_last);
	new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
	if (unlikely(new_cpu >= nr_cpu_ids)) {
		new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
		if (unlikely(new_cpu >= nr_cpu_ids))
			return cpu;
	}
	__this_cpu_write(wq_rr_cpu_last, new_cpu);

	return new_cpu;
}

static void __queue_work(int cpu, struct workqueue_struct *wq,
			 struct work_struct *work)
{
	struct pool_workqueue *pwq;
	struct worker_pool *last_pool;
	struct list_head *worklist;
	unsigned int work_flags;
	unsigned int req_cpu = cpu;

	/*
	 * While a work item is PENDING && off queue, a task trying to
	 * steal the PENDING will busy-loop waiting for it to either get
	 * queued or lose PENDING.  Grabbing PENDING and queueing should
	 * happen with IRQ disabled.
	 */
	WARN_ON_ONCE(!irqs_disabled());

	debug_work_activate(work);

	/* if draining, only works from the same workqueue are allowed */
	if (unlikely(wq->flags & __WQ_DRAINING) &&
	    WARN_ON_ONCE(!is_chained_work(wq)))
		return;
retry:
	if (req_cpu == WORK_CPU_UNBOUND)
		cpu = wq_select_unbound_cpu(raw_smp_processor_id());

	/* pwq which will be used unless @work is executing elsewhere */
	if (!(wq->flags & WQ_UNBOUND))
		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
	else
		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));

	/*
	 * If @work was previously on a different pool, it might still be
	 * running there, in which case the work needs to be queued on that
	 * pool to guarantee non-reentrancy.
	 */
	last_pool = get_work_pool(work);
	if (last_pool && last_pool != pwq->pool) {
		struct worker *worker;

		spin_lock(&last_pool->lock);

		worker = find_worker_executing_work(last_pool, work);

		if (worker && worker->current_pwq->wq == wq) {
			pwq = worker->current_pwq;
		} else {
			/* meh... not running there, queue here */
			spin_unlock(&last_pool->lock);
			spin_lock(&pwq->pool->lock);
		}
	} else {
		spin_lock(&pwq->pool->lock);
	}

	/*
	 * pwq is determined and locked.  For unbound pools, we could have
	 * raced with pwq release and it could already be dead.  If its
	 * refcnt is zero, repeat pwq selection.  Note that pwqs never die
	 * without another pwq replacing it in the numa_pwq_tbl or while
	 * work items are executing on it, so the retrying is guaranteed to
	 * make forward-progress.
	 */
	if (unlikely(!pwq->refcnt)) {
		if (wq->flags & WQ_UNBOUND) {
			spin_unlock(&pwq->pool->lock);
			cpu_relax();
			goto retry;
		}
		/* oops */
		WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
			  wq->name, cpu);
	}

	/* pwq determined, queue */
	trace_workqueue_queue_work(req_cpu, pwq, work);

	if (WARN_ON(!list_empty(&work->entry))) {
		spin_unlock(&pwq->pool->lock);
		return;
	}

	pwq->nr_in_flight[pwq->work_color]++;
	work_flags = work_color_to_flags(pwq->work_color);

	if (likely(pwq->nr_active < pwq->max_active)) {
		trace_workqueue_activate_work(work);
		pwq->nr_active++;
		worklist = &pwq->pool->worklist;
		if (list_empty(worklist))
			pwq->pool->watchdog_ts = jiffies;
	} else {
		work_flags |= WORK_STRUCT_DELAYED;
		worklist = &pwq->delayed_works;
	}

	insert_work(pwq, work, worklist, work_flags);

	spin_unlock(&pwq->pool->lock);
}

/**
 * queue_work_on - queue work on specific cpu
 * @cpu: CPU number to execute work on
 * @wq: workqueue to use
 * @work: work to queue
 *
 * We queue the work to a specific CPU, the caller must ensure it
 * can't go away.
 *
 * Return: %false if @work was already on a queue, %true otherwise.
 */
bool queue_work_on(int cpu, struct workqueue_struct *wq,
		   struct work_struct *work)
{
	bool ret = false;
	unsigned long flags;

	local_irq_save(flags);

	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
		__queue_work(cpu, wq, work);
		ret = true;
	}

	local_irq_restore(flags);
	return ret;
}
EXPORT_SYMBOL(queue_work_on);

void delayed_work_timer_fn(unsigned long __data)
{
	struct delayed_work *dwork = (struct delayed_work *)__data;

	/* should have been called from irqsafe timer with irq already off */
	__queue_work(dwork->cpu, dwork->wq, &dwork->work);
}
EXPORT_SYMBOL(delayed_work_timer_fn);

static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
				struct delayed_work *dwork, unsigned long delay)
{
	struct timer_list *timer = &dwork->timer;
	struct work_struct *work = &dwork->work;

	WARN_ON_ONCE(!wq);
	WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
		     timer->data != (unsigned long)dwork);
	WARN_ON_ONCE(timer_pending(timer));
	WARN_ON_ONCE(!list_empty(&work->entry));

	/*
	 * If @delay is 0, queue @dwork->work immediately.  This is for
	 * both optimization and correctness.  The earliest @timer can
	 * expire is on the closest next tick and delayed_work users depend
	 * on that there's no such delay when @delay is 0.
	 */
	if (!delay) {
		__queue_work(cpu, wq, &dwork->work);
		return;
	}

	dwork->wq = wq;
	dwork->cpu = cpu;
	timer->expires = jiffies + delay;

	if (unlikely(cpu != WORK_CPU_UNBOUND))
		add_timer_on(timer, cpu);
	else
		add_timer(timer);
}

/**
 * queue_delayed_work_on - queue work on specific CPU after delay
 * @cpu: CPU number to execute work on
 * @wq: workqueue to use
 * @dwork: work to queue
 * @delay: number of jiffies to wait before queueing
 *
 * Return: %false if @work was already on a queue, %true otherwise.  If
 * @delay is zero and @dwork is idle, it will be scheduled for immediate
 * execution.
 */
bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
			   struct delayed_work *dwork, unsigned long delay)
{
	struct work_struct *work = &dwork->work;
	bool ret = false;
	unsigned long flags;

	/* read the comment in __queue_work() */
	local_irq_save(flags);

	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
		__queue_delayed_work(cpu, wq, dwork, delay);
		ret = true;
	}

	local_irq_restore(flags);
	return ret;
}
EXPORT_SYMBOL(queue_delayed_work_on);

/**
 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
 * @cpu: CPU number to execute work on
 * @wq: workqueue to use
 * @dwork: work to queue
 * @delay: number of jiffies to wait before queueing
 *
 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
 * modify @dwork's timer so that it expires after @delay.  If @delay is
 * zero, @work is guaranteed to be scheduled immediately regardless of its
 * current state.
 *
 * Return: %false if @dwork was idle and queued, %true if @dwork was
 * pending and its timer was modified.
 *
 * This function is safe to call from any context including IRQ handler.
 * See try_to_grab_pending() for details.
 */
bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
			 struct delayed_work *dwork, unsigned long delay)
{
	unsigned long flags;
	int ret;

	do {
		ret = try_to_grab_pending(&dwork->work, true, &flags);
	} while (unlikely(ret == -EAGAIN));

	if (likely(ret >= 0)) {
		__queue_delayed_work(cpu, wq, dwork, delay);
		local_irq_restore(flags);
	}

	/* -ENOENT from try_to_grab_pending() becomes %true */
	return ret;
}
EXPORT_SYMBOL_GPL(mod_delayed_work_on);

/**
 * worker_enter_idle - enter idle state
 * @worker: worker which is entering idle state
 *
 * @worker is entering idle state.  Update stats and idle timer if
 * necessary.
 *
 * LOCKING:
 * spin_lock_irq(pool->lock).
 */
static void worker_enter_idle(struct worker *worker)
{
	struct worker_pool *pool = worker->pool;

	if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
	    WARN_ON_ONCE(!list_empty(&worker->entry) &&
			 (worker->hentry.next || worker->hentry.pprev)))
		return;

	/* can't use worker_set_flags(), also called from create_worker() */
	worker->flags |= WORKER_IDLE;
	pool->nr_idle++;
	worker->last_active = jiffies;

	/* idle_list is LIFO */
	list_add(&worker->entry, &pool->idle_list);

	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);

	/*
	 * Sanity check nr_running.  Because wq_unbind_fn() releases
	 * pool->lock between setting %WORKER_UNBOUND and zapping
	 * nr_running, the warning may trigger spuriously.  Check iff
	 * unbind is not in progress.
	 */
	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
		     pool->nr_workers == pool->nr_idle &&
		     atomic_read(&pool->nr_running));
}

/**
 * worker_leave_idle - leave idle state
 * @worker: worker which is leaving idle state
 *
 * @worker is leaving idle state.  Update stats.
 *
 * LOCKING:
 * spin_lock_irq(pool->lock).
 */
static void worker_leave_idle(struct worker *worker)
{
	struct worker_pool *pool = worker->pool;

	if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
		return;
	worker_clr_flags(worker, WORKER_IDLE);
	pool->nr_idle--;
	list_del_init(&worker->entry);
}

static struct worker *alloc_worker(int node)
{
	struct worker *worker;

	worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
	if (worker) {
		INIT_LIST_HEAD(&worker->entry);
		INIT_LIST_HEAD(&worker->scheduled);
		INIT_LIST_HEAD(&worker->node);
		/* on creation a worker is in !idle && prep state */
		worker->flags = WORKER_PREP;
	}
	return worker;
}

/**
 * worker_attach_to_pool() - attach a worker to a pool
 * @worker: worker to be attached
 * @pool: the target pool
 *
 * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
 * cpu-binding of @worker are kept coordinated with the pool across
 * cpu-[un]hotplugs.
 */
static void worker_attach_to_pool(struct worker *worker,
				   struct worker_pool *pool)
{
	mutex_lock(&pool->attach_mutex);

	/*
	 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
	 * online CPUs.  It'll be re-applied when any of the CPUs come up.
	 */
	set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);

	/*
	 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
	 * stable across this function.  See the comments above the
	 * flag definition for details.
	 */
	if (pool->flags & POOL_DISASSOCIATED)
		worker->flags |= WORKER_UNBOUND;

	list_add_tail(&worker->node, &pool->workers);

	mutex_unlock(&pool->attach_mutex);
}

/**
 * worker_detach_from_pool() - detach a worker from its pool
 * @worker: worker which is attached to its pool
 * @pool: the pool @worker is attached to
 *
 * Undo the attaching which had been done in worker_attach_to_pool().  The
 * caller worker shouldn't access to the pool after detached except it has
 * other reference to the pool.
 */
static void worker_detach_from_pool(struct worker *worker,
				    struct worker_pool *pool)
{
	struct completion *detach_completion = NULL;

	mutex_lock(&pool->attach_mutex);
	list_del(&worker->node);
	if (list_empty(&pool->workers))
		detach_completion = pool->detach_completion;
	mutex_unlock(&pool->attach_mutex);

	/* clear leftover flags without pool->lock after it is detached */
	worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);

	if (detach_completion)
		complete(detach_completion);
}

/**
 * create_worker - create a new workqueue worker
 * @pool: pool the new worker will belong to
 *
 * Create and start a new worker which is attached to @pool.
 *
 * CONTEXT:
 * Might sleep.  Does GFP_KERNEL allocations.
 *
 * Return:
 * Pointer to the newly created worker.
 */
static struct worker *create_worker(struct worker_pool *pool)
{
	struct worker *worker = NULL;
	int id = -1;
	char id_buf[16];

	/* ID is needed to determine kthread name */
	id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
	if (id < 0)
		goto fail;

	worker = alloc_worker(pool->node);
	if (!worker)
		goto fail;

	worker->pool = pool;
	worker->id = id;

	if (pool->cpu >= 0)
		snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
			 pool->attrs->nice < 0  ? "H" : "");
	else
		snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);

	worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
					      "kworker/%s", id_buf);
	if (IS_ERR(worker->task))
		goto fail;

	set_user_nice(worker->task, pool->attrs->nice);
	kthread_bind_mask(worker->task, pool->attrs->cpumask);

	/* successful, attach the worker to the pool */
	worker_attach_to_pool(worker, pool);

	/* start the newly created worker */
	spin_lock_irq(&pool->lock);
	worker->pool->nr_workers++;
	worker_enter_idle(worker);
	wake_up_process(worker->task);
	spin_unlock_irq(&pool->lock);

	return worker;

fail:
	if (id >= 0)
		ida_simple_remove(&pool->worker_ida, id);
	kfree(worker);
	return NULL;
}

/**
 * destroy_worker - destroy a workqueue worker
 * @worker: worker to be destroyed
 *
 * Destroy @worker and adjust @pool stats accordingly.  The worker should
 * be idle.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 */
static void destroy_worker(struct worker *worker)
{
	struct worker_pool *pool = worker->pool;

	lockdep_assert_held(&pool->lock);

	/* sanity check frenzy */
	if (WARN_ON(worker->current_work) ||
	    WARN_ON(!list_empty(&worker->scheduled)) ||
	    WARN_ON(!(worker->flags & WORKER_IDLE)))
		return;

	pool->nr_workers--;
	pool->nr_idle--;

	list_del_init(&worker->entry);
	worker->flags |= WORKER_DIE;
	wake_up_process(worker->task);
}

static void idle_worker_timeout(unsigned long __pool)
{
	struct worker_pool *pool = (void *)__pool;

	spin_lock_irq(&pool->lock);

	while (too_many_workers(pool)) {
		struct worker *worker;
		unsigned long expires;

		/* idle_list is kept in LIFO order, check the last one */
		worker = list_entry(pool->idle_list.prev, struct worker, entry);
		expires = worker->last_active + IDLE_WORKER_TIMEOUT;

		if (time_before(jiffies, expires)) {
			mod_timer(&pool->idle_timer, expires);
			break;
		}

		destroy_worker(worker);
	}

	spin_unlock_irq(&pool->lock);
}

static void send_mayday(struct work_struct *work)
{
	struct pool_workqueue *pwq = get_work_pwq(work);
	struct workqueue_struct *wq = pwq->wq;

	lockdep_assert_held(&wq_mayday_lock);

	if (!wq->rescuer)
		return;

	/* mayday mayday mayday */
	if (list_empty(&pwq->mayday_node)) {
		/*
		 * If @pwq is for an unbound wq, its base ref may be put at
		 * any time due to an attribute change.  Pin @pwq until the
		 * rescuer is done with it.
		 */
		get_pwq(pwq);
		list_add_tail(&pwq->mayday_node, &wq->maydays);
		wake_up_process(wq->rescuer->task);
	}
}

static void pool_mayday_timeout(unsigned long __pool)
{
	struct worker_pool *pool = (void *)__pool;
	struct work_struct *work;

	spin_lock_irq(&pool->lock);
	spin_lock(&wq_mayday_lock);		/* for wq->maydays */

	if (need_to_create_worker(pool)) {
		/*
		 * We've been trying to create a new worker but
		 * haven't been successful.  We might be hitting an
		 * allocation deadlock.  Send distress signals to
		 * rescuers.
		 */
		list_for_each_entry(work, &pool->worklist, entry)
			send_mayday(work);
	}

	spin_unlock(&wq_mayday_lock);
	spin_unlock_irq(&pool->lock);

	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
}

/**
 * maybe_create_worker - create a new worker if necessary
 * @pool: pool to create a new worker for
 *
 * Create a new worker for @pool if necessary.  @pool is guaranteed to
 * have at least one idle worker on return from this function.  If
 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
 * sent to all rescuers with works scheduled on @pool to resolve
 * possible allocation deadlock.
 *
 * On return, need_to_create_worker() is guaranteed to be %false and
 * may_start_working() %true.
 *
 * LOCKING:
 * spin_lock_irq(pool->lock) which may be released and regrabbed
 * multiple times.  Does GFP_KERNEL allocations.  Called only from
 * manager.
 */
static void maybe_create_worker(struct worker_pool *pool)
__releases(&pool->lock)
__acquires(&pool->lock)
{
restart:
	spin_unlock_irq(&pool->lock);

	/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);

	while (true) {
		if (create_worker(pool) || !need_to_create_worker(pool))
			break;

		schedule_timeout_interruptible(CREATE_COOLDOWN);

		if (!need_to_create_worker(pool))
			break;
	}

	del_timer_sync(&pool->mayday_timer);
	spin_lock_irq(&pool->lock);
	/*
	 * This is necessary even after a new worker was just successfully
	 * created as @pool->lock was dropped and the new worker might have
	 * already become busy.
	 */
	if (need_to_create_worker(pool))
		goto restart;
}

/**
 * manage_workers - manage worker pool
 * @worker: self
 *
 * Assume the manager role and manage the worker pool @worker belongs
 * to.  At any given time, there can be only zero or one manager per
 * pool.  The exclusion is handled automatically by this function.
 *
 * The caller can safely start processing works on false return.  On
 * true return, it's guaranteed that need_to_create_worker() is false
 * and may_start_working() is true.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock) which may be released and regrabbed
 * multiple times.  Does GFP_KERNEL allocations.
 *
 * Return:
 * %false if the pool doesn't need management and the caller can safely
 * start processing works, %true if management function was performed and
 * the conditions that the caller verified before calling the function may
 * no longer be true.
 */
static bool manage_workers(struct worker *worker)
{
	struct worker_pool *pool = worker->pool;

	/*
	 * Anyone who successfully grabs manager_arb wins the arbitration
	 * and becomes the manager.  mutex_trylock() on pool->manager_arb
	 * failure while holding pool->lock reliably indicates that someone
	 * else is managing the pool and the worker which failed trylock
	 * can proceed to executing work items.  This means that anyone
	 * grabbing manager_arb is responsible for actually performing
	 * manager duties.  If manager_arb is grabbed and released without
	 * actual management, the pool may stall indefinitely.
	 */
	if (!mutex_trylock(&pool->manager_arb))
		return false;
	pool->manager = worker;

	maybe_create_worker(pool);

	pool->manager = NULL;
	mutex_unlock(&pool->manager_arb);
	return true;
}

/**
 * process_one_work - process single work
 * @worker: self
 * @work: work to process
 *
 * Process @work.  This function contains all the logics necessary to
 * process a single work including synchronization against and
 * interaction with other workers on the same cpu, queueing and
 * flushing.  As long as context requirement is met, any worker can
 * call this function to process a work.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock) which is released and regrabbed.
 */
static void process_one_work(struct worker *worker, struct work_struct *work)
__releases(&pool->lock)
__acquires(&pool->lock)
{
	struct pool_workqueue *pwq = get_work_pwq(work);
	struct worker_pool *pool = worker->pool;
	bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
	int work_color;
	struct worker *collision;
#ifdef CONFIG_LOCKDEP
	/*
	 * It is permissible to free the struct work_struct from
	 * inside the function that is called from it, this we need to
	 * take into account for lockdep too.  To avoid bogus "held
	 * lock freed" warnings as well as problems when looking into
	 * work->lockdep_map, make a copy and use that here.
	 */
	struct lockdep_map lockdep_map;

	lockdep_copy_map(&lockdep_map, &work->lockdep_map);
#endif
	/* ensure we're on the correct CPU */
	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
		     raw_smp_processor_id() != pool->cpu);

	/*
	 * A single work shouldn't be executed concurrently by
	 * multiple workers on a single cpu.  Check whether anyone is
	 * already processing the work.  If so, defer the work to the
	 * currently executing one.
	 */
	collision = find_worker_executing_work(pool, work);
	if (unlikely(collision)) {
		move_linked_works(work, &collision->scheduled, NULL);
		return;
	}

	/* claim and dequeue */
	debug_work_deactivate(work);
	hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
	worker->current_work = work;
	worker->current_func = work->func;
	worker->current_pwq = pwq;
	work_color = get_work_color(work);

	list_del_init(&work->entry);

	/*
	 * CPU intensive works don't participate in concurrency management.
	 * They're the scheduler's responsibility.  This takes @worker out
	 * of concurrency management and the next code block will chain
	 * execution of the pending work items.
	 */
	if (unlikely(cpu_intensive))
		worker_set_flags(worker, WORKER_CPU_INTENSIVE);

	/*
	 * Wake up another worker if necessary.  The condition is always
	 * false for normal per-cpu workers since nr_running would always
	 * be >= 1 at this point.  This is used to chain execution of the
	 * pending work items for WORKER_NOT_RUNNING workers such as the
	 * UNBOUND and CPU_INTENSIVE ones.
	 */
	if (need_more_worker(pool))
		wake_up_worker(pool);

	/*
	 * Record the last pool and clear PENDING which should be the last
	 * update to @work.  Also, do this inside @pool->lock so that
	 * PENDING and queued state changes happen together while IRQ is
	 * disabled.
	 */
	set_work_pool_and_clear_pending(work, pool->id);

	spin_unlock_irq(&pool->lock);

	lock_map_acquire_read(&pwq->wq->lockdep_map);
	lock_map_acquire(&lockdep_map);
	trace_workqueue_execute_start(work);
	worker->current_func(work);
	/*
	 * While we must be careful to not use "work" after this, the trace
	 * point will only record its address.
	 */
	trace_workqueue_execute_end(work);
	lock_map_release(&lockdep_map);
	lock_map_release(&pwq->wq->lockdep_map);

	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
		pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
		       "     last function: %pf\n",
		       current->comm, preempt_count(), task_pid_nr(current),
		       worker->current_func);
		debug_show_held_locks(current);
		dump_stack();
	}

	/*
	 * The following prevents a kworker from hogging CPU on !PREEMPT
	 * kernels, where a requeueing work item waiting for something to
	 * happen could deadlock with stop_machine as such work item could
	 * indefinitely requeue itself while all other CPUs are trapped in
	 * stop_machine. At the same time, report a quiescent RCU state so
	 * the same condition doesn't freeze RCU.
	 */
	cond_resched_rcu_qs();

	spin_lock_irq(&pool->lock);

	/* clear cpu intensive status */
	if (unlikely(cpu_intensive))
		worker_clr_flags(worker, WORKER_CPU_INTENSIVE);

	/* we're done with it, release */
	hash_del(&worker->hentry);
	worker->current_work = NULL;
	worker->current_func = NULL;
	worker->current_pwq = NULL;
	worker->desc_valid = false;
	pwq_dec_nr_in_flight(pwq, work_color);
}

/**
 * process_scheduled_works - process scheduled works
 * @worker: self
 *
 * Process all scheduled works.  Please note that the scheduled list
 * may change while processing a work, so this function repeatedly
 * fetches a work from the top and executes it.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock) which may be released and regrabbed
 * multiple times.
 */
static void process_scheduled_works(struct worker *worker)
{
	while (!list_empty(&worker->scheduled)) {
		struct work_struct *work = list_first_entry(&worker->scheduled,
						struct work_struct, entry);
		process_one_work(worker, work);
	}
}

/**
 * worker_thread - the worker thread function
 * @__worker: self
 *
 * The worker thread function.  All workers belong to a worker_pool -
 * either a per-cpu one or dynamic unbound one.  These workers process all
 * work items regardless of their specific target workqueue.  The only
 * exception is work items which belong to workqueues with a rescuer which
 * will be explained in rescuer_thread().
 *
 * Return: 0
 */
static int worker_thread(void *__worker)
{
	struct worker *worker = __worker;
	struct worker_pool *pool = worker->pool;

	/* tell the scheduler that this is a workqueue worker */
	worker->task->flags |= PF_WQ_WORKER;
woke_up:
	spin_lock_irq(&pool->lock);

	/* am I supposed to die? */
	if (unlikely(worker->flags & WORKER_DIE)) {
		spin_unlock_irq(&pool->lock);
		WARN_ON_ONCE(!list_empty(&worker->entry));
		worker->task->flags &= ~PF_WQ_WORKER;

		set_task_comm(worker->task, "kworker/dying");
		ida_simple_remove(&pool->worker_ida, worker->id);
		worker_detach_from_pool(worker, pool);
		kfree(worker);
		return 0;
	}

	worker_leave_idle(worker);
recheck:
	/* no more worker necessary? */
	if (!need_more_worker(pool))
		goto sleep;

	/* do we need to manage? */
	if (unlikely(!may_start_working(pool)) && manage_workers(worker))
		goto recheck;

	/*
	 * ->scheduled list can only be filled while a worker is
	 * preparing to process a work or actually processing it.
	 * Make sure nobody diddled with it while I was sleeping.
	 */
	WARN_ON_ONCE(!list_empty(&worker->scheduled));

	/*
	 * Finish PREP stage.  We're guaranteed to have at least one idle
	 * worker or that someone else has already assumed the manager
	 * role.  This is where @worker starts participating in concurrency
	 * management if applicable and concurrency management is restored
	 * after being rebound.  See rebind_workers() for details.
	 */
	worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);

	do {
		struct work_struct *work =
			list_first_entry(&pool->worklist,
					 struct work_struct, entry);

		pool->watchdog_ts = jiffies;

		if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
			/* optimization path, not strictly necessary */
			process_one_work(worker, work);
			if (unlikely(!list_empty(&worker->scheduled)))
				process_scheduled_works(worker);
		} else {
			move_linked_works(work, &worker->scheduled, NULL);
			process_scheduled_works(worker);
		}
	} while (keep_working(pool));

	worker_set_flags(worker, WORKER_PREP);
sleep:
	/*
	 * pool->lock is held and there's no work to process and no need to
	 * manage, sleep.  Workers are woken up only while holding
	 * pool->lock or from local cpu, so setting the current state
	 * before releasing pool->lock is enough to prevent losing any
	 * event.
	 */
	worker_enter_idle(worker);
	__set_current_state(TASK_INTERRUPTIBLE);
	spin_unlock_irq(&pool->lock);
	schedule();
	goto woke_up;
}

/**
 * rescuer_thread - the rescuer thread function
 * @__rescuer: self
 *
 * Workqueue rescuer thread function.  There's one rescuer for each
 * workqueue which has WQ_MEM_RECLAIM set.
 *
 * Regular work processing on a pool may block trying to create a new
 * worker which uses GFP_KERNEL allocation which has slight chance of
 * developing into deadlock if some works currently on the same queue
 * need to be processed to satisfy the GFP_KERNEL allocation.  This is
 * the problem rescuer solves.
 *
 * When such condition is possible, the pool summons rescuers of all
 * workqueues which have works queued on the pool and let them process
 * those works so that forward progress can be guaranteed.
 *
 * This should happen rarely.
 *
 * Return: 0
 */
static int rescuer_thread(void *__rescuer)
{
	struct worker *rescuer = __rescuer;
	struct workqueue_struct *wq = rescuer->rescue_wq;
	struct list_head *scheduled = &rescuer->scheduled;
	bool should_stop;

	set_user_nice(current, RESCUER_NICE_LEVEL);

	/*
	 * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
	 * doesn't participate in concurrency management.
	 */
	rescuer->task->flags |= PF_WQ_WORKER;
repeat:
	set_current_state(TASK_INTERRUPTIBLE);

	/*
	 * By the time the rescuer is requested to stop, the workqueue
	 * shouldn't have any work pending, but @wq->maydays may still have
	 * pwq(s) queued.  This can happen by non-rescuer workers consuming
	 * all the work items before the rescuer got to them.  Go through
	 * @wq->maydays processing before acting on should_stop so that the
	 * list is always empty on exit.
	 */
	should_stop = kthread_should_stop();

	/* see whether any pwq is asking for help */
	spin_lock_irq(&wq_mayday_lock);

	while (!list_empty(&wq->maydays)) {
		struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
					struct pool_workqueue, mayday_node);
		struct worker_pool *pool = pwq->pool;
		struct work_struct *work, *n;
		bool first = true;

		__set_current_state(TASK_RUNNING);
		list_del_init(&pwq->mayday_node);

		spin_unlock_irq(&wq_mayday_lock);

		worker_attach_to_pool(rescuer, pool);

		spin_lock_irq(&pool->lock);
		rescuer->pool = pool;

		/*
		 * Slurp in all works issued via this workqueue and
		 * process'em.
		 */
		WARN_ON_ONCE(!list_empty(scheduled));
		list_for_each_entry_safe(work, n, &pool->worklist, entry) {
			if (get_work_pwq(work) == pwq) {
				if (first)
					pool->watchdog_ts = jiffies;
				move_linked_works(work, scheduled, &n);
			}
			first = false;
		}

		if (!list_empty(scheduled)) {
			process_scheduled_works(rescuer);

			/*
			 * The above execution of rescued work items could
			 * have created more to rescue through
			 * pwq_activate_first_delayed() or chained
			 * queueing.  Let's put @pwq back on mayday list so
			 * that such back-to-back work items, which may be
			 * being used to relieve memory pressure, don't
			 * incur MAYDAY_INTERVAL delay inbetween.
			 */
			if (need_to_create_worker(pool)) {
				spin_lock(&wq_mayday_lock);
				get_pwq(pwq);
				list_move_tail(&pwq->mayday_node, &wq->maydays);
				spin_unlock(&wq_mayday_lock);
			}
		}

		/*
		 * Put the reference grabbed by send_mayday().  @pool won't
		 * go away while we're still attached to it.
		 */
		put_pwq(pwq);

		/*
		 * Leave this pool.  If need_more_worker() is %true, notify a
		 * regular worker; otherwise, we end up with 0 concurrency
		 * and stalling the execution.
		 */
		if (need_more_worker(pool))
			wake_up_worker(pool);

		rescuer->pool = NULL;
		spin_unlock_irq(&pool->lock);

		worker_detach_from_pool(rescuer, pool);

		spin_lock_irq(&wq_mayday_lock);
	}

	spin_unlock_irq(&wq_mayday_lock);

	if (should_stop) {
		__set_current_state(TASK_RUNNING);
		rescuer->task->flags &= ~PF_WQ_WORKER;
		return 0;
	}

	/* rescuers should never participate in concurrency management */
	WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
	schedule();
	goto repeat;
}

/**
 * check_flush_dependency - check for flush dependency sanity
 * @target_wq: workqueue being flushed
 * @target_work: work item being flushed (NULL for workqueue flushes)
 *
 * %current is trying to flush the whole @target_wq or @target_work on it.
 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
 * reclaiming memory or running on a workqueue which doesn't have
 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
 * a deadlock.
 */
static void check_flush_dependency(struct workqueue_struct *target_wq,
				   struct work_struct *target_work)
{
	work_func_t target_func = target_work ? target_work->func : NULL;
	struct worker *worker;

	if (target_wq->flags & WQ_MEM_RECLAIM)
		return;

	worker = current_wq_worker();

	WARN_ONCE(current->flags & PF_MEMALLOC,
		  "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
		  current->pid, current->comm, target_wq->name, target_func);
	WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
			      (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
		  "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
		  worker->current_pwq->wq->name, worker->current_func,
		  target_wq->name, target_func);
}

struct wq_barrier {
	struct work_struct	work;
	struct completion	done;
	struct task_struct	*task;	/* purely informational */
};

static void wq_barrier_func(struct work_struct *work)
{
	struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
	complete(&barr->done);
}

/**
 * insert_wq_barrier - insert a barrier work
 * @pwq: pwq to insert barrier into
 * @barr: wq_barrier to insert
 * @target: target work to attach @barr to
 * @worker: worker currently executing @target, NULL if @target is not executing
 *
 * @barr is linked to @target such that @barr is completed only after
 * @target finishes execution.  Please note that the ordering
 * guarantee is observed only with respect to @target and on the local
 * cpu.
 *
 * Currently, a queued barrier can't be canceled.  This is because
 * try_to_grab_pending() can't determine whether the work to be
 * grabbed is at the head of the queue and thus can't clear LINKED
 * flag of the previous work while there must be a valid next work
 * after a work with LINKED flag set.
 *
 * Note that when @worker is non-NULL, @target may be modified
 * underneath us, so we can't reliably determine pwq from @target.
 *
 * CONTEXT:
 * spin_lock_irq(pool->lock).
 */
static void insert_wq_barrier(struct pool_workqueue *pwq,
			      struct wq_barrier *barr,
			      struct work_struct *target, struct worker *worker)
{
	struct list_head *head;
	unsigned int linked = 0;

	/*
	 * debugobject calls are safe here even with pool->lock locked
	 * as we know for sure that this will not trigger any of the
	 * checks and call back into the fixup functions where we
	 * might deadlock.
	 */
	INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
	__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
	init_completion(&barr->done);
	barr->task = current;

	/*
	 * If @target is currently being executed, schedule the
	 * barrier to the worker; otherwise, put it after @target.
	 */
	if (worker)
		head = worker->scheduled.next;
	else {
		unsigned long *bits = work_data_bits(target);

		head = target->entry.next;
		/* there can already be other linked works, inherit and set */
		linked = *bits & WORK_STRUCT_LINKED;
		__set_bit(WORK_STRUCT_LINKED_BIT, bits);
	}

	debug_work_activate(&barr->work);
	insert_work(pwq, &barr->work, head,
		    work_color_to_flags(WORK_NO_COLOR) | linked);
}

/**
 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
 * @wq: workqueue being flushed
 * @flush_color: new flush color, < 0 for no-op
 * @work_color: new work color, < 0 for no-op
 *
 * Prepare pwqs for workqueue flushing.
 *
 * If @flush_color is non-negative, flush_color on all pwqs should be
 * -1.  If no pwq has in-flight commands at the specified color, all
 * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
 * has in flight commands, its pwq->flush_color is set to
 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
 * wakeup logic is armed and %true is returned.
 *
 * The caller should have initialized @wq->first_flusher prior to
 * calling this function with non-negative @flush_color.  If
 * @flush_color is negative, no flush color update is done and %false
 * is returned.
 *
 * If @work_color is non-negative, all pwqs should have the same
 * work_color which is previous to @work_color and all will be
 * advanced to @work_color.
 *
 * CONTEXT:
 * mutex_lock(wq->mutex).
 *
 * Return:
 * %true if @flush_color >= 0 and there's something to flush.  %false
 * otherwise.
 */
static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
				      int flush_color, int work_color)
{
	bool wait = false;
	struct pool_workqueue *pwq;

	if (flush_color >= 0) {
		WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
		atomic_set(&wq->nr_pwqs_to_flush, 1);
	}

	for_each_pwq(pwq, wq) {
		struct worker_pool *pool = pwq->pool;

		spin_lock_irq(&pool->lock);

		if (flush_color >= 0) {
			WARN_ON_ONCE(pwq->flush_color != -1);

			if (pwq->nr_in_flight[flush_color]) {
				pwq->flush_color = flush_color;
				atomic_inc(&wq->nr_pwqs_to_flush);
				wait = true;
			}
		}

		if (work_color >= 0) {
			WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
			pwq->work_color = work_color;
		}

		spin_unlock_irq(&pool->lock);
	}

	if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
		complete(&wq->first_flusher->done);

	return wait;
}

/**
 * flush_workqueue - ensure that any scheduled work has run to completion.
 * @wq: workqueue to flush
 *
 * This function sleeps until all work items which were queued on entry
 * have finished execution, but it is not livelocked by new incoming ones.
 */
void flush_workqueue(struct workqueue_struct *wq)
{
	struct wq_flusher this_flusher = {
		.list = LIST_HEAD_INIT(this_flusher.list),
		.flush_color = -1,
		.done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
	};
	int next_color;

	if (WARN_ON(!wq_online))
		return;

	lock_map_acquire(&wq->lockdep_map);
	lock_map_release(&wq->lockdep_map);

	mutex_lock(&wq->mutex);

	/*
	 * Start-to-wait phase
	 */
	next_color = work_next_color(wq->work_color);

	if (next_color != wq->flush_color) {
		/*
		 * Color space is not full.  The current work_color
		 * becomes our flush_color and work_color is advanced
		 * by one.
		 */
		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
		this_flusher.flush_color = wq->work_color;
		wq->work_color = next_color;

		if (!wq->first_flusher) {
			/* no flush in progress, become the first flusher */
			WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);

			wq->first_flusher = &this_flusher;

			if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
						       wq->work_color)) {
				/* nothing to flush, done */
				wq->flush_color = next_color;
				wq->first_flusher = NULL;
				goto out_unlock;
			}
		} else {
			/* wait in queue */
			WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
			list_add_tail(&this_flusher.list, &wq->flusher_queue);
			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
		}
	} else {
		/*
		 * Oops, color space is full, wait on overflow queue.
		 * The next flush completion will assign us
		 * flush_color and transfer to flusher_queue.
		 */
		list_add_tail(&this_flusher.list, &wq->flusher_overflow);
	}

	check_flush_dependency(wq, NULL);

	mutex_unlock(&wq->mutex);

	wait_for_completion(&this_flusher.done);

	/*
	 * Wake-up-and-cascade phase
	 *
	 * First flushers are responsible for cascading flushes and
	 * handling overflow.  Non-first flushers can simply return.
	 */
	if (wq->first_flusher != &this_flusher)
		return;

	mutex_lock(&wq->mutex);

	/* we might have raced, check again with mutex held */
	if (wq->first_flusher != &this_flusher)
		goto out_unlock;

	wq->first_flusher = NULL;

	WARN_ON_ONCE(!list_empty(&this_flusher.list));
	WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);

	while (true) {
		struct wq_flusher *next, *tmp;

		/* complete all the flushers sharing the current flush color */
		list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
			if (next->flush_color != wq->flush_color)
				break;
			list_del_init(&next->list);
			complete(&next->done);
		}

		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
			     wq->flush_color != work_next_color(wq->work_color));

		/* this flush_color is finished, advance by one */
		wq->flush_color = work_next_color(wq->flush_color);

		/* one color has been freed, handle overflow queue */
		if (!list_empty(&wq->flusher_overflow)) {
			/*
			 * Assign the same color to all overflowed
			 * flushers, advance work_color and append to
			 * flusher_queue.  This is the start-to-wait
			 * phase for these overflowed flushers.
			 */
			list_for_each_entry(tmp, &wq->flusher_overflow, list)
				tmp->flush_color = wq->work_color;

			wq->work_color = work_next_color(wq->work_color);

			list_splice_tail_init(&wq->flusher_overflow,
					      &wq->flusher_queue);
			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
		}

		if (list_empty(&wq->flusher_queue)) {
			WARN_ON_ONCE(wq->flush_color != wq->work_color);
			break;
		}

		/*
		 * Need to flush more colors.  Make the next flusher
		 * the new first flusher and arm pwqs.
		 */
		WARN_ON_ONCE(wq->flush_color == wq->work_color);
		WARN_ON_ONCE(wq->flush_color != next->flush_color);

		list_del_init(&next->list);
		wq->first_flusher = next;

		if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
			break;

		/*
		 * Meh... this color is already done, clear first
		 * flusher and repeat cascading.
		 */
		wq->first_flusher = NULL;
	}

out_unlock:
	mutex_unlock(&wq->mutex);
}
EXPORT_SYMBOL(flush_workqueue);

/**
 * drain_workqueue - drain a workqueue
 * @wq: workqueue to drain
 *
 * Wait until the workqueue becomes empty.  While draining is in progress,
 * only chain queueing is allowed.  IOW, only currently pending or running
 * work items on @wq can queue further work items on it.  @wq is flushed
 * repeatedly until it becomes empty.  The number of flushing is determined
 * by the depth of chaining and should be relatively short.  Whine if it
 * takes too long.
 */
void drain_workqueue(struct workqueue_struct *wq)
{
	unsigned int flush_cnt = 0;
	struct pool_workqueue *pwq;

	/*
	 * __queue_work() needs to test whether there are drainers, is much
	 * hotter than drain_workqueue() and already looks at @wq->flags.
	 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
	 */
	mutex_lock(&wq->mutex);
	if (!wq->nr_drainers++)
		wq->flags |= __WQ_DRAINING;
	mutex_unlock(&wq->mutex);
reflush:
	flush_workqueue(wq);

	mutex_lock(&wq->mutex);

	for_each_pwq(pwq, wq) {
		bool drained;

		spin_lock_irq(&pwq->pool->lock);
		drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
		spin_unlock_irq(&pwq->pool->lock);

		if (drained)
			continue;

		if (++flush_cnt == 10 ||
		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
			pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
				wq->name, flush_cnt);

		mutex_unlock(&wq->mutex);
		goto reflush;
	}

	if (!--wq->nr_drainers)
		wq->flags &= ~__WQ_DRAINING;
	mutex_unlock(&wq->mutex);
}
EXPORT_SYMBOL_GPL(drain_workqueue);

static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
{
	struct worker *worker = NULL;
	struct worker_pool *pool;
	struct pool_workqueue *pwq;

	might_sleep();

	local_irq_disable();
	pool = get_work_pool(work);
	if (!pool) {
		local_irq_enable();
		return false;
	}

	spin_lock(&pool->lock);
	/* see the comment in try_to_grab_pending() with the same code */
	pwq = get_work_pwq(work);
	if (pwq) {
		if (unlikely(pwq->pool != pool))
			goto already_gone;
	} else {
		worker = find_worker_executing_work(pool, work);
		if (!worker)
			goto already_gone;
		pwq = worker->current_pwq;
	}

	check_flush_dependency(pwq->wq, work);

	insert_wq_barrier(pwq, barr, work, worker);
	spin_unlock_irq(&pool->lock);

	/*
	 * If @max_active is 1 or rescuer is in use, flushing another work
	 * item on the same workqueue may lead to deadlock.  Make sure the
	 * flusher is not running on the same workqueue by verifying write
	 * access.
	 */
	if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
		lock_map_acquire(&pwq->wq->lockdep_map);
	else
		lock_map_acquire_read(&pwq->wq->lockdep_map);
	lock_map_release(&pwq->wq->lockdep_map);

	return true;
already_gone:
	spin_unlock_irq(&pool->lock);
	return false;
}

/**
 * flush_work - wait for a work to finish executing the last queueing instance
 * @work: the work to flush
 *
 * Wait until @work has finished execution.  @work is guaranteed to be idle
 * on return if it hasn't been requeued since flush started.
 *
 * Return:
 * %true if flush_work() waited for the work to finish execution,
 * %false if it was already idle.
 */
bool flush_work(struct work_struct *work)
{
	struct wq_barrier barr;

	if (WARN_ON(!wq_online))
		return false;

	lock_map_acquire(&work->lockdep_map);
	lock_map_release(&work->lockdep_map);

	if (start_flush_work(work, &barr)) {
		wait_for_completion(&barr.done);
		destroy_work_on_stack(&barr.work);
		return true;
	} else {
		return false;
	}
}
EXPORT_SYMBOL_GPL(flush_work);

struct cwt_wait {
	wait_queue_t		wait;
	struct work_struct	*work;
};

static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
	struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);

	if (cwait->work != key)
		return 0;
	return autoremove_wake_function(wait, mode, sync, key);
}

static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
{
	static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
	unsigned long flags;
	int ret;

	do {
		ret = try_to_grab_pending(work, is_dwork, &flags);
		/*
		 * If someone else is already canceling, wait for it to
		 * finish.  flush_work() doesn't work for PREEMPT_NONE
		 * because we may get scheduled between @work's completion
		 * and the other canceling task resuming and clearing
		 * CANCELING - flush_work() will return false immediately
		 * as @work is no longer busy, try_to_grab_pending() will
		 * return -ENOENT as @work is still being canceled and the
		 * other canceling task won't be able to clear CANCELING as
		 * we're hogging the CPU.
		 *
		 * Let's wait for completion using a waitqueue.  As this
		 * may lead to the thundering herd problem, use a custom
		 * wake function which matches @work along with exclusive
		 * wait and wakeup.
		 */
		if (unlikely(ret == -ENOENT)) {
			struct cwt_wait cwait;

			init_wait(&cwait.wait);
			cwait.wait.func = cwt_wakefn;
			cwait.work = work;

			prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
						  TASK_UNINTERRUPTIBLE);
			if (work_is_canceling(work))
				schedule();
			finish_wait(&cancel_waitq, &cwait.wait);
		}
	} while (unlikely(ret < 0));

	/* tell other tasks trying to grab @work to back off */
	mark_work_canceling(work);
	local_irq_restore(flags);

	/*
	 * This allows canceling during early boot.  We know that @work
	 * isn't executing.
	 */
	if (wq_online)
		flush_work(work);

	clear_work_data(work);

	/*
	 * Paired with prepare_to_wait() above so that either
	 * waitqueue_active() is visible here or !work_is_canceling() is
	 * visible there.
	 */
	smp_mb();
	if (waitqueue_active(&cancel_waitq))
		__wake_up(&cancel_waitq, TASK_NORMAL, 1, work);

	return ret;
}

/**
 * cancel_work_sync - cancel a work and wait for it to finish
 * @work: the work to cancel
 *
 * Cancel @work and wait for its execution to finish.  This function
 * can be used even if the work re-queues itself or migrates to
 * another workqueue.  On return from this function, @work is
 * guaranteed to be not pending or executing on any CPU.
 *
 * cancel_work_sync(&delayed_work->work) must not be used for
 * delayed_work's.  Use cancel_delayed_work_sync() instead.
 *
 * The caller must ensure that the workqueue on which @work was last
 * queued can't be destroyed before this function returns.
 *
 * Return:
 * %true if @work was pending, %false otherwise.
 */
bool cancel_work_sync(struct work_struct *work)
{
	return __cancel_work_timer(work, false);
}
EXPORT_SYMBOL_GPL(cancel_work_sync);

/**
 * flush_delayed_work - wait for a dwork to finish executing the last queueing
 * @dwork: the delayed work to flush
 *
 * Delayed timer is cancelled and the pending work is queued for
 * immediate execution.  Like flush_work(), this function only
 * considers the last queueing instance of @dwork.
 *
 * Return:
 * %true if flush_work() waited for the work to finish execution,
 * %false if it was already idle.
 */
bool flush_delayed_work(struct delayed_work *dwork)
{
	local_irq_disable();
	if (del_timer_sync(&dwork->timer))
		__queue_work(dwork->cpu, dwork->wq, &dwork->work);
	local_irq_enable();
	return flush_work(&dwork->work);
}
EXPORT_SYMBOL(flush_delayed_work);

static bool __cancel_work(struct work_struct *work, bool is_dwork)
{
	unsigned long flags;
	int ret;

	do {
		ret = try_to_grab_pending(work, is_dwork, &flags);
	} while (unlikely(ret == -EAGAIN));

	if (unlikely(ret < 0))
		return false;

	set_work_pool_and_clear_pending(work, get_work_pool_id(work));
	local_irq_restore(flags);
	return ret;
}

/*
 * See cancel_delayed_work()
 */
bool cancel_work(struct work_struct *work)
{
	return __cancel_work(work, false);
}

/**
 * cancel_delayed_work - cancel a delayed work
 * @dwork: delayed_work to cancel
 *
 * Kill off a pending delayed_work.
 *
 * Return: %true if @dwork was pending and canceled; %false if it wasn't
 * pending.
 *
 * Note:
 * The work callback function may still be running on return, unless
 * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
 * use cancel_delayed_work_sync() to wait on it.
 *
 * This function is safe to call from any context including IRQ handler.
 */
bool cancel_delayed_work(struct delayed_work *dwork)
{
	return __cancel_work(&dwork->work, true);
}
EXPORT_SYMBOL(cancel_delayed_work);

/**
 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
 * @dwork: the delayed work cancel
 *
 * This is cancel_work_sync() for delayed works.
 *
 * Return:
 * %true if @dwork was pending, %false otherwise.
 */
bool cancel_delayed_work_sync(struct delayed_work *dwork)
{
	return __cancel_work_timer(&dwork->work, true);
}
EXPORT_SYMBOL(cancel_delayed_work_sync);

/**
 * schedule_on_each_cpu - execute a function synchronously on each online CPU
 * @func: the function to call
 *
 * schedule_on_each_cpu() executes @func on each online CPU using the
 * system workqueue and blocks until all CPUs have completed.
 * schedule_on_each_cpu() is very slow.
 *
 * Return:
 * 0 on success, -errno on failure.
 */
int schedule_on_each_cpu(work_func_t func)
{
	int cpu;
	struct work_struct __percpu *works;

	works = alloc_percpu(struct work_struct);
	if (!works)
		return -ENOMEM;

	get_online_cpus();

	for_each_online_cpu(cpu) {
		struct work_struct *work = per_cpu_ptr(works, cpu);

		INIT_WORK(work, func);
		schedule_work_on(cpu, work);
	}

	for_each_online_cpu(cpu)
		flush_work(per_cpu_ptr(works, cpu));

	put_online_cpus();
	free_percpu(works);
	return 0;
}

/**
 * execute_in_process_context - reliably execute the routine with user context
 * @fn:		the function to execute
 * @ew:		guaranteed storage for the execute work structure (must
 *		be available when the work executes)
 *
 * Executes the function immediately if process context is available,
 * otherwise schedules the function for delayed execution.
 *
 * Return:	0 - function was executed
 *		1 - function was scheduled for execution
 */
int execute_in_process_context(work_func_t fn, struct execute_work *ew)
{
	if (!in_interrupt()) {
		fn(&ew->work);
		return 0;
	}

	INIT_WORK(&ew->work, fn);
	schedule_work(&ew->work);

	return 1;
}
EXPORT_SYMBOL_GPL(execute_in_process_context);

/**
 * free_workqueue_attrs - free a workqueue_attrs
 * @attrs: workqueue_attrs to free
 *
 * Undo alloc_workqueue_attrs().
 */
void free_workqueue_attrs(struct workqueue_attrs *attrs)
{
	if (attrs) {
		free_cpumask_var(attrs->cpumask);
		kfree(attrs);
	}
}

/**
 * alloc_workqueue_attrs - allocate a workqueue_attrs
 * @gfp_mask: allocation mask to use
 *
 * Allocate a new workqueue_attrs, initialize with default settings and
 * return it.
 *
 * Return: The allocated new workqueue_attr on success. %NULL on failure.
 */
struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
{
	struct workqueue_attrs *attrs;

	attrs = kzalloc(sizeof(*attrs), gfp_mask);
	if (!attrs)
		goto fail;
	if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
		goto fail;

	cpumask_copy(attrs->cpumask, cpu_possible_mask);
	return attrs;
fail:
	free_workqueue_attrs(attrs);
	return NULL;
}

static void copy_workqueue_attrs(struct workqueue_attrs *to,
				 const struct workqueue_attrs *from)
{
	to->nice = from->nice;
	cpumask_copy(to->cpumask, from->cpumask);
	/*
	 * Unlike hash and equality test, this function doesn't ignore
	 * ->no_numa as it is used for both pool and wq attrs.  Instead,
	 * get_unbound_pool() explicitly clears ->no_numa after copying.
	 */
	to->no_numa = from->no_numa;
}

/* hash value of the content of @attr */
static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
{
	u32 hash = 0;

	hash = jhash_1word(attrs->nice, hash);
	hash = jhash(cpumask_bits(attrs->cpumask),
		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
	return hash;
}

/* content equality test */
static bool wqattrs_equal(const struct workqueue_attrs *a,
			  const struct workqueue_attrs *b)
{
	if (a->nice != b->nice)
		return false;
	if (!cpumask_equal(a->cpumask, b->cpumask))
		return false;
	return true;
}

/**
 * init_worker_pool - initialize a newly zalloc'd worker_pool
 * @pool: worker_pool to initialize
 *
 * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
 *
 * Return: 0 on success, -errno on failure.  Even on failure, all fields
 * inside @pool proper are initialized and put_unbound_pool() can be called
 * on @pool safely to release it.
 */
static int init_worker_pool(struct worker_pool *pool)
{
	spin_lock_init(&pool->lock);
	pool->id = -1;
	pool->cpu = -1;
	pool->node = NUMA_NO_NODE;
	pool->flags |= POOL_DISASSOCIATED;
	pool->watchdog_ts = jiffies;
	INIT_LIST_HEAD(&pool->worklist);
	INIT_LIST_HEAD(&pool->idle_list);
	hash_init(pool->busy_hash);

	init_timer_deferrable(&pool->idle_timer);
	pool->idle_timer.function = idle_worker_timeout;
	pool->idle_timer.data = (unsigned long)pool;

	setup_timer(&pool->mayday_timer, pool_mayday_timeout,
		    (unsigned long)pool);

	mutex_init(&pool->manager_arb);
	mutex_init(&pool->attach_mutex);
	INIT_LIST_HEAD(&pool->workers);

	ida_init(&pool->worker_ida);
	INIT_HLIST_NODE(&pool->hash_node);
	pool->refcnt = 1;

	/* shouldn't fail above this point */
	pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
	if (!pool->attrs)
		return -ENOMEM;
	return 0;
}

static void rcu_free_wq(struct rcu_head *rcu)
{
	struct workqueue_struct *wq =
		container_of(rcu, struct workqueue_struct, rcu);

	if (!(wq->flags & WQ_UNBOUND))
		free_percpu(wq->cpu_pwqs);
	else
		free_workqueue_attrs(wq->unbound_attrs);

	kfree(wq->rescuer);
	kfree(wq);
}

static void rcu_free_pool(struct rcu_head *rcu)
{
	struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);

	ida_destroy(&pool->worker_ida);
	free_workqueue_attrs(pool->attrs);
	kfree(pool);
}

/**
 * put_unbound_pool - put a worker_pool
 * @pool: worker_pool to put
 *
 * Put @pool.  If its refcnt reaches zero, it gets destroyed in sched-RCU
 * safe manner.  get_unbound_pool() calls this function on its failure path
 * and this function should be able to release pools which went through,
 * successfully or not, init_worker_pool().
 *
 * Should be called with wq_pool_mutex held.
 */
static void put_unbound_pool(struct worker_pool *pool)
{
	DECLARE_COMPLETION_ONSTACK(detach_completion);
	struct worker *worker;

	lockdep_assert_held(&wq_pool_mutex);

	if (--pool->refcnt)
		return;

	/* sanity checks */
	if (WARN_ON(!(pool->cpu < 0)) ||
	    WARN_ON(!list_empty(&pool->worklist)))
		return;

	/* release id and unhash */
	if (pool->id >= 0)
		idr_remove(&worker_pool_idr, pool->id);
	hash_del(&pool->hash_node);

	/*
	 * Become the manager and destroy all workers.  Grabbing
	 * manager_arb prevents @pool's workers from blocking on
	 * attach_mutex.
	 */
	mutex_lock(&pool->manager_arb);

	spin_lock_irq(&pool->lock);
	while ((worker = first_idle_worker(pool)))
		destroy_worker(worker);
	WARN_ON(pool->nr_workers || pool->nr_idle);
	spin_unlock_irq(&pool->lock);

	mutex_lock(&pool->attach_mutex);
	if (!list_empty(&pool->workers))
		pool->detach_completion = &detach_completion;
	mutex_unlock(&pool->attach_mutex);

	if (pool->detach_completion)
		wait_for_completion(pool->detach_completion);

	mutex_unlock(&pool->manager_arb);

	/* shut down the timers */
	del_timer_sync(&pool->idle_timer);
	del_timer_sync(&pool->mayday_timer);

	/* sched-RCU protected to allow dereferences from get_work_pool() */
	call_rcu_sched(&pool->rcu, rcu_free_pool);
}

/**
 * get_unbound_pool - get a worker_pool with the specified attributes
 * @attrs: the attributes of the worker_pool to get
 *
 * Obtain a worker_pool which has the same attributes as @attrs, bump the
 * reference count and return it.  If there already is a matching
 * worker_pool, it will be used; otherwise, this function attempts to
 * create a new one.
 *
 * Should be called with wq_pool_mutex held.
 *
 * Return: On success, a worker_pool with the same attributes as @attrs.
 * On failure, %NULL.
 */
static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
{
	u32 hash = wqattrs_hash(attrs);
	struct worker_pool *pool;
	int node;
	int target_node = NUMA_NO_NODE;

	lockdep_assert_held(&wq_pool_mutex);

	/* do we already have a matching pool? */
	hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
		if (wqattrs_equal(pool->attrs, attrs)) {
			pool->refcnt++;
			return pool;
		}
	}

	/* if cpumask is contained inside a NUMA node, we belong to that node */
	if (wq_numa_enabled) {
		for_each_node(node) {
			if (cpumask_subset(attrs->cpumask,
					   wq_numa_possible_cpumask[node])) {
				target_node = node;
				break;
			}
		}
	}

	/* nope, create a new one */
	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
	if (!pool || init_worker_pool(pool) < 0)
		goto fail;

	lockdep_set_subclass(&pool->lock, 1);	/* see put_pwq() */
	copy_workqueue_attrs(pool->attrs, attrs);
	pool->node = target_node;

	/*
	 * no_numa isn't a worker_pool attribute, always clear it.  See
	 * 'struct workqueue_attrs' comments for detail.
	 */
	pool->attrs->no_numa = false;

	if (worker_pool_assign_id(pool) < 0)
		goto fail;

	/* create and start the initial worker */
	if (wq_online && !create_worker(pool))
		goto fail;

	/* install */
	hash_add(unbound_pool_hash, &pool->hash_node, hash);

	return pool;
fail:
	if (pool)
		put_unbound_pool(pool);
	return NULL;
}

static void rcu_free_pwq(struct rcu_head *rcu)
{
	kmem_cache_free(pwq_cache,
			container_of(rcu, struct pool_workqueue, rcu));
}

/*
 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
 * and needs to be destroyed.
 */
static void pwq_unbound_release_workfn(struct work_struct *work)
{
	struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
						  unbound_release_work);
	struct workqueue_struct *wq = pwq->wq;
	struct worker_pool *pool = pwq->pool;
	bool is_last;

	if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
		return;

	mutex_lock(&wq->mutex);
	list_del_rcu(&pwq->pwqs_node);
	is_last = list_empty(&wq->pwqs);
	mutex_unlock(&wq->mutex);

	mutex_lock(&wq_pool_mutex);
	put_unbound_pool(pool);
	mutex_unlock(&wq_pool_mutex);

	call_rcu_sched(&pwq->rcu, rcu_free_pwq);

	/*
	 * If we're the last pwq going away, @wq is already dead and no one
	 * is gonna access it anymore.  Schedule RCU free.
	 */
	if (is_last)
		call_rcu_sched(&wq->rcu, rcu_free_wq);
}

/**
 * pwq_adjust_max_active - update a pwq's max_active to the current setting
 * @pwq: target pool_workqueue
 *
 * If @pwq isn't freezing, set @pwq->max_active to the associated
 * workqueue's saved_max_active and activate delayed work items
 * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
 */
static void pwq_adjust_max_active(struct pool_workqueue *pwq)
{
	struct workqueue_struct *wq = pwq->wq;
	bool freezable = wq->flags & WQ_FREEZABLE;
	unsigned long flags;

	/* for @wq->saved_max_active */
	lockdep_assert_held(&wq->mutex);

	/* fast exit for non-freezable wqs */
	if (!freezable && pwq->max_active == wq->saved_max_active)
		return;

	/* this function can be called during early boot w/ irq disabled */
	spin_lock_irqsave(&pwq->pool->lock, flags);

	/*
	 * During [un]freezing, the caller is responsible for ensuring that
	 * this function is called at least once after @workqueue_freezing
	 * is updated and visible.
	 */
	if (!freezable || !workqueue_freezing) {
		pwq->max_active = wq->saved_max_active;

		while (!list_empty(&pwq->delayed_works) &&
		       pwq->nr_active < pwq->max_active)
			pwq_activate_first_delayed(pwq);

		/*
		 * Need to kick a worker after thawed or an unbound wq's
		 * max_active is bumped.  It's a slow path.  Do it always.
		 */
		wake_up_worker(pwq->pool);
	} else {
		pwq->max_active = 0;
	}

	spin_unlock_irqrestore(&pwq->pool->lock, flags);
}

/* initialize newly alloced @pwq which is associated with @wq and @pool */
static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
		     struct worker_pool *pool)
{
	BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);

	memset(pwq, 0, sizeof(*pwq));

	pwq->pool = pool;
	pwq->wq = wq;
	pwq->flush_color = -1;
	pwq->refcnt = 1;
	INIT_LIST_HEAD(&pwq->delayed_works);
	INIT_LIST_HEAD(&pwq->pwqs_node);
	INIT_LIST_HEAD(&pwq->mayday_node);
	INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
}

/* sync @pwq with the current state of its associated wq and link it */
static void link_pwq(struct pool_workqueue *pwq)
{
	struct workqueue_struct *wq = pwq->wq;

	lockdep_assert_held(&wq->mutex);

	/* may be called multiple times, ignore if already linked */
	if (!list_empty(&pwq->pwqs_node))
		return;

	/* set the matching work_color */
	pwq->work_color = wq->work_color;

	/* sync max_active to the current setting */
	pwq_adjust_max_active(pwq);

	/* link in @pwq */
	list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
}

/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
					const struct workqueue_attrs *attrs)
{
	struct worker_pool *pool;
	struct pool_workqueue *pwq;

	lockdep_assert_held(&wq_pool_mutex);

	pool = get_unbound_pool(attrs);
	if (!pool)
		return NULL;

	pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
	if (!pwq) {
		put_unbound_pool(pool);
		return NULL;
	}

	init_pwq(pwq, wq, pool);
	return pwq;
}

/**
 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
 * @attrs: the wq_attrs of the default pwq of the target workqueue
 * @node: the target NUMA node
 * @cpu_going_down: if >= 0, the CPU to consider as offline
 * @cpumask: outarg, the resulting cpumask
 *
 * Calculate the cpumask a workqueue with @attrs should use on @node.  If
 * @cpu_going_down is >= 0, that cpu is considered offline during
 * calculation.  The result is stored in @cpumask.
 *
 * If NUMA affinity is not enabled, @attrs->cpumask is always used.  If
 * enabled and @node has online CPUs requested by @attrs, the returned
 * cpumask is the intersection of the possible CPUs of @node and
 * @attrs->cpumask.
 *
 * The caller is responsible for ensuring that the cpumask of @node stays
 * stable.
 *
 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
 * %false if equal.
 */
static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
				 int cpu_going_down, cpumask_t *cpumask)
{
	if (!wq_numa_enabled || attrs->no_numa)
		goto use_dfl;

	/* does @node have any online CPUs @attrs wants? */
	cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
	if (cpu_going_down >= 0)
		cpumask_clear_cpu(cpu_going_down, cpumask);

	if (cpumask_empty(cpumask))
		goto use_dfl;

	/* yeap, return possible CPUs in @node that @attrs wants */
	cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
	return !cpumask_equal(cpumask, attrs->cpumask);

use_dfl:
	cpumask_copy(cpumask, attrs->cpumask);
	return false;
}

/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
						   int node,
						   struct pool_workqueue *pwq)
{
	struct pool_workqueue *old_pwq;

	lockdep_assert_held(&wq_pool_mutex);
	lockdep_assert_held(&wq->mutex);

	/* link_pwq() can handle duplicate calls */
	link_pwq(pwq);

	old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
	rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
	return old_pwq;
}

/* context to store the prepared attrs & pwqs before applying */
struct apply_wqattrs_ctx {
	struct workqueue_struct	*wq;		/* target workqueue */
	struct workqueue_attrs	*attrs;		/* attrs to apply */
	struct list_head	list;		/* queued for batching commit */
	struct pool_workqueue	*dfl_pwq;
	struct pool_workqueue	*pwq_tbl[];
};

/* free the resources after success or abort */
static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
{
	if (ctx) {
		int node;

		for_each_node(node)
			put_pwq_unlocked(ctx->pwq_tbl[node]);
		put_pwq_unlocked(ctx->dfl_pwq);

		free_workqueue_attrs(ctx->attrs);

		kfree(ctx);
	}
}

/* allocate the attrs and pwqs for later installation */
static struct apply_wqattrs_ctx *
apply_wqattrs_prepare(struct workqueue_struct *wq,
		      const struct workqueue_attrs *attrs)
{
	struct apply_wqattrs_ctx *ctx;
	struct workqueue_attrs *new_attrs, *tmp_attrs;
	int node;

	lockdep_assert_held(&wq_pool_mutex);

	ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
		      GFP_KERNEL);

	new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
	tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
	if (!ctx || !new_attrs || !tmp_attrs)
		goto out_free;

	/*
	 * Calculate the attrs of the default pwq.
	 * If the user configured cpumask doesn't overlap with the
	 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
	 */
	copy_workqueue_attrs(new_attrs, attrs);
	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
	if (unlikely(cpumask_empty(new_attrs->cpumask)))
		cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);

	/*
	 * We may create multiple pwqs with differing cpumasks.  Make a
	 * copy of @new_attrs which will be modified and used to obtain
	 * pools.
	 */
	copy_workqueue_attrs(tmp_attrs, new_attrs);

	/*
	 * If something goes wrong during CPU up/down, we'll fall back to
	 * the default pwq covering whole @attrs->cpumask.  Always create
	 * it even if we don't use it immediately.
	 */
	ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
	if (!ctx->dfl_pwq)
		goto out_free;

	for_each_node(node) {
		if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
			ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
			if (!ctx->pwq_tbl[node])
				goto out_free;
		} else {
			ctx->dfl_pwq->refcnt++;
			ctx->pwq_tbl[node] = ctx->dfl_pwq;
		}
	}

	/* save the user configured attrs and sanitize it. */
	copy_workqueue_attrs(new_attrs, attrs);
	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
	ctx->attrs = new_attrs;

	ctx->wq = wq;
	free_workqueue_attrs(tmp_attrs);
	return ctx;

out_free:
	free_workqueue_attrs(tmp_attrs);
	free_workqueue_attrs(new_attrs);
	apply_wqattrs_cleanup(ctx);
	return NULL;
}

/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
{
	int node;

	/* all pwqs have been created successfully, let's install'em */
	mutex_lock(&ctx->wq->mutex);

	copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);

	/* save the previous pwq and install the new one */
	for_each_node(node)
		ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
							  ctx->pwq_tbl[node]);

	/* @dfl_pwq might not have been used, ensure it's linked */
	link_pwq(ctx->dfl_pwq);
	swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);

	mutex_unlock(&ctx->wq->mutex);
}

static void apply_wqattrs_lock(void)
{
	/* CPUs should stay stable across pwq creations and installations */
	get_online_cpus();
	mutex_lock(&wq_pool_mutex);
}

static void apply_wqattrs_unlock(void)
{
	mutex_unlock(&wq_pool_mutex);
	put_online_cpus();
}

static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
					const struct workqueue_attrs *attrs)
{
	struct apply_wqattrs_ctx *ctx;

	/* only unbound workqueues can change attributes */
	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
		return -EINVAL;

	/* creating multiple pwqs breaks ordering guarantee */
	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
		return -EINVAL;

	ctx = apply_wqattrs_prepare(wq, attrs);
	if (!ctx)
		return -ENOMEM;

	/* the ctx has been prepared successfully, let's commit it */
	apply_wqattrs_commit(ctx);
	apply_wqattrs_cleanup(ctx);

	return 0;
}

/**
 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
 * @wq: the target workqueue
 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
 *
 * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
 * machines, this function maps a separate pwq to each NUMA node with
 * possibles CPUs in @attrs->cpumask so that work items are affine to the
 * NUMA node it was issued on.  Older pwqs are released as in-flight work
 * items finish.  Note that a work item which repeatedly requeues itself
 * back-to-back will stay on its current pwq.
 *
 * Performs GFP_KERNEL allocations.
 *
 * Return: 0 on success and -errno on failure.
 */
int apply_workqueue_attrs(struct workqueue_struct *wq,
			  const struct workqueue_attrs *attrs)
{
	int ret;

	apply_wqattrs_lock();
	ret = apply_workqueue_attrs_locked(wq, attrs);
	apply_wqattrs_unlock();

	return ret;
}

/**
 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
 * @wq: the target workqueue
 * @cpu: the CPU coming up or going down
 * @online: whether @cpu is coming up or going down
 *
 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
 * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update NUMA affinity of
 * @wq accordingly.
 *
 * If NUMA affinity can't be adjusted due to memory allocation failure, it
 * falls back to @wq->dfl_pwq which may not be optimal but is always
 * correct.
 *
 * Note that when the last allowed CPU of a NUMA node goes offline for a
 * workqueue with a cpumask spanning multiple nodes, the workers which were
 * already executing the work items for the workqueue will lose their CPU
 * affinity and may execute on any CPU.  This is similar to how per-cpu
 * workqueues behave on CPU_DOWN.  If a workqueue user wants strict
 * affinity, it's the user's responsibility to flush the work item from
 * CPU_DOWN_PREPARE.
 */
static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
				   bool online)
{
	int node = cpu_to_node(cpu);
	int cpu_off = online ? -1 : cpu;
	struct pool_workqueue *old_pwq = NULL, *pwq;
	struct workqueue_attrs *target_attrs;
	cpumask_t *cpumask;

	lockdep_assert_held(&wq_pool_mutex);

	if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
	    wq->unbound_attrs->no_numa)
		return;

	/*
	 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
	 * Let's use a preallocated one.  The following buf is protected by
	 * CPU hotplug exclusion.
	 */
	target_attrs = wq_update_unbound_numa_attrs_buf;
	cpumask = target_attrs->cpumask;

	copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
	pwq = unbound_pwq_by_node(wq, node);

	/*
	 * Let's determine what needs to be done.  If the target cpumask is
	 * different from the default pwq's, we need to compare it to @pwq's
	 * and create a new one if they don't match.  If the target cpumask
	 * equals the default pwq's, the default pwq should be used.
	 */
	if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
		if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
			return;
	} else {
		goto use_dfl_pwq;
	}

	/* create a new pwq */
	pwq = alloc_unbound_pwq(wq, target_attrs);
	if (!pwq) {
		pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
			wq->name);
		goto use_dfl_pwq;
	}

	/* Install the new pwq. */
	mutex_lock(&wq->mutex);
	old_pwq = numa_pwq_tbl_install(wq, node, pwq);
	goto out_unlock;

use_dfl_pwq:
	mutex_lock(&wq->mutex);
	spin_lock_irq(&wq->dfl_pwq->pool->lock);
	get_pwq(wq->dfl_pwq);
	spin_unlock_irq(&wq->dfl_pwq->pool->lock);
	old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
out_unlock:
	mutex_unlock(&wq->mutex);
	put_pwq_unlocked(old_pwq);
}

static int alloc_and_link_pwqs(struct workqueue_struct *wq)
{
	bool highpri = wq->flags & WQ_HIGHPRI;
	int cpu, ret;

	if (!(wq->flags & WQ_UNBOUND)) {
		wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
		if (!wq->cpu_pwqs)
			return -ENOMEM;

		for_each_possible_cpu(cpu) {
			struct pool_workqueue *pwq =
				per_cpu_ptr(wq->cpu_pwqs, cpu);
			struct worker_pool *cpu_pools =
				per_cpu(cpu_worker_pools, cpu);

			init_pwq(pwq, wq, &cpu_pools[highpri]);

			mutex_lock(&wq->mutex);
			link_pwq(pwq);
			mutex_unlock(&wq->mutex);
		}
		return 0;
	} else if (wq->flags & __WQ_ORDERED) {
		ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
		/* there should only be single pwq for ordering guarantee */
		WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
			      wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
		     "ordering guarantee broken for workqueue %s\n", wq->name);
		return ret;
	} else {
		return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
	}
}

static int wq_clamp_max_active(int max_active, unsigned int flags,
			       const char *name)
{
	int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;

	if (max_active < 1 || max_active > lim)
		pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
			max_active, name, 1, lim);

	return clamp_val(max_active, 1, lim);
}

struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
					       unsigned int flags,
					       int max_active,
					       struct lock_class_key *key,
					       const char *lock_name, ...)
{
	size_t tbl_size = 0;
	va_list args;
	struct workqueue_struct *wq;
	struct pool_workqueue *pwq;

	/* see the comment above the definition of WQ_POWER_EFFICIENT */
	if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
		flags |= WQ_UNBOUND;

	/* allocate wq and format name */
	if (flags & WQ_UNBOUND)
		tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);

	wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
	if (!wq)
		return NULL;

	if (flags & WQ_UNBOUND) {
		wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
		if (!wq->unbound_attrs)
			goto err_free_wq;
	}

	va_start(args, lock_name);
	vsnprintf(wq->name, sizeof(wq->name), fmt, args);
	va_end(args);

	max_active = max_active ?: WQ_DFL_ACTIVE;
	max_active = wq_clamp_max_active(max_active, flags, wq->name);

	/* init wq */
	wq->flags = flags;
	wq->saved_max_active = max_active;
	mutex_init(&wq->mutex);
	atomic_set(&wq->nr_pwqs_to_flush, 0);
	INIT_LIST_HEAD(&wq->pwqs);
	INIT_LIST_HEAD(&wq->flusher_queue);
	INIT_LIST_HEAD(&wq->flusher_overflow);
	INIT_LIST_HEAD(&wq->maydays);

	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
	INIT_LIST_HEAD(&wq->list);

	if (alloc_and_link_pwqs(wq) < 0)
		goto err_free_wq;

	/*
	 * Workqueues which may be used during memory reclaim should
	 * have a rescuer to guarantee forward progress.
	 */
	if (flags & WQ_MEM_RECLAIM) {
		struct worker *rescuer;

		rescuer = alloc_worker(NUMA_NO_NODE);
		if (!rescuer)
			goto err_destroy;

		rescuer->rescue_wq = wq;
		rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
					       wq->name);
		if (IS_ERR(rescuer->task)) {
			kfree(rescuer);
			goto err_destroy;
		}

		wq->rescuer = rescuer;
		kthread_bind_mask(rescuer->task, cpu_possible_mask);
		wake_up_process(rescuer->task);
	}

	if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
		goto err_destroy;

	/*
	 * wq_pool_mutex protects global freeze state and workqueues list.
	 * Grab it, adjust max_active and add the new @wq to workqueues
	 * list.
	 */
	mutex_lock(&wq_pool_mutex);

	mutex_lock(&wq->mutex);
	for_each_pwq(pwq, wq)
		pwq_adjust_max_active(pwq);
	mutex_unlock(&wq->mutex);

	list_add_tail_rcu(&wq->list, &workqueues);

	mutex_unlock(&wq_pool_mutex);

	return wq;

err_free_wq:
	free_workqueue_attrs(wq->unbound_attrs);
	kfree(wq);
	return NULL;
err_destroy:
	destroy_workqueue(wq);
	return NULL;
}
EXPORT_SYMBOL_GPL(__alloc_workqueue_key);

/**
 * destroy_workqueue - safely terminate a workqueue
 * @wq: target workqueue
 *
 * Safely destroy a workqueue. All work currently pending will be done first.
 */
void destroy_workqueue(struct workqueue_struct *wq)
{
	struct pool_workqueue *pwq;
	int node;

	/* drain it before proceeding with destruction */
	drain_workqueue(wq);

	/* sanity checks */
	mutex_lock(&wq->mutex);
	for_each_pwq(pwq, wq) {
		int i;

		for (i = 0; i < WORK_NR_COLORS; i++) {
			if (WARN_ON(pwq->nr_in_flight[i])) {
				mutex_unlock(&wq->mutex);
				show_workqueue_state();
				return;
			}
		}

		if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
		    WARN_ON(pwq->nr_active) ||
		    WARN_ON(!list_empty(&pwq->delayed_works))) {
			mutex_unlock(&wq->mutex);
			show_workqueue_state();
			return;
		}
	}
	mutex_unlock(&wq->mutex);

	/*
	 * wq list is used to freeze wq, remove from list after
	 * flushing is complete in case freeze races us.
	 */
	mutex_lock(&wq_pool_mutex);
	list_del_rcu(&wq->list);
	mutex_unlock(&wq_pool_mutex);

	workqueue_sysfs_unregister(wq);

	if (wq->rescuer)
		kthread_stop(wq->rescuer->task);

	if (!(wq->flags & WQ_UNBOUND)) {
		/*
		 * The base ref is never dropped on per-cpu pwqs.  Directly
		 * schedule RCU free.
		 */
		call_rcu_sched(&wq->rcu, rcu_free_wq);
	} else {
		/*
		 * We're the sole accessor of @wq at this point.  Directly
		 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
		 * @wq will be freed when the last pwq is released.
		 */
		for_each_node(node) {
			pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
			RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
			put_pwq_unlocked(pwq);
		}

		/*
		 * Put dfl_pwq.  @wq may be freed any time after dfl_pwq is
		 * put.  Don't access it afterwards.
		 */
		pwq = wq->dfl_pwq;
		wq->dfl_pwq = NULL;
		put_pwq_unlocked(pwq);
	}
}
EXPORT_SYMBOL_GPL(destroy_workqueue);

/**
 * workqueue_set_max_active - adjust max_active of a workqueue
 * @wq: target workqueue
 * @max_active: new max_active value.
 *
 * Set max_active of @wq to @max_active.
 *
 * CONTEXT:
 * Don't call from IRQ context.
 */
void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
{
	struct pool_workqueue *pwq;

	/* disallow meddling with max_active for ordered workqueues */
	if (WARN_ON(wq->flags & __WQ_ORDERED))
		return;

	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);

	mutex_lock(&wq->mutex);

	wq->saved_max_active = max_active;

	for_each_pwq(pwq, wq)
		pwq_adjust_max_active(pwq);

	mutex_unlock(&wq->mutex);
}
EXPORT_SYMBOL_GPL(workqueue_set_max_active);

/**
 * current_is_workqueue_rescuer - is %current workqueue rescuer?
 *
 * Determine whether %current is a workqueue rescuer.  Can be used from
 * work functions to determine whether it's being run off the rescuer task.
 *
 * Return: %true if %current is a workqueue rescuer. %false otherwise.
 */
bool current_is_workqueue_rescuer(void)
{
	struct worker *worker = current_wq_worker();

	return worker && worker->rescue_wq;
}

/**
 * workqueue_congested - test whether a workqueue is congested
 * @cpu: CPU in question
 * @wq: target workqueue
 *
 * Test whether @wq's cpu workqueue for @cpu is congested.  There is
 * no synchronization around this function and the test result is
 * unreliable and only useful as advisory hints or for debugging.
 *
 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
 * Note that both per-cpu and unbound workqueues may be associated with
 * multiple pool_workqueues which have separate congested states.  A
 * workqueue being congested on one CPU doesn't mean the workqueue is also
 * contested on other CPUs / NUMA nodes.
 *
 * Return:
 * %true if congested, %false otherwise.
 */
bool workqueue_congested(int cpu, struct workqueue_struct *wq)
{
	struct pool_workqueue *pwq;
	bool ret;

	rcu_read_lock_sched();

	if (cpu == WORK_CPU_UNBOUND)
		cpu = smp_processor_id();

	if (!(wq->flags & WQ_UNBOUND))
		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
	else
		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));

	ret = !list_empty(&pwq->delayed_works);
	rcu_read_unlock_sched();

	return ret;
}
EXPORT_SYMBOL_GPL(workqueue_congested);

/**
 * work_busy - test whether a work is currently pending or running
 * @work: the work to be tested
 *
 * Test whether @work is currently pending or running.  There is no
 * synchronization around this function and the test result is
 * unreliable and only useful as advisory hints or for debugging.
 *
 * Return:
 * OR'd bitmask of WORK_BUSY_* bits.
 */
unsigned int work_busy(struct work_struct *work)
{
	struct worker_pool *pool;
	unsigned long flags;
	unsigned int ret = 0;

	if (work_pending(work))
		ret |= WORK_BUSY_PENDING;

	local_irq_save(flags);
	pool = get_work_pool(work);
	if (pool) {
		spin_lock(&pool->lock);
		if (find_worker_executing_work(pool, work))
			ret |= WORK_BUSY_RUNNING;
		spin_unlock(&pool->lock);
	}
	local_irq_restore(flags);

	return ret;
}
EXPORT_SYMBOL_GPL(work_busy);

/**
 * set_worker_desc - set description for the current work item
 * @fmt: printf-style format string
 * @...: arguments for the format string
 *
 * This function can be called by a running work function to describe what
 * the work item is about.  If the worker task gets dumped, this
 * information will be printed out together to help debugging.  The
 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
 */
void set_worker_desc(const char *fmt, ...)
{
	struct worker *worker = current_wq_worker();
	va_list args;

	if (worker) {
		va_start(args, fmt);
		vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
		va_end(args);
		worker->desc_valid = true;
	}
}

/**
 * print_worker_info - print out worker information and description
 * @log_lvl: the log level to use when printing
 * @task: target task
 *
 * If @task is a worker and currently executing a work item, print out the
 * name of the workqueue being serviced and worker description set with
 * set_worker_desc() by the currently executing work item.
 *
 * This function can be safely called on any task as long as the
 * task_struct itself is accessible.  While safe, this function isn't
 * synchronized and may print out mixups or garbages of limited length.
 */
void print_worker_info(const char *log_lvl, struct task_struct *task)
{
	work_func_t *fn = NULL;
	char name[WQ_NAME_LEN] = { };
	char desc[WORKER_DESC_LEN] = { };
	struct pool_workqueue *pwq = NULL;
	struct workqueue_struct *wq = NULL;
	bool desc_valid = false;
	struct worker *worker;

	if (!(task->flags & PF_WQ_WORKER))
		return;

	/*
	 * This function is called without any synchronization and @task
	 * could be in any state.  Be careful with dereferences.
	 */
	worker = kthread_probe_data(task);

	/*
	 * Carefully copy the associated workqueue's workfn and name.  Keep
	 * the original last '\0' in case the original contains garbage.
	 */
	probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
	probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
	probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
	probe_kernel_read(name, wq->name, sizeof(name) - 1);

	/* copy worker description */
	probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
	if (desc_valid)
		probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);

	if (fn || name[0] || desc[0]) {
		printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
		if (desc[0])
			pr_cont(" (%s)", desc);
		pr_cont("\n");
	}
}

static void pr_cont_pool_info(struct worker_pool *pool)
{
	pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
	if (pool->node != NUMA_NO_NODE)
		pr_cont(" node=%d", pool->node);
	pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
}

static void pr_cont_work(bool comma, struct work_struct *work)
{
	if (work->func == wq_barrier_func) {
		struct wq_barrier *barr;

		barr = container_of(work, struct wq_barrier, work);

		pr_cont("%s BAR(%d)", comma ? "," : "",
			task_pid_nr(barr->task));
	} else {
		pr_cont("%s %pf", comma ? "," : "", work->func);
	}
}

static void show_pwq(struct pool_workqueue *pwq)
{
	struct worker_pool *pool = pwq->pool;
	struct work_struct *work;
	struct worker *worker;
	bool has_in_flight = false, has_pending = false;
	int bkt;

	pr_info("  pwq %d:", pool->id);
	pr_cont_pool_info(pool);

	pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
		!list_empty(&pwq->mayday_node) ? " MAYDAY" : "");

	hash_for_each(pool->busy_hash, bkt, worker, hentry) {
		if (worker->current_pwq == pwq) {
			has_in_flight = true;
			break;
		}
	}
	if (has_in_flight) {
		bool comma = false;

		pr_info("    in-flight:");
		hash_for_each(pool->busy_hash, bkt, worker, hentry) {
			if (worker->current_pwq != pwq)
				continue;

			pr_cont("%s %d%s:%pf", comma ? "," : "",
				task_pid_nr(worker->task),
				worker == pwq->wq->rescuer ? "(RESCUER)" : "",
				worker->current_func);
			list_for_each_entry(work, &worker->scheduled, entry)
				pr_cont_work(false, work);
			comma = true;
		}
		pr_cont("\n");
	}

	list_for_each_entry(work, &pool->worklist, entry) {
		if (get_work_pwq(work) == pwq) {
			has_pending = true;
			break;
		}
	}
	if (has_pending) {
		bool comma = false;

		pr_info("    pending:");
		list_for_each_entry(work, &pool->worklist, entry) {
			if (get_work_pwq(work) != pwq)
				continue;

			pr_cont_work(comma, work);
			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
		}
		pr_cont("\n");
	}

	if (!list_empty(&pwq->delayed_works)) {
		bool comma = false;

		pr_info("    delayed:");
		list_for_each_entry(work, &pwq->delayed_works, entry) {
			pr_cont_work(comma, work);
			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
		}
		pr_cont("\n");
	}
}

/**
 * show_workqueue_state - dump workqueue state
 *
 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
 * all busy workqueues and pools.
 */
void show_workqueue_state(void)
{
	struct workqueue_struct *wq;
	struct worker_pool *pool;
	unsigned long flags;
	int pi;

	rcu_read_lock_sched();

	pr_info("Showing busy workqueues and worker pools:\n");

	list_for_each_entry_rcu(wq, &workqueues, list) {
		struct pool_workqueue *pwq;
		bool idle = true;

		for_each_pwq(pwq, wq) {
			if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
				idle = false;
				break;
			}
		}
		if (idle)
			continue;

		pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);

		for_each_pwq(pwq, wq) {
			spin_lock_irqsave(&pwq->pool->lock, flags);
			if (pwq->nr_active || !list_empty(&pwq->delayed_works))
				show_pwq(pwq);
			spin_unlock_irqrestore(&pwq->pool->lock, flags);
		}
	}

	for_each_pool(pool, pi) {
		struct worker *worker;
		bool first = true;

		spin_lock_irqsave(&pool->lock, flags);
		if (pool->nr_workers == pool->nr_idle)
			goto next_pool;

		pr_info("pool %d:", pool->id);
		pr_cont_pool_info(pool);
		pr_cont(" hung=%us workers=%d",
			jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
			pool->nr_workers);
		if (pool->manager)
			pr_cont(" manager: %d",
				task_pid_nr(pool->manager->task));
		list_for_each_entry(worker, &pool->idle_list, entry) {
			pr_cont(" %s%d",