Home Home > GIT Browse
summaryrefslogtreecommitdiff
blob: d551d5f53f0932bd252dac0b297a7b1c7c4d9698 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
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
/*
 * 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 is one worker pool for each CPU and
 * one extra for works which are better served by workers which are
 * not bound to any specific CPU.
 *
 * 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 "workqueue_sched.h"

enum {
	/* global_cwq flags */
	GCWQ_MANAGE_WORKERS	= 1 << 0,	/* need to manage workers */
	GCWQ_MANAGING_WORKERS	= 1 << 1,	/* managing workers */
	GCWQ_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */
	GCWQ_FREEZING		= 1 << 3,	/* freeze in progress */
	GCWQ_HIGHPRI_PENDING	= 1 << 4,	/* highpri works on queue */

	/* worker flags */
	WORKER_STARTED		= 1 << 0,	/* started */
	WORKER_DIE		= 1 << 1,	/* die die die */
	WORKER_IDLE		= 1 << 2,	/* is idle */
	WORKER_PREP		= 1 << 3,	/* preparing to run works */
	WORKER_ROGUE		= 1 << 4,	/* not bound to any cpu */
	WORKER_REBIND		= 1 << 5,	/* mom is home, come back */
	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */

	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
				  WORKER_CPU_INTENSIVE | WORKER_UNBOUND,

	/* gcwq->trustee_state */
	TRUSTEE_START		= 0,		/* start */
	TRUSTEE_IN_CHARGE	= 1,		/* trustee in charge of gcwq */
	TRUSTEE_BUTCHER		= 2,		/* butcher workers */
	TRUSTEE_RELEASE		= 3,		/* release workers */
	TRUSTEE_DONE		= 4,		/* trustee is done */

	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
	BUSY_WORKER_HASH_SIZE	= 1 << BUSY_WORKER_HASH_ORDER,
	BUSY_WORKER_HASH_MASK	= BUSY_WORKER_HASH_SIZE - 1,

	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 */
	TRUSTEE_COOLDOWN	= HZ / 10,	/* for trustee draining */

	/*
	 * Rescue workers are used only on emergencies and shared by
	 * all cpus.  Give -20.
	 */
	RESCUER_NICE_LEVEL	= -20,
};

/*
 * 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: gcwq->lock protected.  Access with gcwq->lock held.
 *
 * X: During normal operation, modification requires gcwq->lock and
 *    should be done only from local cpu.  Either disabling preemption
 *    on local cpu or grabbing gcwq->lock is enough for read access.
 *    If GCWQ_DISASSOCIATED is set, it's identical to L.
 *
 * F: wq->flush_mutex protected.
 *
 * W: workqueue_lock protected.
 */

struct global_cwq;

/*
 * The poor guys doing the actual heavy lifting.  All on-duty workers
 * are either serving the manager role, on idle list or on busy hash.
 */
struct worker {
	/* on idle list while idle, on busy hash table while busy */
	union {
		struct list_head	entry;	/* L: while idle */
		struct hlist_node	hentry;	/* L: while busy */
	};

	struct work_struct	*current_work;	/* L: work being processed */
	struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
	struct list_head	scheduled;	/* L: scheduled works */
	struct task_struct	*task;		/* I: worker task */
	struct global_cwq	*gcwq;		/* I: the associated gcwq */
	/* 64 bytes boundary on 64bit, 32 on 32bit */
	unsigned long		last_active;	/* L: last active timestamp */
	unsigned int		flags;		/* X: flags */
	int			id;		/* I: worker id */
	struct work_struct	rebind_work;	/* L: rebind worker to cpu */
};

/*
 * Global per-cpu workqueue.  There's one and only one for each cpu
 * and all works are queued and processed here regardless of their
 * target workqueues.
 */
struct global_cwq {
	spinlock_t		lock;		/* the gcwq lock */
	struct list_head	worklist;	/* L: list of pending works */
	unsigned int		cpu;		/* I: the associated cpu */
	unsigned int		flags;		/* L: GCWQ_* flags */

	int			nr_workers;	/* L: total number of workers */
	int			nr_idle;	/* L: currently idle ones */

	/* workers are chained either in the idle_list or busy_hash */
	struct list_head	idle_list;	/* X: list of idle workers */
	struct hlist_head	busy_hash[BUSY_WORKER_HASH_SIZE];
						/* L: hash of busy workers */

	struct timer_list	idle_timer;	/* L: worker idle timeout */
	struct timer_list	mayday_timer;	/* L: SOS timer for dworkers */

	struct ida		worker_ida;	/* L: for worker IDs */

	struct task_struct	*trustee;	/* L: for gcwq shutdown */
	unsigned int		trustee_state;	/* L: trustee state */
	wait_queue_head_t	trustee_wait;	/* trustee wait */
	struct worker		*first_idle;	/* L: first idle worker */
} ____cacheline_aligned_in_smp;

/*
 * The per-CPU workqueue.  The lower WORK_STRUCT_FLAG_BITS of
 * work_struct->data are used for flags and thus cwqs need to be
 * aligned at two's power of the number of flag bits.
 */
struct cpu_workqueue_struct {
	struct global_cwq	*gcwq;		/* I: the associated gcwq */
	struct workqueue_struct *wq;		/* I: the owning workqueue */
	int			work_color;	/* L: current color */
	int			flush_color;	/* L: flushing color */
	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 */
};

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

/*
 * All cpumasks are assumed to be always set on UP and thus can't be
 * used to determine whether there's something to be done.
 */
#ifdef CONFIG_SMP
typedef cpumask_var_t mayday_mask_t;
#define mayday_test_and_set_cpu(cpu, mask)	\
	cpumask_test_and_set_cpu((cpu), (mask))
#define mayday_clear_cpu(cpu, mask)		cpumask_clear_cpu((cpu), (mask))
#define for_each_mayday_cpu(cpu, mask)		for_each_cpu((cpu), (mask))
#define alloc_mayday_mask(maskp, gfp)		zalloc_cpumask_var((maskp), (gfp))
#define free_mayday_mask(mask)			free_cpumask_var((mask))
#else
typedef unsigned long mayday_mask_t;
#define mayday_test_and_set_cpu(cpu, mask)	test_and_set_bit(0, &(mask))
#define mayday_clear_cpu(cpu, mask)		clear_bit(0, &(mask))
#define for_each_mayday_cpu(cpu, mask)		if ((cpu) = 0, (mask))
#define alloc_mayday_mask(maskp, gfp)		true
#define free_mayday_mask(mask)			do { } while (0)
#endif

/*
 * The externally visible workqueue abstraction is an array of
 * per-CPU workqueues:
 */
struct workqueue_struct {
	unsigned int		flags;		/* W: WQ_* flags */
	union {
		struct cpu_workqueue_struct __percpu	*pcpu;
		struct cpu_workqueue_struct		*single;
		unsigned long				v;
	} cpu_wq;				/* I: cwq's */
	struct list_head	list;		/* W: list of all workqueues */

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

	mayday_mask_t		mayday_mask;	/* cpus requesting rescue */
	struct worker		*rescuer;	/* I: rescue worker */

	int			nr_drainers;	/* W: drain in progress */
	int			saved_max_active; /* W: saved cwq max_active */
	const char		*name;		/* I: workqueue name */
#ifdef CONFIG_LOCKDEP
	struct lockdep_map	lockdep_map;
#endif
};

struct workqueue_struct *system_wq __read_mostly;
struct workqueue_struct *system_long_wq __read_mostly;
struct workqueue_struct *system_nrt_wq __read_mostly;
struct workqueue_struct *system_unbound_wq __read_mostly;
struct workqueue_struct *system_freezable_wq __read_mostly;
struct workqueue_struct *system_nrt_freezable_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_wq);
EXPORT_SYMBOL_GPL(system_long_wq);
EXPORT_SYMBOL_GPL(system_nrt_wq);
EXPORT_SYMBOL_GPL(system_unbound_wq);
EXPORT_SYMBOL_GPL(system_freezable_wq);
EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);

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

#define for_each_busy_worker(worker, i, pos, gcwq)			\
	for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)			\
		hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)

static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
				  unsigned int sw)
{
	if (cpu < nr_cpu_ids) {
		if (sw & 1) {
			cpu = cpumask_next(cpu, mask);
			if (cpu < nr_cpu_ids)
				return cpu;
		}
		if (sw & 2)
			return WORK_CPU_UNBOUND;
	}
	return WORK_CPU_NONE;
}

static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
				struct workqueue_struct *wq)
{
	return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
}

/*
 * CPU iterators
 *
 * An extra gcwq is defined for an invalid cpu number
 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
 * specific CPU.  The following iterators are similar to
 * for_each_*_cpu() iterators but also considers the unbound gcwq.
 *
 * for_each_gcwq_cpu()		: possible CPUs + WORK_CPU_UNBOUND
 * for_each_online_gcwq_cpu()	: online CPUs + WORK_CPU_UNBOUND
 * for_each_cwq_cpu()		: possible CPUs for bound workqueues,
 *				  WORK_CPU_UNBOUND for unbound workqueues
 */
#define for_each_gcwq_cpu(cpu)						\
	for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3);		\
	     (cpu) < WORK_CPU_NONE;					\
	     (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))

#define for_each_online_gcwq_cpu(cpu)					\
	for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3);		\
	     (cpu) < WORK_CPU_NONE;					\
	     (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))

#define for_each_cwq_cpu(cpu, wq)					\
	for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq));	\
	     (cpu) < WORK_CPU_NONE;					\
	     (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))

#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;
}

/*
 * fixup_init is called when:
 * - an active object is initialized
 */
static int 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 1;
	default:
		return 0;
	}
}

/*
 * fixup_activate is called when:
 * - an active object is activated
 * - an unknown object is activated (might be a statically initialized object)
 */
static int work_fixup_activate(void *addr, enum debug_obj_state state)
{
	struct work_struct *work = addr;

	switch (state) {

	case ODEBUG_STATE_NOTAVAILABLE:
		/*
		 * This is not really a fixup. The work struct was
		 * statically initialized. We just make sure that it
		 * is tracked in the object tracker.
		 */
		if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
			debug_object_init(work, &work_debug_descr);
			debug_object_activate(work, &work_debug_descr);
			return 0;
		}
		WARN_ON_ONCE(1);
		return 0;

	case ODEBUG_STATE_ACTIVE:
		WARN_ON(1);

	default:
		return 0;
	}
}

/*
 * fixup_free is called when:
 * - an active object is freed
 */
static int 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 1;
	default:
		return 0;
	}
}

static struct debug_obj_descr work_debug_descr = {
	.name		= "work_struct",
	.debug_hint	= work_debug_hint,
	.fixup_init	= work_fixup_init,
	.fixup_activate	= work_fixup_activate,
	.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);

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

/* Serializes the accesses to the list of workqueues. */
static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues);
static bool workqueue_freezing;		/* W: have wqs started freezing? */

/*
 * The almighty global cpu workqueues.  nr_running is the only field
 * which is expected to be used frequently by other cpus via
 * try_to_wake_up().  Put it in a separate cacheline.
 */
static DEFINE_PER_CPU(struct global_cwq, global_cwq);
static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);

/*
 * Global cpu workqueue and nr_running counter for unbound gcwq.  The
 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
 * workers have WORKER_UNBOUND set.
 */
static struct global_cwq unbound_global_cwq;
static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0);	/* always 0 */

static int worker_thread(void *__worker);

static struct global_cwq *get_gcwq(unsigned int cpu)
{
	if (cpu != WORK_CPU_UNBOUND)
		return &per_cpu(global_cwq, cpu);
	else
		return &unbound_global_cwq;
}

static atomic_t *get_gcwq_nr_running(unsigned int cpu)
{
	if (cpu != WORK_CPU_UNBOUND)
		return &per_cpu(gcwq_nr_running, cpu);
	else
		return &unbound_gcwq_nr_running;
}

static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
					    struct workqueue_struct *wq)
{
	if (!(wq->flags & WQ_UNBOUND)) {
		if (likely(cpu < nr_cpu_ids)) {
#ifdef CONFIG_SMP
			return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
#else
			return wq->cpu_wq.single;
#endif
		}
	} else if (likely(cpu == WORK_CPU_UNBOUND))
		return wq->cpu_wq.single;
	return NULL;
}

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;
}

/*
 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
 * work is on queue.  Once execution starts, WORK_STRUCT_CWQ is
 * cleared and the work data contains the cpu number it was last on.
 *
 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
 * cwq, cpu or clear work->data.  These functions should only be
 * called while the work is owned - ie. while the PENDING bit is set.
 *
 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
 * corresponding to a work.  gcwq is available once the work has been
 * queued anywhere after initialization.  cwq is available only from
 * queueing until execution starts.
 */
static inline void set_work_data(struct work_struct *work, unsigned long data,
				 unsigned long flags)
{
	BUG_ON(!work_pending(work));
	atomic_long_set(&work->data, data | flags | work_static(work));
}

static void set_work_cwq(struct work_struct *work,
			 struct cpu_workqueue_struct *cwq,
			 unsigned long extra_flags)
{
	set_work_data(work, (unsigned long)cwq,
		      WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
}

static void set_work_cpu(struct work_struct *work, unsigned int cpu)
{
	set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
}

static void clear_work_data(struct work_struct *work)
{
	set_work_data(work, WORK_STRUCT_NO_CPU, 0);
}

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

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

static struct global_cwq *get_work_gcwq(struct work_struct *work)
{
	unsigned long data = atomic_long_read(&work->data);
	unsigned int cpu;

	if (data & WORK_STRUCT_CWQ)
		return ((struct cpu_workqueue_struct *)
			(data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;

	cpu = data >> WORK_STRUCT_FLAG_BITS;
	if (cpu == WORK_CPU_NONE)
		return NULL;

	BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
	return get_gcwq(cpu);
}

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

static bool __need_more_worker(struct global_cwq *gcwq)
{
	return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
		gcwq->flags & GCWQ_HIGHPRI_PENDING;
}

/*
 * Need to wake up a worker?  Called from anything but currently
 * running workers.
 */
static bool need_more_worker(struct global_cwq *gcwq)
{
	return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
}

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

/* Do I need to keep working?  Called from currently running workers. */
static bool keep_working(struct global_cwq *gcwq)
{
	atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);

	return !list_empty(&gcwq->worklist) &&
		(atomic_read(nr_running) <= 1 ||
		 gcwq->flags & GCWQ_HIGHPRI_PENDING);
}

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

/* Do I need to be the manager? */
static bool need_to_manage_workers(struct global_cwq *gcwq)
{
	return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
}

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

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

/*
 * Wake up functions.
 */

/* Return the first worker.  Safe with preemption disabled */
static struct worker *first_worker(struct global_cwq *gcwq)
{
	if (unlikely(list_empty(&gcwq->idle_list)))
		return NULL;

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

/**
 * wake_up_worker - wake up an idle worker
 * @gcwq: gcwq to wake worker for
 *
 * Wake up the first idle worker of @gcwq.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 */
static void wake_up_worker(struct global_cwq *gcwq)
{
	struct worker *worker = first_worker(gcwq);

	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, unsigned int cpu)
{
	struct worker *worker = kthread_data(task);

	if (!(worker->flags & WORKER_NOT_RUNNING))
		atomic_inc(get_gcwq_nr_running(cpu));
}

/**
 * wq_worker_sleeping - a worker is going to sleep
 * @task: task going to sleep
 * @cpu: CPU in question, must be the current CPU number
 *
 * 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)
 *
 * RETURNS:
 * Worker task on @cpu to wake up, %NULL if none.
 */
struct task_struct *wq_worker_sleeping(struct task_struct *task,
				       unsigned int cpu)
{
	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
	struct global_cwq *gcwq = get_gcwq(cpu);
	atomic_t *nr_running = get_gcwq_nr_running(cpu);

	if (worker->flags & WORKER_NOT_RUNNING)
		return NULL;

	/* this can only happen on the local cpu */
	BUG_ON(cpu != raw_smp_processor_id());

	/*
	 * 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 trustee is not in
	 * charge and we're 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 gcwq lock is safe.
	 */
	if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
		to_wakeup = first_worker(gcwq);
	return to_wakeup ? to_wakeup->task : NULL;
}

/**
 * worker_set_flags - set worker flags and adjust nr_running accordingly
 * @worker: self
 * @flags: flags to set
 * @wakeup: wakeup an idle worker if necessary
 *
 * Set @flags in @worker->flags and adjust nr_running accordingly.  If
 * nr_running becomes zero and @wakeup is %true, an idle worker is
 * woken up.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock)
 */
static inline void worker_set_flags(struct worker *worker, unsigned int flags,
				    bool wakeup)
{
	struct global_cwq *gcwq = worker->gcwq;

	WARN_ON_ONCE(worker->task != current);

	/*
	 * If transitioning into NOT_RUNNING, adjust nr_running and
	 * wake up an idle worker as necessary if requested by
	 * @wakeup.
	 */
	if ((flags & WORKER_NOT_RUNNING) &&
	    !(worker->flags & WORKER_NOT_RUNNING)) {
		atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);

		if (wakeup) {
			if (atomic_dec_and_test(nr_running) &&
			    !list_empty(&gcwq->worklist))
				wake_up_worker(gcwq);
		} else
			atomic_dec(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(gcwq->lock)
 */
static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
{
	struct global_cwq *gcwq = worker->gcwq;
	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(get_gcwq_nr_running(gcwq->cpu));
}

/**
 * busy_worker_head - return the busy hash head for a work
 * @gcwq: gcwq of interest
 * @work: work to be hashed
 *
 * Return hash head of @gcwq for @work.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 *
 * RETURNS:
 * Pointer to the hash head.
 */
static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
					   struct work_struct *work)
{
	const int base_shift = ilog2(sizeof(struct work_struct));
	unsigned long v = (unsigned long)work;

	/* simple shift and fold hash, do we need something better? */
	v >>= base_shift;
	v += v >> BUSY_WORKER_HASH_ORDER;
	v &= BUSY_WORKER_HASH_MASK;

	return &gcwq->busy_hash[v];
}

/**
 * __find_worker_executing_work - find worker which is executing a work
 * @gcwq: gcwq of interest
 * @bwh: hash head as returned by busy_worker_head()
 * @work: work to find worker for
 *
 * Find a worker which is executing @work on @gcwq.  @bwh should be
 * the hash head obtained by calling busy_worker_head() with the same
 * work.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 *
 * RETURNS:
 * Pointer to worker which is executing @work if found, NULL
 * otherwise.
 */
static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
						   struct hlist_head *bwh,
						   struct work_struct *work)
{
	struct worker *worker;
	struct hlist_node *tmp;

	hlist_for_each_entry(worker, tmp, bwh, hentry)
		if (worker->current_work == work)
			return worker;
	return NULL;
}

/**
 * find_worker_executing_work - find worker which is executing a work
 * @gcwq: gcwq of interest
 * @work: work to find worker for
 *
 * Find a worker which is executing @work on @gcwq.  This function is
 * identical to __find_worker_executing_work() except that this
 * function calculates @bwh itself.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 *
 * RETURNS:
 * Pointer to worker which is executing @work if found, NULL
 * otherwise.
 */
static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
						 struct work_struct *work)
{
	return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
					    work);
}

/**
 * gcwq_determine_ins_pos - find insertion position
 * @gcwq: gcwq of interest
 * @cwq: cwq a work is being queued for
 *
 * A work for @cwq is about to be queued on @gcwq, determine insertion
 * position for the work.  If @cwq is for HIGHPRI wq, the work is
 * queued at the head of the queue but in FIFO order with respect to
 * other HIGHPRI works; otherwise, at the end of the queue.  This
 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
 * there are HIGHPRI works pending.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 *
 * RETURNS:
 * Pointer to inserstion position.
 */
static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
					       struct cpu_workqueue_struct *cwq)
{
	struct work_struct *twork;

	if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
		return &gcwq->worklist;

	list_for_each_entry(twork, &gcwq->worklist, entry) {
		struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);

		if (!(tcwq->wq->flags & WQ_HIGHPRI))
			break;
	}

	gcwq->flags |= GCWQ_HIGHPRI_PENDING;
	return &twork->entry;
}

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

	/* we own @work, set data and link */
	set_work_cwq(work, cwq, extra_flags);

	/*
	 * Ensure that we get the right work->data if we see the
	 * result of list_add() below, see try_to_grab_pending().
	 */
	smp_wmb();

	list_add_tail(&work->entry, head);

	/*
	 * Ensure either worker_sched_deactivated() 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(gcwq))
		wake_up_worker(gcwq);
}

/*
 * Test whether @work is being queued from another work executing on the
 * same workqueue.  This is rather expensive and should only be used from
 * cold paths.
 */
static bool is_chained_work(struct workqueue_struct *wq)
{
	unsigned long flags;
	unsigned int cpu;

	for_each_gcwq_cpu(cpu) {
		struct global_cwq *gcwq = get_gcwq(cpu);
		struct worker *worker;
		struct hlist_node *pos;
		int i;

		spin_lock_irqsave(&gcwq->lock, flags);
		for_each_busy_worker(worker, i, pos, gcwq) {
			if (worker->task != current)
				continue;
			spin_unlock_irqrestore(&gcwq->lock, flags);
			/*
			 * I'm @worker, no locking necessary.  See if @work
			 * is headed to the same workqueue.
			 */
			return worker->current_cwq->wq == wq;
		}
		spin_unlock_irqrestore(&gcwq->lock, flags);
	}
	return false;
}

static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
			 struct work_struct *work)
{
	struct global_cwq *gcwq;
	struct cpu_workqueue_struct *cwq;
	struct list_head *worklist;
	unsigned int work_flags;
	unsigned long flags;

	debug_work_activate(work);

	/* if dying, only works from the same workqueue are allowed */
	if (unlikely(wq->flags & WQ_DRAINING) &&
	    WARN_ON_ONCE(!is_chained_work(wq)))
		return;

	/* determine gcwq to use */
	if (!(wq->flags & WQ_UNBOUND)) {
		struct global_cwq *last_gcwq;

		if (unlikely(cpu == WORK_CPU_UNBOUND))
			cpu = raw_smp_processor_id();

		/*
		 * It's multi cpu.  If @wq is non-reentrant and @work
		 * was previously on a different cpu, it might still
		 * be running there, in which case the work needs to
		 * be queued on that cpu to guarantee non-reentrance.
		 */
		gcwq = get_gcwq(cpu);
		if (wq->flags & WQ_NON_REENTRANT &&
		    (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
			struct worker *worker;

			spin_lock_irqsave(&last_gcwq->lock, flags);

			worker = find_worker_executing_work(last_gcwq, work);

			if (worker && worker->current_cwq->wq == wq)
				gcwq = last_gcwq;
			else {
				/* meh... not running there, queue here */
				spin_unlock_irqrestore(&last_gcwq->lock, flags);
				spin_lock_irqsave(&gcwq->lock, flags);
			}
		} else
			spin_lock_irqsave(&gcwq->lock, flags);
	} else {
		gcwq = get_gcwq(WORK_CPU_UNBOUND);
		spin_lock_irqsave(&gcwq->lock, flags);
	}

	/* gcwq determined, get cwq and queue */
	cwq = get_cwq(gcwq->cpu, wq);
	trace_workqueue_queue_work(cpu, cwq, work);

	BUG_ON(!list_empty(&work->entry));

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

	if (likely(cwq->nr_active < cwq->max_active)) {
		trace_workqueue_activate_work(work);
		cwq->nr_active++;
		worklist = gcwq_determine_ins_pos(gcwq, cwq);
	} else {
		work_flags |= WORK_STRUCT_DELAYED;
		worklist = &cwq->delayed_works;
	}

	insert_work(cwq, work, worklist, work_flags);

	spin_unlock_irqrestore(&gcwq->lock, flags);
}

/**
 * queue_work - queue work on a workqueue
 * @wq: workqueue to use
 * @work: work to queue
 *
 * Returns 0 if @work was already on a queue, non-zero otherwise.
 *
 * We queue the work to the CPU on which it was submitted, but if the CPU dies
 * it can be processed by another CPU.
 */
int queue_work(struct workqueue_struct *wq, struct work_struct *work)
{
	int ret;

	ret = queue_work_on(get_cpu(), wq, work);
	put_cpu();

	return ret;
}
EXPORT_SYMBOL_GPL(queue_work);

/**
 * queue_work_on - queue work on specific cpu
 * @cpu: CPU number to execute work on
 * @wq: workqueue to use
 * @work: work to queue
 *
 * Returns 0 if @work was already on a queue, non-zero otherwise.
 *
 * We queue the work to a specific CPU, the caller must ensure it
 * can't go away.
 */
int
queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
{
	int ret = 0;

	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
		__queue_work(cpu, wq, work);
		ret = 1;
	}
	return ret;
}
EXPORT_SYMBOL_GPL(queue_work_on);

static void delayed_work_timer_fn(unsigned long __data)
{
	struct delayed_work *dwork = (struct delayed_work *)__data;
	struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);

	__queue_work(smp_processor_id(), cwq->wq, &dwork->work);
}

/**
 * queue_delayed_work - queue work on a workqueue after delay
 * @wq: workqueue to use
 * @dwork: delayable work to queue
 * @delay: number of jiffies to wait before queueing
 *
 * Returns 0 if @work was already on a queue, non-zero otherwise.
 */
int queue_delayed_work(struct workqueue_struct *wq,
			struct delayed_work *dwork, unsigned long delay)
{
	if (delay == 0)
		return queue_work(wq, &dwork->work);

	return queue_delayed_work_on(-1, wq, dwork, delay);
}
EXPORT_SYMBOL_GPL(queue_delayed_work);

/**
 * 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
 *
 * Returns 0 if @work was already on a queue, non-zero otherwise.
 */
int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
			struct delayed_work *dwork, unsigned long delay)
{
	int ret = 0;
	struct timer_list *timer = &dwork->timer;
	struct work_struct *work = &dwork->work;

	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
		unsigned int lcpu;

		BUG_ON(timer_pending(timer));
		BUG_ON(!list_empty(&work->entry));

		timer_stats_timer_set_start_info(&dwork->timer);

		/*
		 * This stores cwq for the moment, for the timer_fn.
		 * Note that the work's gcwq is preserved to allow
		 * reentrance detection for delayed works.
		 */
		if (!(wq->flags & WQ_UNBOUND)) {
			struct global_cwq *gcwq = get_work_gcwq(work);

			if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
				lcpu = gcwq->cpu;
			else
				lcpu = raw_smp_processor_id();
		} else
			lcpu = WORK_CPU_UNBOUND;

		set_work_cwq(work, get_cwq(lcpu, wq), 0);

		timer->expires = jiffies + delay;
		timer->data = (unsigned long)dwork;
		timer->function = delayed_work_timer_fn;

		if (unlikely(cpu >= 0))
			add_timer_on(timer, cpu);
		else
			add_timer(timer);
		ret = 1;
	}
	return ret;
}
EXPORT_SYMBOL_GPL(queue_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(gcwq->lock).
 */
static void worker_enter_idle(struct worker *worker)
{
	struct global_cwq *gcwq = worker->gcwq;

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

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

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

	if (likely(!(worker->flags & WORKER_ROGUE))) {
		if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
			mod_timer(&gcwq->idle_timer,
				  jiffies + IDLE_WORKER_TIMEOUT);
	} else
		wake_up_all(&gcwq->trustee_wait);

	/*
	 * Sanity check nr_running.  Because trustee releases gcwq->lock
	 * between setting %WORKER_ROGUE and zapping nr_running, the
	 * warning may trigger spuriously.  Check iff trustee is idle.
	 */
	WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE &&
		     gcwq->nr_workers == gcwq->nr_idle &&
		     atomic_read(get_gcwq_nr_running(gcwq->cpu)));
}

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

	BUG_ON(!(worker->flags & WORKER_IDLE));
	worker_clr_flags(worker, WORKER_IDLE);
	gcwq->nr_idle--;
	list_del_init(&worker->entry);
}

/**
 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
 * @worker: self
 *
 * Works which are scheduled while the cpu is online must at least be
 * scheduled to a worker which is bound to the cpu so that if they are
 * flushed from cpu callbacks while cpu is going down, they are
 * guaranteed to execute on the cpu.
 *
 * This function is to be used by rogue workers and rescuers to bind
 * themselves to the target cpu and may race with cpu going down or
 * coming online.  kthread_bind() can't be used because it may put the
 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
 * verbatim as it's best effort and blocking and gcwq may be
 * [dis]associated in the meantime.
 *
 * This function tries set_cpus_allowed() and locks gcwq and verifies
 * the binding against GCWQ_DISASSOCIATED which is set during
 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
 * idle state or fetches works without dropping lock, it can guarantee
 * the scheduling requirement described in the first paragraph.
 *
 * CONTEXT:
 * Might sleep.  Called without any lock but returns with gcwq->lock
 * held.
 *
 * RETURNS:
 * %true if the associated gcwq is online (@worker is successfully
 * bound), %false if offline.
 */
static bool worker_maybe_bind_and_lock(struct worker *worker)
__acquires(&gcwq->lock)
{
	struct global_cwq *gcwq = worker->gcwq;
	struct task_struct *task = worker->task;

	while (true) {
		/*
		 * The following call may fail, succeed or succeed
		 * without actually migrating the task to the cpu if
		 * it races with cpu hotunplug operation.  Verify
		 * against GCWQ_DISASSOCIATED.
		 */
		if (!(gcwq->flags & GCWQ_DISASSOCIATED))
			set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));

		spin_lock_irq(&gcwq->lock);
		if (gcwq->flags & GCWQ_DISASSOCIATED)
			return false;
		if (task_cpu(task) == gcwq->cpu &&
		    cpumask_equal(&current->cpus_allowed,
				  get_cpu_mask(gcwq->cpu)))
			return true;
		spin_unlock_irq(&gcwq->lock);

		/*
		 * We've raced with CPU hot[un]plug.  Give it a breather
		 * and retry migration.  cond_resched() is required here;
		 * otherwise, we might deadlock against cpu_stop trying to
		 * bring down the CPU on non-preemptive kernel.
		 */
		cpu_relax();
		cond_resched();
	}
}

/*
 * Function for worker->rebind_work used to rebind rogue busy workers
 * to the associated cpu which is coming back online.  This is
 * scheduled by cpu up but can race with other cpu hotplug operations
 * and may be executed twice without intervening cpu down.
 */
static void worker_rebind_fn(struct work_struct *work)
{
	struct worker *worker = container_of(work, struct worker, rebind_work);
	struct global_cwq *gcwq = worker->gcwq;

	if (worker_maybe_bind_and_lock(worker))
		worker_clr_flags(worker, WORKER_REBIND);

	spin_unlock_irq(&gcwq->lock);
}

static struct worker *alloc_worker(void)
{
	struct worker *worker;

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

/**
 * create_worker - create a new workqueue worker
 * @gcwq: gcwq the new worker will belong to
 * @bind: whether to set affinity to @cpu or not
 *
 * Create a new worker which is bound to @gcwq.  The returned worker
 * can be started by calling start_worker() or destroyed using
 * destroy_worker().
 *
 * CONTEXT:
 * Might sleep.  Does GFP_KERNEL allocations.
 *
 * RETURNS:
 * Pointer to the newly created worker.
 */
static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
{
	bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
	struct worker *worker = NULL;
	int id = -1;

	spin_lock_irq(&gcwq->lock);
	while (ida_get_new(&gcwq->worker_ida, &id)) {
		spin_unlock_irq(&gcwq->lock);
		if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
			goto fail;
		spin_lock_irq(&gcwq->lock);
	}
	spin_unlock_irq(&gcwq->lock);

	worker = alloc_worker();
	if (!worker)
		goto fail;

	worker->gcwq = gcwq;
	worker->id = id;

	if (!on_unbound_cpu)
		worker->task = kthread_create_on_node(worker_thread,
						      worker,
						      cpu_to_node(gcwq->cpu),
						      "kworker/%u:%d", gcwq->cpu, id);
	else
		worker->task = kthread_create(worker_thread, worker,
					      "kworker/u:%d", id);
	if (IS_ERR(worker->task))
		goto fail;

	/*
	 * A rogue worker will become a regular one if CPU comes
	 * online later on.  Make sure every worker has
	 * PF_THREAD_BOUND set.
	 */
	if (bind && !on_unbound_cpu)
		kthread_bind(worker->task, gcwq->cpu);
	else {
		worker->task->flags |= PF_THREAD_BOUND;
		if (on_unbound_cpu)
			worker->flags |= WORKER_UNBOUND;
	}

	return worker;
fail:
	if (id >= 0) {
		spin_lock_irq(&gcwq->lock);
		ida_remove(&gcwq->worker_ida, id);
		spin_unlock_irq(&gcwq->lock);
	}
	kfree(worker);
	return NULL;
}

/**
 * start_worker - start a newly created worker
 * @worker: worker to start
 *
 * Make the gcwq aware of @worker and start it.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 */
static void start_worker(struct worker *worker)
{
	worker->flags |= WORKER_STARTED;
	worker->gcwq->nr_workers++;
	worker_enter_idle(worker);
	wake_up_process(worker->task);
}

/**
 * destroy_worker - destroy a workqueue worker
 * @worker: worker to be destroyed
 *
 * Destroy @worker and adjust @gcwq stats accordingly.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
 */
static void destroy_worker(struct worker *worker)
{
	struct global_cwq *gcwq = worker->gcwq;
	int id = worker->id;

	/* sanity check frenzy */
	BUG_ON(worker->current_work);
	BUG_ON(!list_empty(&worker->scheduled));

	if (worker->flags & WORKER_STARTED)
		gcwq->nr_workers--;
	if (worker->flags & WORKER_IDLE)
		gcwq->nr_idle--;

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

	spin_unlock_irq(&gcwq->lock);

	kthread_stop(worker->task);
	kfree(worker);

	spin_lock_irq(&gcwq->lock);
	ida_remove(&gcwq->worker_ida, id);
}

static void idle_worker_timeout(unsigned long __gcwq)
{
	struct global_cwq *gcwq = (void *)__gcwq;

	spin_lock_irq(&gcwq->lock);

	if (too_many_workers(gcwq)) {
		struct worker *worker;
		unsigned long expires;

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

		if (time_before(jiffies, expires))
			mod_timer(&gcwq->idle_timer, expires);
		else {
			/* it's been idle for too long, wake up manager */
			gcwq->flags |= GCWQ_MANAGE_WORKERS;
			wake_up_worker(gcwq);
		}
	}

	spin_unlock_irq(&gcwq->lock);
}

static bool send_mayday(struct work_struct *work)
{
	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
	struct workqueue_struct *wq = cwq->wq;
	unsigned int cpu;

	if (!(wq->flags & WQ_RESCUER))
		return false;

	/* mayday mayday mayday */
	cpu = cwq->gcwq->cpu;
	/* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
	if (cpu == WORK_CPU_UNBOUND)
		cpu = 0;
	if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
		wake_up_process(wq->rescuer->task);
	return true;
}

static void gcwq_mayday_timeout(unsigned long __gcwq)
{
	struct global_cwq *gcwq = (void *)__gcwq;
	struct work_struct *work;

	spin_lock_irq(&gcwq->lock);

	if (need_to_create_worker(gcwq)) {
		/*
		 * 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, &gcwq->worklist, entry)
			send_mayday(work);
	}

	spin_unlock_irq(&gcwq->lock);

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

/**
 * maybe_create_worker - create a new worker if necessary
 * @gcwq: gcwq to create a new worker for
 *
 * Create a new worker for @gcwq if necessary.  @gcwq 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 @gcwq 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(gcwq->lock) which may be released and regrabbed
 * multiple times.  Does GFP_KERNEL allocations.  Called only from
 * manager.
 *
 * RETURNS:
 * false if no action was taken and gcwq->lock stayed locked, true
 * otherwise.
 */
static bool maybe_create_worker(struct global_cwq *gcwq)
__releases(&gcwq->lock)
__acquires(&gcwq->lock)
{
	if (!need_to_create_worker(gcwq))
		return false;
restart:
	spin_unlock_irq(&gcwq->lock);

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

	while (true) {
		struct worker *worker;

		worker = create_worker(gcwq, true);
		if (worker) {
			del_timer_sync(&gcwq->mayday_timer);
			spin_lock_irq(&gcwq->lock);
			start_worker(worker);
			BUG_ON(need_to_create_worker(gcwq));
			return true;
		}

		if (!need_to_create_worker(gcwq))
			break;

		__set_current_state(TASK_INTERRUPTIBLE);
		schedule_timeout(CREATE_COOLDOWN);

		if (!need_to_create_worker(gcwq))
			break;
	}

	del_timer_sync(&gcwq->mayday_timer);
	spin_lock_irq(&gcwq->lock);
	if (need_to_create_worker(gcwq))
		goto restart;
	return true;
}

/**
 * maybe_destroy_worker - destroy workers which have been idle for a while
 * @gcwq: gcwq to destroy workers for
 *
 * Destroy @gcwq workers which have been idle for longer than
 * IDLE_WORKER_TIMEOUT.
 *
 * LOCKING:
 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
 * multiple times.  Called only from manager.
 *
 * RETURNS:
 * false if no action was taken and gcwq->lock stayed locked, true
 * otherwise.
 */
static bool maybe_destroy_workers(struct global_cwq *gcwq)
{
	bool ret = false;

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

		worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
		expires = worker->last_active + IDLE_WORKER_TIMEOUT;

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

		destroy_worker(worker);
		ret = true;
	}

	return ret;
}

/**
 * manage_workers - manage worker pool
 * @worker: self
 *
 * Assume the manager role and manage gcwq worker pool @worker belongs
 * to.  At any given time, there can be only zero or one manager per
 * gcwq.  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(gcwq->lock) which may be released and regrabbed
 * multiple times.  Does GFP_KERNEL allocations.
 *
 * RETURNS:
 * false if no action was taken and gcwq->lock stayed locked, true if
 * some action was taken.
 */
static bool manage_workers(struct worker *worker)
{
	struct global_cwq *gcwq = worker->gcwq;
	bool ret = false;

	if (gcwq->flags & GCWQ_MANAGING_WORKERS)
		return ret;

	gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
	gcwq->flags |= GCWQ_MANAGING_WORKERS;

	/*
	 * Destroy and then create so that may_start_working() is true
	 * on return.
	 */
	ret |= maybe_destroy_workers(gcwq);
	ret |= maybe_create_worker(gcwq);

	gcwq->flags &= ~GCWQ_MANAGING_WORKERS;

	/*
	 * The trustee might be waiting to take over the manager
	 * position, tell it we're done.
	 */
	if (unlikely(gcwq->trustee))
		wake_up_all(&gcwq->trustee_wait);

	return ret;
}

/**
 * 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 paramter 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(gcwq->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;
}

static void cwq_activate_delayed_work(struct work_struct *work)
{
	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
	struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);

	trace_workqueue_activate_work(work);
	move_linked_works(work, pos, NULL);
	__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
	cwq->nr_active++;
}

static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
{
	struct work_struct *work = list_first_entry(&cwq->delayed_works,
						    struct work_struct, entry);

	cwq_activate_delayed_work(work);
}

/**
 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
 * @cwq: cwq of interest
 * @color: color of work which left the queue
 * @delayed: for a delayed work
 *
 * A work either has completed or is removed from pending queue,
 * decrement nr_in_flight of its cwq and handle workqueue flushing.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 */
static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
				 bool delayed)
{
	/* ignore uncolored works */
	if (color == WORK_NO_COLOR)
		return;

	cwq->nr_in_flight[color]--;

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

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

	/* are there still in-flight works? */
	if (cwq->nr_in_flight[color])
		return;

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

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

/**
 * 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(gcwq->lock) which is released and regrabbed.
 */
static void process_one_work(struct worker *worker, struct work_struct *work)
__releases(&gcwq->lock)
__acquires(&gcwq->lock)
{
	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
	struct global_cwq *gcwq = cwq->gcwq;
	struct hlist_head *bwh = busy_worker_head(gcwq, work);
	bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
	work_func_t f = work->func;
	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 = work->lockdep_map;
#endif
	/*
	 * 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(gcwq, bwh, work);
	if (unlikely(collision)) {
		move_linked_works(work, &collision->scheduled, NULL);
		return;
	}

	/* claim and process */
	debug_work_deactivate(work);
	hlist_add_head(&worker->hentry, bwh);
	worker->current_work = work;
	worker->current_cwq = cwq;
	work_color = get_work_color(work);

	/* record the current cpu number in the work data and dequeue */
	set_work_cpu(work, gcwq->cpu);
	list_del_init(&work->entry);

	/*
	 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
	 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
	 */
	if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
		struct work_struct *nwork = list_first_entry(&gcwq->worklist,
						struct work_struct, entry);

		if (!list_empty(&gcwq->worklist) &&
		    get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
			wake_up_worker(gcwq);
		else
			gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
	}

	/*
	 * CPU intensive works don't participate in concurrency
	 * management.  They're the scheduler's responsibility.
	 */
	if (unlikely(cpu_intensive))
		worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);

	spin_unlock_irq(&gcwq->lock);

	smp_wmb();	/* paired with test_and_set_bit(PENDING) */
	work_clear_pending(work);

	lock_map_acquire_read(&cwq->wq->lockdep_map);
	lock_map_acquire(&lockdep_map);
	trace_workqueue_execute_start(work);
	f(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(&cwq->wq->lockdep_map);

	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
		printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
		       "%s/0x%08x/%d\n",
		       current->comm, preempt_count(), task_pid_nr(current));
		printk(KERN_ERR "    last function: ");
		print_symbol("%s\n", (unsigned long)f);
		debug_show_held_locks(current);
		dump_stack();
	}

	spin_lock_irq(&gcwq->lock);

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

	/* we're done with it, release */
	hlist_del_init(&worker->hentry);
	worker->current_work = NULL;
	worker->current_cwq = NULL;
	cwq_dec_nr_in_flight(cwq, work_color, false);
}

/**
 * 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(gcwq->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 gcwq worker thread function.  There's a single dynamic pool of
 * these per each cpu.  These workers process all works regardless of
 * their specific target workqueue.  The only exception is works which
 * belong to workqueues with a rescuer which will be explained in
 * rescuer_thread().
 */
static int worker_thread(void *__worker)
{
	struct worker *worker = __worker;
	struct global_cwq *gcwq = worker->gcwq;

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

	/* DIE can be set only while we're idle, checking here is enough */
	if (worker->flags & WORKER_DIE) {
		spin_unlock_irq(&gcwq->lock);
		worker->task->flags &= ~PF_WQ_WORKER;
		return 0;
	}

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

	/* do we need to manage? */
	if (unlikely(!may_start_working(gcwq)) && 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.
	 */
	BUG_ON(!list_empty(&worker->scheduled));

	/*
	 * When control reaches this point, we're guaranteed to have
	 * at least one idle worker or that someone else has already
	 * assumed the manager role.
	 */
	worker_clr_flags(worker, WORKER_PREP);

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

		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(gcwq));

	worker_set_flags(worker, WORKER_PREP, false);
sleep:
	if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
		goto recheck;

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

/**
 * rescuer_thread - the rescuer thread function
 * @__wq: the associated workqueue
 *
 * Workqueue rescuer thread function.  There's one rescuer for each
 * workqueue which has WQ_RESCUER set.
 *
 * Regular work processing on a gcwq 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 gcwq summons rescuers of all
 * workqueues which have works queued on the gcwq and let them process
 * those works so that forward progress can be guaranteed.
 *
 * This should happen rarely.
 */
static int rescuer_thread(void *__wq)
{
	struct workqueue_struct *wq = __wq;
	struct worker *rescuer = wq->rescuer;
	struct list_head *scheduled = &rescuer->scheduled;
	bool is_unbound = wq->flags & WQ_UNBOUND;
	unsigned int cpu;

	set_user_nice(current, RESCUER_NICE_LEVEL);
repeat:
	set_current_state(TASK_INTERRUPTIBLE);

	if (kthread_should_stop()) {
		__set_current_state(TASK_RUNNING);
		return 0;
	}

	/*
	 * See whether any cpu is asking for help.  Unbounded
	 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
	 */
	for_each_mayday_cpu(cpu, wq->mayday_mask) {
		unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
		struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
		struct global_cwq *gcwq = cwq->gcwq;
		struct work_struct *work, *n;

		__set_current_state(TASK_RUNNING);
		mayday_clear_cpu(cpu, wq->mayday_mask);

		/* migrate to the target cpu if possible */
		rescuer->gcwq = gcwq;
		worker_maybe_bind_and_lock(rescuer);

		/*
		 * Slurp in all works issued via this workqueue and
		 * process'em.
		 */
		BUG_ON(!list_empty(&rescuer->scheduled));
		list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
			if (get_work_cwq(work) == cwq)
				move_linked_works(work, scheduled, &n);

		process_scheduled_works(rescuer);

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

		spin_unlock_irq(&gcwq->lock);
	}

	schedule();
	goto repeat;
}

struct wq_barrier {
	struct work_struct	work;
	struct completion	done;
};

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
 * @cwq: cwq 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 cwq from @target.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock).
 */
static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
			      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 gcwq->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);

	/*
	 * 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(cwq, &barr->work, head,
		    work_color_to_flags(WORK_NO_COLOR) | linked);
}

/**
 * flush_workqueue_prep_cwqs - prepare cwqs 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 cwqs for workqueue flushing.
 *
 * If @flush_color is non-negative, flush_color on all cwqs should be
 * -1.  If no cwq has in-flight commands at the specified color, all
 * cwq->flush_color's stay at -1 and %false is returned.  If any cwq
 * has in flight commands, its cwq->flush_color is set to
 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
 * 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 cwqs should have the same
 * work_color which is previous to @work_color and all will be
 * advanced to @work_color.
 *
 * CONTEXT:
 * mutex_lock(wq->flush_mutex).
 *
 * RETURNS:
 * %true if @flush_color >= 0 and there's something to flush.  %false
 * otherwise.
 */
static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
				      int flush_color, int work_color)
{
	bool wait = false;
	unsigned int cpu;

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

	for_each_cwq_cpu(cpu, wq) {
		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
		struct global_cwq *gcwq = cwq->gcwq;

		spin_lock_irq(&gcwq->lock);

		if (flush_color >= 0) {
			BUG_ON(cwq->flush_color != -1);

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

		if (work_color >= 0) {
			BUG_ON(work_color != work_next_color(cwq->work_color));
			cwq->work_color = work_color;
		}

		spin_unlock_irq(&gcwq->lock);
	}

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

	return wait;
}

/**
 * flush_workqueue - ensure that any scheduled work has run to completion.
 * @wq: workqueue to flush
 *
 * Forces execution of the workqueue and blocks until its completion.
 * This is typically used in driver shutdown handlers.
 *
 * We sleep until all works which were queued on entry have been handled,
 * but we are 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;

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

	mutex_lock(&wq->flush_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.
		 */
		BUG_ON(!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 */
			BUG_ON(wq->flush_color != this_flusher.flush_color);

			wq->first_flusher = &this_flusher;

			if (!flush_workqueue_prep_cwqs(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 */
			BUG_ON(wq->flush_color == this_flusher.flush_color);
			list_add_tail(&this_flusher.list, &wq->flusher_queue);
			flush_workqueue_prep_cwqs(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);
	}

	mutex_unlock(&wq->flush_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->flush_mutex);

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

	wq->first_flusher = NULL;

	BUG_ON(!list_empty(&this_flusher.list));
	BUG_ON(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);
		}

		BUG_ON(!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_cwqs(wq, -1, wq->work_color);
		}

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

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

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

		if (flush_workqueue_prep_cwqs(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->flush_mutex);
}
EXPORT_SYMBOL_GPL(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 detemined
 * 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;
	unsigned int cpu;

	/*
	 * __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.
	 */
	spin_lock(&workqueue_lock);
	if (!wq->nr_drainers++)
		wq->flags |= WQ_DRAINING;
	spin_unlock(&workqueue_lock);
reflush:
	flush_workqueue(wq);

	for_each_cwq_cpu(cpu, wq) {
		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
		bool drained;

		spin_lock_irq(&cwq->gcwq->lock);
		drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
		spin_unlock_irq(&cwq->gcwq->lock);

		if (drained)
			continue;

		if (++flush_cnt == 10 ||
		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
			pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
				   wq->name, flush_cnt);
		goto reflush;
	}

	spin_lock(&workqueue_lock);
	if (!--wq->nr_drainers)
		wq->flags &= ~WQ_DRAINING;
	spin_unlock(&workqueue_lock);
}
EXPORT_SYMBOL_GPL(drain_workqueue);

static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
			     bool wait_executing)
{
	struct worker *worker = NULL;
	struct global_cwq *gcwq;
	struct cpu_workqueue_struct *cwq;

	might_sleep();
	gcwq = get_work_gcwq(work);
	if (!gcwq)
		return false;

	spin_lock_irq(&gcwq->lock);
	if (!list_empty(&work->entry)) {
		/*
		 * See the comment near try_to_grab_pending()->smp_rmb().
		 * If it was re-queued to a different gcwq under us, we
		 * are not going to wait.
		 */
		smp_rmb();
		cwq = get_work_cwq(work);
		if (unlikely(!cwq || gcwq != cwq->gcwq))
			goto already_gone;
	} else if (wait_executing) {
		worker = find_worker_executing_work(gcwq, work);
		if (!worker)
			goto already_gone;
		cwq = worker->current_cwq;
	} else
		goto already_gone;

	insert_wq_barrier(cwq, barr, work, worker);
	spin_unlock_irq(&gcwq->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 (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
		lock_map_acquire(&cwq->wq->lockdep_map);
	else
		lock_map_acquire_read(&cwq->wq->lockdep_map);
	lock_map_release(&cwq->wq->lockdep_map);

	return true;
already_gone:
	spin_unlock_irq(&gcwq->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.  This function considers
 * only the last queueing instance of @work.  If @work has been
 * enqueued across different CPUs on a non-reentrant workqueue or on
 * multiple workqueues, @work might still be executing on return on
 * some of the CPUs from earlier queueing.
 *
 * If @work was queued only on a non-reentrant, ordered or unbound
 * workqueue, @work is guaranteed to be idle on return if it hasn't
 * been requeued since flush started.
 *
 * RETURNS:
 * %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 (start_flush_work(work, &barr, true)) {
		wait_for_completion(&barr.done);
		destroy_work_on_stack(&barr.work);
		return true;
	} else
		return false;
}
EXPORT_SYMBOL_GPL(flush_work);

static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
{
	struct wq_barrier barr;
	struct worker *worker;

	spin_lock_irq(&gcwq->lock);

	worker = find_worker_executing_work(gcwq, work);
	if (unlikely(worker))
		insert_wq_barrier(worker->current_cwq, &barr, work, worker);

	spin_unlock_irq(&gcwq->lock);

	if (unlikely(worker)) {
		wait_for_completion(&barr.done);
		destroy_work_on_stack(&barr.work);
		return true;
	} else
		return false;
}

static bool wait_on_work(struct work_struct *work)
{
	bool ret = false;
	int cpu;

	might_sleep();

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

	for_each_gcwq_cpu(cpu)
		ret |= wait_on_cpu_work(get_gcwq(cpu), work);
	return ret;
}

/**
 * flush_work_sync - wait until a work has finished execution
 * @work: the work to flush
 *
 * Wait until @work has finished execution.  On return, it's
 * guaranteed that all queueing instances of @work which happened
 * before this function is called are finished.  In other words, if
 * @work hasn't been requeued since this function was called, @work is
 * guaranteed to be idle on return.
 *
 * RETURNS:
 * %true if flush_work_sync() waited for the work to finish execution,
 * %false if it was already idle.
 */
bool flush_work_sync(struct work_struct *work)
{
	struct wq_barrier barr;
	bool pending, waited;

	/* we'll wait for executions separately, queue barr only if pending */
	pending = start_flush_work(work, &barr, false);

	/* wait for executions to finish */
	waited = wait_on_work(work);

	/* wait for the pending one */
	if (pending) {
		wait_for_completion(&barr.done);
		destroy_work_on_stack(&barr.work);
	}

	return pending || waited;
}
EXPORT_SYMBOL_GPL(flush_work_sync);

/*
 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
 * so this work can't be re-armed in any way.
 */
static int try_to_grab_pending(struct work_struct *work)
{
	struct global_cwq *gcwq;
	int ret = -1;

	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.
	 */
	gcwq = get_work_gcwq(work);
	if (!gcwq)
		return ret;

	spin_lock_irq(&gcwq->lock);
	if (!list_empty(&work->entry)) {
		/*
		 * This work is queued, but perhaps we locked the wrong gcwq.
		 * In that case we must see the new value after rmb(), see
		 * insert_work()->wmb().
		 */
		smp_rmb();
		if (gcwq == get_work_gcwq(work)) {
			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
			 * cwq->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)
				cwq_activate_delayed_work(work);

			list_del_init(&work->entry);
			cwq_dec_nr_in_flight(get_work_cwq(work),
				get_work_color(work),
				*work_data_bits(work) & WORK_STRUCT_DELAYED);
			ret = 1;
		}
	}
	spin_unlock_irq(&gcwq->lock);

	return ret;
}

static bool __cancel_work_timer(struct work_struct *work,
				struct timer_list* timer)
{
	int ret;

	do {
		ret = (timer && likely(del_timer(timer)));
		if (!ret)
			ret = try_to_grab_pending(work);
		wait_on_work(work);
	} while (unlikely(ret < 0));

	clear_work_data(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.
 *
 * RETURNS:
 * %true if @work was pending, %false otherwise.
 */
bool cancel_work_sync(struct work_struct *work)
{
	return __cancel_work_timer(work, NULL);
}
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.
 *
 * RETURNS:
 * %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)
{
	if (del_timer_sync(&dwork->timer))
		__queue_work(raw_smp_processor_id(),
			     get_work_cwq(&dwork->work)->wq, &dwork->work);
	return flush_work(&dwork->work);
}
EXPORT_SYMBOL(flush_delayed_work);

/**
 * flush_delayed_work_sync - wait for a dwork to finish
 * @dwork: the delayed work to flush
 *
 * Delayed timer is cancelled and the pending work is queued for
 * execution immediately.  Other than timer handling, its behavior
 * is identical to flush_work_sync().
 *
 * RETURNS:
 * %true if flush_work_sync() waited for the work to finish execution,
 * %false if it was already idle.
 */
bool flush_delayed_work_sync(struct delayed_work *dwork)
{
	if (del_timer_sync(&dwork->timer))
		__queue_work(raw_smp_processor_id(),
			     get_work_cwq(&dwork->work)->wq, &dwork->work);
	return flush_work_sync(&dwork->work);
}
EXPORT_SYMBOL(flush_delayed_work_sync);

/**
 * 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.
 *
 * RETURNS:
 * %true if @dwork was pending, %false otherwise.
 */
bool cancel_delayed_work_sync(struct delayed_work *dwork)
{
	return __cancel_work_timer(&dwork->work, &dwork->timer);
}
EXPORT_SYMBOL(cancel_delayed_work_sync);

/**
 * schedule_work - put work task in global workqueue
 * @work: job to be done
 *
 * Returns zero if @work was already on the kernel-global workqueue and
 * non-zero otherwise.
 *
 * This puts a job in the kernel-global workqueue if it was not already
 * queued and leaves it in the same position on the kernel-global
 * workqueue otherwise.
 */
int schedule_work(struct work_struct *work)
{
	return queue_work(system_wq, work);
}
EXPORT_SYMBOL(schedule_work);

/*
 * schedule_work_on - put work task on a specific cpu
 * @cpu: cpu to put the work task on
 * @work: job to be done
 *
 * This puts a job on a specific cpu
 */
int schedule_work_on(int cpu, struct work_struct *work)
{
	return queue_work_on(cpu, system_wq, work);
}
EXPORT_SYMBOL(schedule_work_on);

/**
 * schedule_delayed_work - put work task in global workqueue after delay
 * @dwork: job to be done
 * @delay: number of jiffies to wait or 0 for immediate execution
 *
 * After waiting for a given time this puts a job in the kernel-global
 * workqueue.
 */
int schedule_delayed_work(struct delayed_work *dwork,
					unsigned long delay)
{
	return queue_delayed_work(system_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work);

/**
 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 * @cpu: cpu to use
 * @dwork: job to be done
 * @delay: number of jiffies to wait
 *
 * After waiting for a given time this puts a job in the kernel-global
 * workqueue on the specified CPU.
 */
int schedule_delayed_work_on(int cpu,
			struct delayed_work *dwork, unsigned long delay)
{
	return queue_delayed_work_on(cpu, system_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work_on);

/**
 * 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.
 *
 * RETURNS:
 * 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;
}

/**
 * flush_scheduled_work - ensure that any scheduled work has run to completion.
 *
 * Forces execution of the kernel-global workqueue and blocks until its
 * completion.
 *
 * Think twice before calling this function!  It's very easy to get into
 * trouble if you don't take great care.  Either of the following situations
 * will lead to deadlock:
 *
 *	One of the work items currently on the workqueue needs to acquire
 *	a lock held by your code or its caller.
 *
 *	Your code is running in the context of a work routine.
 *
 * They will be detected by lockdep when they occur, but the first might not
 * occur very often.  It depends on what work items are on the workqueue and
 * what locks they need, which you have no control over.
 *
 * In most situations flushing the entire workqueue is overkill; you merely
 * need to know that a particular work item isn't queued and isn't running.
 * In such cases you should use cancel_delayed_work_sync() or
 * cancel_work_sync() instead.
 */
void flush_scheduled_work(void)
{
	flush_workqueue(system_wq);
}
EXPORT_SYMBOL(flush_scheduled_work);

/**
 * 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.
 *
 * Returns:	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);

int keventd_up(void)
{
	return system_wq != NULL;
}

static int alloc_cwqs(struct workqueue_struct *wq)
{
	/*
	 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
	 * Make sure that the alignment isn't lower than that of
	 * unsigned long long.
	 */
	const size_t size = sizeof(struct cpu_workqueue_struct);
	const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
				   __alignof__(unsigned long long));
#ifdef CONFIG_SMP
	bool percpu = !(wq->flags & WQ_UNBOUND);
#else
	bool percpu = false;
#endif

	if (percpu)
		wq->cpu_wq.pcpu = __alloc_percpu(size, align);
	else {
		void *ptr;

		/*
		 * Allocate enough room to align cwq and put an extra
		 * pointer at the end pointing back to the originally
		 * allocated pointer which will be used for free.
		 */
		ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
		if (ptr) {
			wq->cpu_wq.single = PTR_ALIGN(ptr, align);
			*(void **)(wq->cpu_wq.single + 1) = ptr;
		}
	}

	/* just in case, make sure it's actually aligned */
	BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
	return wq->cpu_wq.v ? 0 : -ENOMEM;
}

static void free_cwqs(struct workqueue_struct *wq)
{
#ifdef CONFIG_SMP
	bool percpu = !(wq->flags & WQ_UNBOUND);
#else
	bool percpu = false;
#endif

	if (percpu)
		free_percpu(wq->cpu_wq.pcpu);
	else if (wq->cpu_wq.single) {
		/* the pointer to free is stored right after the cwq */
		kfree(*(void **)(wq->cpu_wq.single + 1));
	}
}

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)
		printk(KERN_WARNING "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 *name,
					       unsigned int flags,
					       int max_active,
					       struct lock_class_key *key,
					       const char *lock_name)
{
	struct workqueue_struct *wq;
	unsigned int cpu;

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

	/*
	 * Unbound workqueues aren't concurrency managed and should be
	 * dispatched to workers immediately.
	 */
	if (flags & WQ_UNBOUND)
		flags |= WQ_HIGHPRI;

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

	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
	if (!wq)
		goto err;

	wq->flags = flags;
	wq->saved_max_active = max_active;
	mutex_init(&wq->flush_mutex);
	atomic_set(&wq->nr_cwqs_to_flush, 0);
	INIT_LIST_HEAD(&wq->flusher_queue);
	INIT_LIST_HEAD(&wq->flusher_overflow);

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

	if (alloc_cwqs(wq) < 0)
		goto err;

	for_each_cwq_cpu(cpu, wq) {
		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
		struct global_cwq *gcwq = get_gcwq(cpu);

		BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
		cwq->gcwq = gcwq;
		cwq->wq = wq;
		cwq->flush_color = -1;
		cwq->max_active = max_active;
		INIT_LIST_HEAD(&cwq->delayed_works);
	}

	if (flags & WQ_RESCUER) {
		struct worker *rescuer;

		if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
			goto err;

		wq->rescuer = rescuer = alloc_worker();
		if (!rescuer)
			goto err;

		rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
		if (IS_ERR(rescuer->task))
			goto err;

		rescuer->task->flags |= PF_THREAD_BOUND;
		wake_up_process(rescuer->task);
	}

	/*
	 * workqueue_lock protects global freeze state and workqueues
	 * list.  Grab it, set max_active accordingly and add the new
	 * workqueue to workqueues list.
	 */
	spin_lock(&workqueue_lock);

	if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
		for_each_cwq_cpu(cpu, wq)
			get_cwq(cpu, wq)->max_active = 0;

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

	spin_unlock(&workqueue_lock);

	return wq;
err:
	if (wq) {
		free_cwqs(wq);
		free_mayday_mask(wq->mayday_mask);
		kfree(wq->rescuer);
		kfree(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)
{
	unsigned int cpu;

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

	/*
	 * wq list is used to freeze wq, remove from list after
	 * flushing is complete in case freeze races us.
	 */
	spin_lock(&workqueue_lock);
	list_del(&wq->list);
	spin_unlock(&workqueue_lock);

	/* sanity check */
	for_each_cwq_cpu(cpu, wq) {
		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
		int i;

		for (i = 0; i < WORK_NR_COLORS; i++)
			BUG_ON(cwq->nr_in_flight[i]);
		BUG_ON(cwq->nr_active);
		BUG_ON(!list_empty(&cwq->delayed_works));
	}

	if (wq->flags & WQ_RESCUER) {
		kthread_stop(wq->rescuer->task);
		free_mayday_mask(wq->mayday_mask);
		kfree(wq->rescuer);
	}

	free_cwqs(wq);
	kfree(wq);
}
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)
{
	unsigned int cpu;

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

	spin_lock(&workqueue_lock);

	wq->saved_max_active = max_active;

	for_each_cwq_cpu(cpu, wq) {
		struct global_cwq *gcwq = get_gcwq(cpu);

		spin_lock_irq(&gcwq->lock);

		if (!(wq->flags & WQ_FREEZABLE) ||
		    !(gcwq->flags & GCWQ_FREEZING))
			get_cwq(gcwq->cpu, wq)->max_active = max_active;

		spin_unlock_irq(&gcwq->lock);
	}

	spin_unlock(&workqueue_lock);
}
EXPORT_SYMBOL_GPL(workqueue_set_max_active);

/**
 * 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.
 *
 * RETURNS:
 * %true if congested, %false otherwise.
 */
bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
{
	struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);

	return !list_empty(&cwq->delayed_works);
}
EXPORT_SYMBOL_GPL(workqueue_congested);

/**
 * work_cpu - return the last known associated cpu for @work
 * @work: the work of interest
 *
 * RETURNS:
 * CPU number if @work was ever queued.  WORK_CPU_NONE otherwise.
 */
unsigned int work_cpu(struct work_struct *work)
{
	struct global_cwq *gcwq = get_work_gcwq(work);

	return gcwq ? gcwq->cpu : WORK_CPU_NONE;
}
EXPORT_SYMBOL_GPL(work_cpu);

/**
 * 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.
 * Especially for reentrant wqs, the pending state might hide the
 * running state.
 *
 * RETURNS:
 * OR'd bitmask of WORK_BUSY_* bits.
 */
unsigned int work_busy(struct work_struct *work)
{
	struct global_cwq *gcwq = get_work_gcwq(work);
	unsigned long flags;
	unsigned int ret = 0;

	if (!gcwq)
		return false;

	spin_lock_irqsave(&gcwq->lock, flags);

	if (work_pending(work))
		ret |= WORK_BUSY_PENDING;
	if (find_worker_executing_work(gcwq, work))
		ret |= WORK_BUSY_RUNNING;

	spin_unlock_irqrestore(&gcwq->lock, flags);

	return ret;
}
EXPORT_SYMBOL_GPL(work_busy);

/*
 * CPU hotplug.
 *
 * There are two challenges in supporting CPU hotplug.  Firstly, there
 * are a lot of assumptions on strong associations among work, cwq and
 * gcwq which make migrating pending and scheduled works very
 * difficult to implement without impacting hot paths.  Secondly,
 * gcwqs serve mix of short, long and very long running works making
 * blocked draining impractical.
 *
 * This is solved by allowing a gcwq to be detached from CPU, running
 * it with unbound (rogue) workers and allowing it to be reattached
 * later if the cpu comes back online.  A separate thread is created
 * to govern a gcwq in such state and is called the trustee of the
 * gcwq.
 *
 * Trustee states and their descriptions.
 *
 * START	Command state used on startup.  On CPU_DOWN_PREPARE, a
 *		new trustee is started with this state.
 *
 * IN_CHARGE	Once started, trustee will enter this state after
 *		assuming the manager role and making all existing
 *		workers rogue.  DOWN_PREPARE waits for trustee to
 *		enter this state.  After reaching IN_CHARGE, trustee
 *		tries to execute the pending worklist until it's empty
 *		and the state is set to BUTCHER, or the state is set
 *		to RELEASE.
 *
 * BUTCHER	Command state which is set by the cpu callback after
 *		the cpu has went down.  Once this state is set trustee
 *		knows that there will be no new works on the worklist
 *		and once the worklist is empty it can proceed to
 *		killing idle workers.
 *
 * RELEASE	Command state which is set by the cpu callback if the
 *		cpu down has been canceled or it has come online
 *		again.  After recognizing this state, trustee stops
 *		trying to drain or butcher and clears ROGUE, rebinds
 *		all remaining workers back to the cpu and releases
 *		manager role.
 *
 * DONE		Trustee will enter this state after BUTCHER or RELEASE
 *		is complete.
 *
 *          trustee                 CPU                draining
 *         took over                down               complete
 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
 *                        |                     |                  ^
 *                        | CPU is back online  v   return workers |
 *                         ----------------> RELEASE --------------
 */

/**
 * trustee_wait_event_timeout - timed event wait for trustee
 * @cond: condition to wait for
 * @timeout: timeout in jiffies
 *
 * wait_event_timeout() for trustee to use.  Handles locking and
 * checks for RELEASE request.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
 * multiple times.  To be used by trustee.
 *
 * RETURNS:
 * Positive indicating left time if @cond is satisfied, 0 if timed
 * out, -1 if canceled.
 */
#define trustee_wait_event_timeout(cond, timeout) ({			\
	long __ret = (timeout);						\
	while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) &&	\
	       __ret) {							\
		spin_unlock_irq(&gcwq->lock);				\
		__wait_event_timeout(gcwq->trustee_wait, (cond) ||	\
			(gcwq->trustee_state == TRUSTEE_RELEASE),	\
			__ret);						\
		spin_lock_irq(&gcwq->lock);				\
	}								\
	gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret);		\
})

/**
 * trustee_wait_event - event wait for trustee
 * @cond: condition to wait for
 *
 * wait_event() for trustee to use.  Automatically handles locking and
 * checks for CANCEL request.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
 * multiple times.  To be used by trustee.
 *
 * RETURNS:
 * 0 if @cond is satisfied, -1 if canceled.
 */
#define trustee_wait_event(cond) ({					\
	long __ret1;							\
	__ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
	__ret1 < 0 ? -1 : 0;						\
})

static int __cpuinit trustee_thread(void *__gcwq)
{
	struct global_cwq *gcwq = __gcwq;
	struct worker *worker;
	struct work_struct *work;
	struct hlist_node *pos;
	long rc;
	int i;

	BUG_ON(gcwq->cpu != smp_processor_id());

	spin_lock_irq(&gcwq->lock);
	/*
	 * Claim the manager position and make all workers rogue.
	 * Trustee must be bound to the target cpu and can't be
	 * cancelled.
	 */
	BUG_ON(gcwq->cpu != smp_processor_id());
	rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
	BUG_ON(rc < 0);

	gcwq->flags |= GCWQ_MANAGING_WORKERS;

	list_for_each_entry(worker, &gcwq->idle_list, entry)
		worker->flags |= WORKER_ROGUE;

	for_each_busy_worker(worker, i, pos, gcwq)
		worker->flags |= WORKER_ROGUE;

	/*
	 * Call schedule() so that we cross rq->lock and thus can
	 * guarantee sched callbacks see the rogue flag.  This is
	 * necessary as scheduler callbacks may be invoked from other
	 * cpus.
	 */
	spin_unlock_irq(&gcwq->lock);
	schedule();
	spin_lock_irq(&gcwq->lock);

	/*
	 * Sched callbacks are disabled now.  Zap nr_running.  After
	 * this, nr_running stays zero and need_more_worker() and
	 * keep_working() are always true as long as the worklist is
	 * not empty.
	 */
	atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);

	spin_unlock_irq(&gcwq->lock);
	del_timer_sync(&gcwq->idle_timer);
	spin_lock_irq(&gcwq->lock);

	/*
	 * We're now in charge.  Notify and proceed to drain.  We need
	 * to keep the gcwq running during the whole CPU down
	 * procedure as other cpu hotunplug callbacks may need to
	 * flush currently running tasks.
	 */
	gcwq->trustee_state = TRUSTEE_IN_CHARGE;
	wake_up_all(&gcwq->trustee_wait);

	/*
	 * The original cpu is in the process of dying and may go away
	 * anytime now.  When that happens, we and all workers would
	 * be migrated to other cpus.  Try draining any left work.  We
	 * want to get it over with ASAP - spam rescuers, wake up as
	 * many idlers as necessary and create new ones till the
	 * worklist is empty.  Note that if the gcwq is frozen, there
	 * may be frozen works in freezable cwqs.  Don't declare
	 * completion while frozen.
	 */
	while (gcwq->nr_workers != gcwq->nr_idle ||
	       gcwq->flags & GCWQ_FREEZING ||
	       gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
		int nr_works = 0;

		list_for_each_entry(work, &gcwq->worklist, entry) {
			send_mayday(work);
			nr_works++;
		}

		list_for_each_entry(worker, &gcwq->idle_list, entry) {
			if (!nr_works--)
				break;
			wake_up_process(worker->task);
		}

		if (need_to_create_worker(gcwq)) {
			spin_unlock_irq(&gcwq->lock);
			worker = create_worker(gcwq, false);
			spin_lock_irq(&gcwq->lock);
			if (worker) {
				worker->flags |= WORKER_ROGUE;
				start_worker(worker);
			}
		}

		/* give a breather */
		if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
			break;
	}

	/*
	 * Either all works have been scheduled and cpu is down, or
	 * cpu down has already been canceled.  Wait for and butcher
	 * all workers till we're canceled.
	 */
	do {
		rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
		while (!list_empty(&gcwq->idle_list))
			destroy_worker(list_first_entry(&gcwq->idle_list,
							struct worker, entry));
	} while (gcwq->nr_workers && rc >= 0);

	/*
	 * At this point, either draining has completed and no worker
	 * is left, or cpu down has been canceled or the cpu is being
	 * brought back up.  There shouldn't be any idle one left.
	 * Tell the remaining busy ones to rebind once it finishes the
	 * currently scheduled works by scheduling the rebind_work.
	 */
	WARN_ON(!list_empty(&gcwq->idle_list));

	for_each_busy_worker(worker, i, pos, gcwq) {
		struct work_struct *rebind_work = &worker->rebind_work;
		unsigned long worker_flags = worker->flags;

		/*
		 * Rebind_work may race with future cpu hotplug
		 * operations.  Use a separate flag to mark that
		 * rebinding is scheduled.  The morphing should
		 * be atomic.
		 */
		worker_flags |= WORKER_REBIND;
		worker_flags &= ~WORKER_ROGUE;
		ACCESS_ONCE(worker->flags) = worker_flags;

		/* queue rebind_work, wq doesn't matter, use the default one */
		if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
				     work_data_bits(rebind_work)))
			continue;

		debug_work_activate(rebind_work);
		insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
			    worker->scheduled.next,
			    work_color_to_flags(WORK_NO_COLOR));
	}

	/* relinquish manager role */
	gcwq->flags &= ~GCWQ_MANAGING_WORKERS;

	/* notify completion */
	gcwq->trustee = NULL;
	gcwq->trustee_state = TRUSTEE_DONE;
	wake_up_all(&gcwq->trustee_wait);
	spin_unlock_irq(&gcwq->lock);
	return 0;
}

/**
 * wait_trustee_state - wait for trustee to enter the specified state
 * @gcwq: gcwq the trustee of interest belongs to
 * @state: target state to wait for
 *
 * Wait for the trustee to reach @state.  DONE is already matched.
 *
 * CONTEXT:
 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
 * multiple times.  To be used by cpu_callback.
 */
static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
__releases(&gcwq->lock)
__acquires(&gcwq->lock)
{
	if (!(gcwq->trustee_state == state ||
	      gcwq->trustee_state == TRUSTEE_DONE)) {
		spin_unlock_irq(&gcwq->lock);
		__wait_event(gcwq->trustee_wait,
			     gcwq->trustee_state == state ||
			     gcwq->trustee_state == TRUSTEE_DONE);
		spin_lock_irq(&gcwq->lock);
	}
}

static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
						unsigned long action,
						void *hcpu)
{
	unsigned int cpu = (unsigned long)hcpu;
	struct global_cwq *gcwq = get_gcwq(cpu);
	struct task_struct *new_trustee = NULL;
	struct worker *uninitialized_var(new_worker);
	unsigned long flags;

	action &= ~CPU_TASKS_FROZEN;

	switch (action) {
	case CPU_DOWN_PREPARE:
		new_trustee = kthread_create(trustee_thread, gcwq,
					     "workqueue_trustee/%d\n", cpu);
		if (IS_ERR(new_trustee))
			return notifier_from_errno(PTR_ERR(new_trustee));
		kthread_bind(new_trustee, cpu);
		/* fall through */
	case CPU_UP_PREPARE:
		BUG_ON(gcwq->first_idle);
		new_worker = create_worker(gcwq, false);
		if (!new_worker) {
			if (new_trustee)
				kthread_stop(new_trustee);
			return NOTIFY_BAD;
		}
	}

	/* some are called w/ irq disabled, don't disturb irq status */
	spin_lock_irqsave(&gcwq->lock, flags);

	switch (action) {
	case CPU_DOWN_PREPARE:
		/* initialize trustee and tell it to acquire the gcwq */
		BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
		gcwq->trustee = new_trustee;
		gcwq->trustee_state = TRUSTEE_START;
		wake_up_process(gcwq->trustee);
		wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
		/* fall through */
	case CPU_UP_PREPARE:
		BUG_ON(gcwq->first_idle);
		gcwq->first_idle = new_worker;
		break;

	case CPU_DYING:
		/*
		 * Before this, the trustee and all workers except for
		 * the ones which are still executing works from
		 * before the last CPU down must be on the cpu.  After
		 * this, they'll all be diasporas.
		 */
		gcwq->flags |= GCWQ_DISASSOCIATED;
		break;

	case CPU_POST_DEAD:
		gcwq->trustee_state = TRUSTEE_BUTCHER;
		/* fall through */
	case CPU_UP_CANCELED:
		destroy_worker(gcwq->first_idle);
		gcwq->first_idle = NULL;
		break;

	case CPU_DOWN_FAILED:
	case CPU_ONLINE:
		gcwq->flags &= ~GCWQ_DISASSOCIATED;
		if (gcwq->trustee_state != TRUSTEE_DONE) {
			gcwq->trustee_state = TRUSTEE_RELEASE;
			wake_up_process(gcwq->trustee);
			wait_trustee_state(gcwq, TRUSTEE_DONE);
		}

		/*
		 * Trustee is done and there might be no worker left.
		 * Put the first_idle in and request a real manager to
		 * take a look.
		 */
		spin_unlock_irq(&gcwq->lock);
		kthread_bind(gcwq->first_idle->task, cpu);
		spin_lock_irq(&gcwq->lock);
		gcwq->flags |= GCWQ_MANAGE_WORKERS;
		start_worker(gcwq->first_idle);
		gcwq->first_idle = NULL;
		break;
	}

	spin_unlock_irqrestore(&gcwq->lock, flags);

	return notifier_from_errno(0);
}

/*
 * Workqueues should be brought up before normal priority CPU notifiers.
 * This will be registered high priority CPU notifier.
 */
static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
					       unsigned long action,
					       void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_UP_PREPARE:
	case CPU_UP_CANCELED:
	case CPU_DOWN_FAILED:
	case CPU_ONLINE:
		return workqueue_cpu_callback(nfb, action, hcpu);
	}
	return NOTIFY_OK;
}

/*
 * Workqueues should be brought down after normal priority CPU notifiers.
 * This will be registered as low priority CPU notifier.
 */
static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
						 unsigned long action,
						 void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DOWN_PREPARE:
	case CPU_DYING:
	case CPU_POST_DEAD:
		return workqueue_cpu_callback(nfb, action, hcpu);
	}
	return NOTIFY_OK;
}

#ifdef CONFIG_SMP

struct work_for_cpu {
	struct work_struct work;
	long (*fn)(void *);
	void *arg;
	long ret;
};

static void work_for_cpu_fn(struct work_struct *work)
{
	struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);

	wfc->ret = wfc->fn(wfc->arg);
}

/**
 * work_on_cpu - run a function in user context on a particular cpu
 * @cpu: the cpu to run on
 * @fn: the function to run
 * @arg: the function arg
 *
 * This will return the value @fn returns.
 * It is up to the caller to ensure that the cpu doesn't go offline.
 * The caller must not hold any locks which would prevent @fn from completing.
 */
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
{
	struct work_for_cpu wfc = { .fn = fn, .arg = arg };

	INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
	schedule_work_on(cpu, &wfc.work);
	flush_work(&wfc.work);
	return wfc.ret;
}
EXPORT_SYMBOL_GPL(work_on_cpu);
#endif /* CONFIG_SMP */

#ifdef CONFIG_FREEZER

/**
 * freeze_workqueues_begin - begin freezing workqueues
 *
 * Start freezing workqueues.  After this function returns, all freezable
 * workqueues will queue new works to their frozen_works list instead of
 * gcwq->worklist.
 *
 * CONTEXT:
 * Grabs and releases workqueue_lock and gcwq->lock's.
 */
void freeze_workqueues_begin(void)
{
	unsigned int cpu;

	spin_lock(&workqueue_lock);

	BUG_ON(workqueue_freezing);
	workqueue_freezing = true;

	for_each_gcwq_cpu(cpu) {
		struct global_cwq *gcwq = get_gcwq(cpu);
		struct workqueue_struct *wq;

		spin_lock_irq(&gcwq->lock);

		BUG_ON(gcwq->flags & GCWQ_FREEZING);
		gcwq->flags |= GCWQ_FREEZING;

		list_for_each_entry(wq, &workqueues, list) {
			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);

			if (cwq && wq->flags & WQ_FREEZABLE)
				cwq->max_active = 0;
		}

		spin_unlock_irq(&gcwq->lock);
	}

	spin_unlock(&workqueue_lock);
}

/**
 * freeze_workqueues_busy - are freezable workqueues still busy?
 *
 * Check whether freezing is complete.  This function must be called
 * between freeze_workqueues_begin() and thaw_workqueues().
 *
 * CONTEXT:
 * Grabs and releases workqueue_lock.
 *
 * RETURNS:
 * %true if some freezable workqueues are still busy.  %false if freezing
 * is complete.
 */
bool freeze_workqueues_busy(void)
{
	unsigned int cpu;
	bool busy = false;

	spin_lock(&workqueue_lock);

	BUG_ON(!workqueue_freezing);

	for_each_gcwq_cpu(cpu) {
		struct workqueue_struct *wq;
		/*
		 * nr_active is monotonically decreasing.  It's safe
		 * to peek without lock.
		 */
		list_for_each_entry(wq, &workqueues, list) {
			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);

			if (!cwq || !(wq->flags & WQ_FREEZABLE))
				continue;

			BUG_ON(cwq->nr_active < 0);
			if (cwq->nr_active) {
				busy = true;
				goto out_unlock;
			}
		}
	}
out_unlock:
	spin_unlock(&workqueue_lock);
	return busy;
}

/**
 * thaw_workqueues - thaw workqueues
 *
 * Thaw workqueues.  Normal queueing is restored and all collected
 * frozen works are transferred to their respective gcwq worklists.
 *
 * CONTEXT:
 * Grabs and releases workqueue_lock and gcwq->lock's.
 */
void thaw_workqueues(void)
{
	unsigned int cpu;

	spin_lock(&workqueue_lock);

	if (!workqueue_freezing)
		goto out_unlock;

	for_each_gcwq_cpu(cpu) {
		struct global_cwq *gcwq = get_gcwq(cpu);
		struct workqueue_struct *wq;

		spin_lock_irq(&gcwq->lock);

		BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
		gcwq->flags &= ~GCWQ_FREEZING;

		list_for_each_entry(wq, &workqueues, list) {
			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);

			if (!cwq || !(wq->flags & WQ_FREEZABLE))
				continue;

			/* restore max_active and repopulate worklist */
			cwq->max_active = wq->saved_max_active;

			while (!list_empty(&cwq->delayed_works) &&
			       cwq->nr_active < cwq->max_active)
				cwq_activate_first_delayed(cwq);
		}

		wake_up_worker(gcwq);

		spin_unlock_irq(&gcwq->lock);
	}

	workqueue_freezing = false;
out_unlock:
	spin_unlock(&workqueue_lock);
}
#endif /* CONFIG_FREEZER */

static int __init init_workqueues(void)
{
	unsigned int cpu;
	int i;

	cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
	cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);

	/* initialize gcwqs */
	for_each_gcwq_cpu(cpu) {
		struct global_cwq *gcwq = get_gcwq(cpu);

		spin_lock_init(&gcwq->lock);
		INIT_LIST_HEAD(&gcwq->worklist);
		gcwq->cpu = cpu;
		gcwq->flags |= GCWQ_DISASSOCIATED;

		INIT_LIST_HEAD(&gcwq->idle_list);
		for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
			INIT_HLIST_HEAD(&gcwq->busy_hash[i]);

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

		setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
			    (unsigned long)gcwq);

		ida_init(&gcwq->worker_ida);

		gcwq->trustee_state = TRUSTEE_DONE;
		init_waitqueue_head(&gcwq->trustee_wait);
	}

	/* create the initial worker */
	for_each_online_gcwq_cpu(cpu) {
		struct global_cwq *gcwq = get_gcwq(cpu);
		struct worker *worker;

		if (cpu != WORK_CPU_UNBOUND)
			gcwq->flags &= ~GCWQ_DISASSOCIATED;
		worker = create_worker(gcwq, true);
		BUG_ON(!worker);
		spin_lock_irq(&gcwq->lock);
		start_worker(worker);
		spin_unlock_irq(&gcwq->lock);
	}

	system_wq = alloc_workqueue("events", 0, 0);
	system_long_wq = alloc_workqueue("events_long", 0, 0);
	system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
					    WQ_UNBOUND_MAX_ACTIVE);
	system_freezable_wq = alloc_workqueue("events_freezable",
					      WQ_FREEZABLE, 0);
	system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable",
			WQ_NON_REENTRANT | WQ_FREEZABLE, 0);
	BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
	       !system_unbound_wq || !system_freezable_wq ||
		!system_nrt_freezable_wq);
	return 0;
}
early_initcall(init_workqueues);