Date:	Fri, 26 Dec 2014 17:37:11 +0800
From:	Neil Zhang <glacier1980@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...hat.com>, peterz@...radead.org
Subject: panic at rb_next when do pick_next_task_fair because of rb_leftmost
 is NULL

Hi All,
I encountered the following crash in 3.10.24.

The panic log is as following.
The strange thing is that the nr_running change to NULL after pass the
check in the beginning of pick_next_task_fair.
So it seems there are race condition in the code.
Seems no related patch to fix it in the mainline.
Does anyone can help it?

struct rq {
lock = {
raw_lock = {
{
slock = 1463113524,
tickets = {
owner = 22324,
next = 22325
}
}
}
},
nr_running = 0,
cpu_load = {0, 0, 3, 33, 72},
last_load_update_tick = 83021764,
nohz_stamp = 0,
nohz_flags = 1,
skip_clock_update = 0,
nr_last_stamp = 83321795255303,
nr_running_integral = 54283347762368512,
ave_seqcnt = {
sequence = 690446180
},
load = {
weight = 0,
inv_weight = 0
},
nr_load_updates = 51751174,
nr_switches = 290795987,
cfs = {
load = {
weight = 0,
inv_weight = 0
},
nr_running = 0,
h_nr_running = 0,
exec_clock = 17025953367624,
min_vruntime = 125082978146967,
min_vruntime_copy = 125082978146967,
tasks_timeline = {
rb_node = 0x0
},
rb_leftmost = 0x0,
curr = 0x0,
next = 0x0,
last = 0x0,
skip = 0x0,
nr_spread_over = 57488,
runnable_load_avg = 0,

[83321.795281] c0 2084 (v.airplayserver) Unable to handle kernel NULL
pointer dereference at virtual address 00000008
[83321.795286] c0 2084 (v.airplayserver) pgd = ea858000
[83321.795293] c0 2084 (v.airplayserver) [00000008] *pgd=00000000
[83321.795306] c0 2084 (v.airplayserver) Internal error: Oops: 205
[#1] PREEMPT SMP ARM
[83321.795315] c0 2084 (v.airplayserver) Modules linked in:
[83321.795324] c0 2084 (v.airplayserver) CPU: 0 PID: 2084 Comm:
v.airplayserver Not tainted 3.10.24-gc7b472f #1
[83321.795329] c0 2084 (v.airplayserver) task: ce1f1ac0 ti: ce156000
task.ti: ce156000
[83321.795349] c0 2084 (v.airplayserver) PC is at rb_next+0x0/0x60
[83321.795363] c0 2084 (v.airplayserver) LR is at
pick_next_task_fair+0x10c/0x138
[83321.795368] c0 2084 (v.airplayserver) pc : [<c02c22f0>] lr :
[<c00973a0>] psr: 60060093
sp : ce157e18 ip : 00000000 fp : ce157edc
[83321.795371] c0 2084 (v.airplayserver) r10: c54474c0 r9 : c0c644c0
r8 : ce157f20
[83321.795376] c0 2084 (v.airplayserver) r7 : c54474c0 r6 : 00000000
r5 : 00000000 r4 : c5447518
[83321.795380] c0 2084 (v.airplayserver) r3 : c0097294 r2 : c54478f8
r1 : 00000000 r0 : 00000008
[83321.795388] c0 2084 (v.airplayserver) Flags: nZCv IRQs off FIQs on
Mode SVC_32 ISA ARM Segment user
[83321.795392] c0 2084 (v.airplayserver) Control: 30c5387d Table:
aa858000 DAC: fffffffd
[83321.795396] c0 2084 (v.airplayserver)
PC: 0xc02c2270:
[83321.795419] c0 2084 (v.airplayserver) 2270 1a000001 ea000004
e1a00003 e5903004 e3530000 1afffffb e12fff1e e12fff1e
[83321.795439] c0 2084 (v.airplayserver) 2290 e1a03001 e5901000
e3d11003 05823000 0a000003 e5912008 e1500002 05813008
[83321.795461] c0 2084 (v.airplayserver) 22b0 15813004 e5902008
e3520000 15921000 12011001 11831001 15821000 e5902004
[83321.795483] c0 2084 (v.airplayserver) 22d0 e3520000 15921000
12011001 11831001 15821000 e8900007 e8830007 e12fff1e
[83321.795504] c0 2084 (v.airplayserver) 22f0 e5902000 e1500002
0a000012 e5903004 e3530000 1a000001 ea000006 e1a03002
[83321.795526] c0 2084 (v.airplayserver) 2310 e5932008 e3520000
1afffffb e1a00003 e12fff1e e5932000 e3d23003 0afffffa
[83321.795546] c0 2084 (v.airplayserver) 2330 e5932004 e1500002
e1a00003 0afffff8 e1a00003 e12fff1e e3a03000 eafffff2
[83321.795568] c0 2084 (v.airplayserver) 2350 e5902000 e1500002
0a000012 e5903008 e3530000 1a000001 ea000006 e1a03002
[83321.795572] c0 2084 (v.airplayserver)
LR: 0xc0097320:
[83321.795592] c0 2084 (v.airplayserver) 7320 e5954128 e3540000
1affffe1 e59f3090 e2455038 e5933000 e3130080 0a000013
[83321.795612] c0 2084 (v.airplayserver) 7340 e59734e4 e283101f
e3530000 e203201f b1a03001 e59f106c e1a032c3 e5911000
[83321.795635] c0 2084 (v.airplayserver) 7360 e7913103 e1a03233
e3130001 0a000007 e597355c e5933000 e5933018 e3530000
[83321.795657] c0 2084 (v.airplayserver) 7380 0a000002 e1a00007
e1a01005 ebfffe2a e1a00005 e8bd80f8 e2860008 eb08abd3
[83321.795681] c0 2084 (v.airplayserver) 73a0 e3500000 0affffc9
e2405008 e1a01006 e1a00005 ebffff0d e3500000 c1a05006
[83321.795702] c0 2084 (v.airplayserver) 73c0 eaffffc2 c0c9b4b4
c08945bc e92d00f0 e52de004 e8bd4000 e3a02020 e3a03000
[83321.795724] c0 2084 (v.airplayserver) 73e0 e1530001 01520000
3a000004 e59f30ec e0830100 e59000e4 e8bd00f0 e12fff1e
[83321.795746] c0 2084 (v.airplayserver) 7400 e3510000 03500f56
8a00002e e1a04000 e1a05001 e3e0601f e3e07000 e3a0c000
[83321.795751] c0 2084 (v.airplayserver)
SP: 0xce157d98:
[83321.795771] c0 2084 (v.airplayserver) 7d98 ed711dc0 00000000
00000000 00000000 c54474c0 00000000 00000000 00000002
[83321.795795] c0 2084 (v.airplayserver) 7db8 c02c22f0 60060093
ffffffff ce157e04 ce157f20 c000ead8 00000008 00000000
[83321.795815] c0 2084 (v.airplayserver) 7dd8 c54478f8 c0097294
c5447518 00000000 00000000 c54474c0 ce157f20 c0c644c0
[83321.795838] c0 2084 (v.airplayserver) 7df8 c54474c0 ce157edc
00000000 ce157e18 c00973a0 c02c22f0 60060093 ffffffff
[83321.795861] c0 2084 (v.airplayserver) 7e18 c0097294 ce1f1d94
c089595c ce156000 ce1f1ac0 c08880d4 ce157e90 fab25188
[83321.795881] c0 2084 (v.airplayserver) 7e38 00004bc7 ce157f20
ce156000 ce157f20 c54449b8 00000000 c08870e8 c0c644c0
[83321.795903] c0 2084 (v.airplayserver) 7e58 c0c644c0 c0c644c0
c0c644c0 c0c644c0 00000000 c0087120 c0c61980 00000000
[83321.795928] c0 2084 (v.airplayserver) 7e78 fab18e38 00004bc7
ce156000 c0c61980 00000000 c008745c dc2d0e38 00004bc7
[83321.795930] c0 2084 (v.airplayserver)
FP: 0xce157e5c:
[83321.795951] c0 2084 (v.airplayserver) 7e5c c0c644c0 c0c644c0
c0c644c0 00000000 c0087120 c0c61980 00000000 fab18e38
[83321.795973] c0 2084 (v.airplayserver) 7e7c 00004bc7 ce156000
c0c61980 00000000 c008745c dc2d0e38 00004bc7 ce1f1af8
[83321.795994] c0 2084 (v.airplayserver) 7e9c a0060013 00000000
0000c350 00000000 1e848000 00000000 ce157f20 00000001
[83321.796018] c0 2084 (v.airplayserver) 7ebc 0000c350 00000000
1e848000 00000000 ce157f20 00000001 ce156000 c0db183c
[83321.796039] c0 2084 (v.airplayserver) 7edc c08870e8 0000c350
00000001 00000000 1e854350 00000000 00000001 00000000
[83321.796061] c0 2084 (v.airplayserver) 7efc ce156000 0000c350
00000000 ce157f98 c0087b44 0000c350 00000000 1e854350
[83321.796082] c0 2084 (v.airplayserver) 7f1c 00000000 cc6c5f20
00000000 00000000 00000000 fab25188 00004bc7 fab18e38
[83321.796104] c0 2084 (v.airplayserver) 7f3c 00004bc7 c0086618
c54449b8 00000001 00000824 c008745c 69612e76 616c7072
[83321.796108] c0 2084 (v.airplayserver)
R2: 0xc5447878:
[83321.796129] c0 2084 (v.airplayserver) 7878 c5447878 c5447878
c5447880 c5447880 c5447888 c5447888 c5447890 c5447890
[83321.796150] c0 2084 (v.airplayserver) 7898 c5447898 c5447898
c54478a0 c54478a0 c54478a8 c54478a8 c54478b0 c54478b0
[83321.796171] c0 2084 (v.airplayserver) 78b8 c54478b8 c54478b8
c54478c0 c54478c0 c54478c8 c54478c8 c54478d0 c54478d0
[83321.796194] c0 2084 (v.airplayserver) 78d8 c54478d8 c54478d8
00000000 00000064 00000064 00000000 00000000 00000000
[83321.796216] c0 2084 (v.airplayserver) 78f8 c54478f8 c54478f8
00000000 00000000 000136df 00000000 389fd980 00000000
[83321.796237] c0 2084 (v.airplayserver) 7918 dac4dac4 00000000
c54474c0 c544793c 00200200 c0db0210 ed3192cc c54475a4
[83321.796258] c0 2084 (v.airplayserver) 7938 04f2cf8e c544793c
c544793c ffffd918 ce1f1ac0 c0ca4800 ee0b1ac0 04f2d06d
[83321.796283] c0 2084 (v.airplayserver) 7958 00000000 00000000
de023377 00004bc7 de023377 00004bc7 00000000 d98e3c00

[83321.796286] c0 2084 (v.airplayserver)
R3: 0xc0097214:
[83321.796306] c0 2084 (v.airplayserver) 7214 1affffb9 e595317c
e3530005 0affffb6 e3550000 0affffb4 e5953124 e5835038
[83321.796327] c0 2084 (v.airplayserver) 7234 e5955120 e3550000
1afffffa eaffffae e1a00004 e58d1004 e3a07001 ebfffa6d
[83321.796350] c0 2084 (v.airplayserver) 7254 e59d1004 eaffff9b
e1a02005 eaffffaf e1a03004 eaffffb5 e1a00004 ebfffa65
[83321.796371] c0 2084 (v.airplayserver) 7274 eaffffd7 e59131b4
e3530005 1affffd4 eaffff9d e7f001f2 c0d01f74 c0c9b4b4
[83321.796395] c0 2084 (v.airplayserver) 7294 e92d40f8 e52de004
e8bd4000 e1a07000 e5905060 e2804058 e3550000 0a000036
[83321.796415] c0 2084 (v.airplayserver) 72b4 e594602c e594503c
e3560000 12466008 e1550006 11a05006 0a000031 e5940038
[83321.796435] c0 2084 (v.airplayserver) 72d4 e3500000 0a000003
e1a01006 ebffff42 e3500000 d5945038 e5940034 e3500000
[83321.796458] c0 2084 (v.airplayserver) 72f4 0a000003 e1a01006
ebffff3b e3500000 d5945034 e1a00004 e1a01005 ebfffebf
[83321.796462] c0 2084 (v.airplayserver)
R4: 0xc5447498:
[83321.796485] c0 2084 (v.airplayserver) 7498 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000
[83321.796506] c0 2084 (v.airplayserver) 74b8 00000000 00000000
57355734 00000000 00000000 00000000 00000003 00000021
[83321.796526] c0 2084 (v.airplayserver) 74d8 00000048 04f2cfc4
00000000 00000000 00000001 00000000 de021c07 00004bc7
[83321.796549] c0 2084 (v.airplayserver) 74f8 cc985000 00c0da6a
29275d16 0000034b 00000000 0315a8b6 115530e2 00000000
[83321.796571] c0 2084 (v.airplayserver) 7518 0000034b 00000000
00000001 00000001 2993334b 00000f7c 267b8ab8 000071c3
[83321.796595] c0 2084 (v.airplayserver) 7538 267b8ab8 000071c3
00000000 00000000 00000000 00000000 00000000 00000000
[83321.796615] c0 2084 (v.airplayserver) 7558 0000e090 00000000
00000000 00000000 00000037 00000000 04bc7de1 00000000
[83321.796636] c0 2084 (v.airplayserver) 7578 00000000 00000000
04bc7de0 00000000 0000001e 00000000 00000037 00000000
[83321.796641] c0 2084 (v.airplayserver)
R7: 0xc5447440:
[83321.796661] c0 2084 (v.airplayserver) 7440 00000000 ee0be5f0
ee0be5f0 00000000 00000001 00000000 00000000 00000000
[83321.796683] c0 2084 (v.airplayserver) 7460 ee0a2980 00000000
00000000 00000001 00000000 00000000 00000000 00000000
[83321.796708] c0 2084 (v.airplayserver) 7480 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000
[83321.796729] c0 2084 (v.airplayserver) 74a0 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000
[83321.796751] c0 2084 (v.airplayserver) 74c0 57355734 00000000
00000000 00000000 00000003 00000021 00000048 04f2cfc4
[83321.796774] c0 2084 (v.airplayserver) 74e0 00000000 00000000
00000001 00000000 de021c07 00004bc7 cc985000 00c0da6a
[83321.796796] c0 2084 (v.airplayserver) 7500 29275d16 0000034b
00000000 0315a8b6 115530e2 00000000 0000034b 00000000
[83321.796816] c0 2084 (v.airplayserver) 7520 00000001 00000001
2993334b 00000f7c 267b8ab8 000071c3 267b8ab8 000071c3
[83321.796820] c0 2084 (v.airplayserver)
R8: 0xce157ea0:
[83321.796841] c0 2084 (v.airplayserver) 7ea0 00000000 0000c350
00000000 1e848000 00000000 ce157f20 00000001 0000c350
[83321.796862] c0 2084 (v.airplayserver) 7ec0 00000000 1e848000
00000000 ce157f20 00000001 ce156000 c0db183c c08870e8
[83321.796882] c0 2084 (v.airplayserver) 7ee0 0000c350 00000001
00000000 1e854350 00000000 00000001 00000000 ce156000
[83321.796905] c0 2084 (v.airplayserver) 7f00 0000c350 00000000
ce157f98 c0087b44 0000c350 00000000 1e854350 00000000
[83321.796927] c0 2084 (v.airplayserver) 7f20 cc6c5f20 00000000
00000000 00000000 fab25188 00004bc7 fab18e38 00004bc7
[83321.796948] c0 2084 (v.airplayserver) 7f40 c0086618 c54449b8
00000001 00000824 c008745c 69612e76 616c7072 72657379
[83321.796971] c0 2084 (v.airplayserver) 7f60 00726576 00000000
ce1f1ac0 ce156000 047e3000 00000000 00000150 1dcd64ff
[83321.796992] c0 2084 (v.airplayserver) 7f80 000000a2 c000f124
ce156000 00000000 77d80ca4 c0087c60 00000000 1e848000
[83321.796994] c0 2084 (v.airplayserver)
R9: 0xc0c64440:
[83321.797018] c0 2084 (v.airplayserver) 4440 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797038] c0 2084 (v.airplayserver) 4460 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797062] c0 2084 (v.airplayserver) 4480 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797084] c0 2084 (v.airplayserver) 44a0 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797108] c0 2084 (v.airplayserver) 44c0 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797128] c0 2084 (v.airplayserver) 44e0 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797150] c0 2084 (v.airplayserver) 4500 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797173] c0 2084 (v.airplayserver) 4520 e7fddef0 e7fddef0
e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0 e7fddef0
[83321.797178] c0 2084 (v.airplayserver)
R10: 0xc5447440:
[83321.797200] c0 2084 (v.airplayserver) 7440 00000000 ee0be5f0
ee0be5f0 00000000 00000001 00000000 00000000 00000000
[83321.797221] c0 2084 (v.airplayserver) 7460 ee0a2980 00000000
00000000 00000001 00000000 00000000 00000000 00000000
[83321.797243] c0 2084 (v.airplayserver) 7480 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000
[83321.797265] c0 2084 (v.airplayserver) 74a0 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000
[83321.797286] c0 2084 (v.airplayserver) 74c0 57355734 00000000
00000000 00000000 00000003 00000021 00000048 04f2cfc4
[83321.797310] c0 2084 (v.airplayserver) 74e0 00000000 00000000
00000001 00000000 de021c07 00004bc7 cc985000 00c0da6a
[83321.797333] c0 2084 (v.airplayserver) 7500 29275d16 0000034b
00000000 0315a8b6 115530e2 00000000 0000034b 00000000
[83321.797354] c0 2084 (v.airplayserver) 7520 00000001 00000001
2993334b 00000f7c 267b8ab8 000071c3 267b8ab8 000071c3
[83321.797360] c0 2084 (v.airplayserver) Process v.airplayserver (pid:
2084, stack limit = 0xce156238)
[83321.797365] c0 2084 (v.airplayserver) Stack: (0xce157e18 to 0xce158000)
[83321.797370] c0 2084 (v.airplayserver) 7e00: c0097294 ce1f1d94
[83321.797375] c0 2084 (v.airplayserver) 7e20: c089595c ce156000
ce1f1ac0 c08880d4 ce157e90 fab25188 00004bc7 ce157f20
[83321.797380] c0 2084 (v.airplayserver) 7e40: ce156000 ce157f20
c54449b8 00000000 c08870e8 c0c644c0 c0c644c0 c0c644c0
[83321.797385] c0 2084 (v.airplayserver) 7e60: c0c644c0 c0c644c0
00000000 c0087120 c0c61980 00000000 fab18e38 00004bc7
[83321.797390] c0 2084 (v.airplayserver) 7e80: ce156000 c0c61980
00000000 c008745c dc2d0e38 00004bc7 ce1f1af8 a0060013
[83321.797395] c0 2084 (v.airplayserver) 7ea0: 00000000 0000c350
00000000 1e848000 00000000 ce157f20 00000001 0000c350
[83321.797399] c0 2084 (v.airplayserver) 7ec0: 00000000 1e848000
00000000 ce157f20 00000001 ce156000 c0db183c c08870e8
[83321.797403] c0 2084 (v.airplayserver) 7ee0: 0000c350 00000001
00000000 1e854350 00000000 00000001 00000000 ce156000
[83321.797408] c0 2084 (v.airplayserver) 7f00: 0000c350 00000000
ce157f98 c0087b44 0000c350 00000000 1e854350 00000000
[83321.797412] c0 2084 (v.airplayserver) 7f20: cc6c5f20 00000000
00000000 00000000 fab25188 00004bc7 fab18e38 00004bc7
[83321.797417] c0 2084 (v.airplayserver) 7f40: c0086618 c54449b8
00000001 00000824 c008745c 69612e76 616c7072 72657379
[83321.797421] c0 2084 (v.airplayserver) 7f60: 00726576 00000000
ce1f1ac0 ce156000 047e3000 00000000 00000150 1dcd64ff
[83321.797426] c0 2084 (v.airplayserver) 7f80: 000000a2 c000f124
ce156000 00000000 77d80ca4 c0087c60 00000000 1e848000
[83321.797431] c0 2084 (v.airplayserver) 7fa0: 437b1bac c000ef80
437b1bac 00000150 77d80c70 00000000 00000001 00000128
[83321.797436] c0 2084 (v.airplayserver) 7fc0: 437b1bac 00000150
1dcd64ff 000000a2 77544008 1e848000 437b1ba8 77d80ca4
[83321.797441] c0 2084 (v.airplayserver) 7fe0: 0000002a 77d80c68
4157025c 4009fe44 20060010 77d80c70 ff080001 ff080001
[83321.797457] c0 2084 (v.airplayserver) [<c02c22f0>]
(rb_next+0x0/0x60) from [<c00973a0>] (pick_next_task_fair+0x10c/0x138)
[83321.797478] c0 2084 (v.airplayserver) [<c00973a0>]
(pick_next_task_fair+0x10c/0x138) from [<c08880d4>]
(__schedule+0x678/0x7e8)
[83321.797491] c0 2084 (v.airplayserver) [<c08880d4>]
(__schedule+0x678/0x7e8) from [<c08870e8>] (do_nanosleep+0xb4/0x134)
[83321.797502] c0 2084 (v.airplayserver) [<c08870e8>]
(do_nanosleep+0xb4/0x134) from [<c0087b44>]
(hrtimer_nanosleep+0x98/0x110)
[83321.797509] c0 2084 (v.airplayserver) [<c0087b44>]
(hrtimer_nanosleep+0x98/0x110) from [<c0087c60>]
(SyS_nanosleep+0xa4/0xb0)
[83321.797523] c0 2084 (v.airplayserver) [<c0087c60>]
(SyS_nanosleep+0xa4/0xb0) from [<c000ef80>]
(ret_fast_syscall+0x0/0x30)
[83321.797531] c0 2084 (v.airplayserver) Code: 15821000 e8900007
e8830007 e12fff1e (e5902000)
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