2.6.31-rc5-git2 crash on a idle system.

[Sachin Sant]

I have a power6 blade [IBM,7998-61X] running 2.6.31-rc5-git2
kernel (a33a052f19a21d727847391c8c1aff3fb221c472). After some
period of inactivity the machine drops into xmon with following
traces.

 cpu 0x0: Vector: 700 (Program Check) at [c00000000ffffa90]
    pc: c000000000600000: .flow_cache_new_hashrnd+0x3c/0xcc
    lr: c0000000000c6038: .run_timer_softirq+0x20c/0x2f4
    sp: c00000000ffffd10
   msr: 8000000000089032
  current = 0xc000000000f58b70
  paca    = 0xc0000000010b2400
    pid   = 0, comm = swapper
enter ? for help
[c00000000ffffda0] c0000000000c6038 .run_timer_softirq+0x20c/0x2f4
[c00000000ffffea0] c0000000000be8a0 .__do_softirq+0x174/0x2c8
[c00000000fffff90] c0000000000307b0 .call_do_softirq+0x14/0x24
[c000000001013870] c00000000000ecf8 .do_softirq+0xa0/0x104
[c000000001013910] c0000000000be1d0 .irq_exit+0x74/0xd4
[c000000001013990] c00000000002ce20 .timer_interrupt+0x1cc/0x200
[c000000001013a30] c000000000003728 decrementer_common+0x128/0x180
--- Exception: 901 (Decrementer) at c00000000000ec3c .raw_local_irq_restore+0xc0/0xdc
[c000000001013dc0] c000000000015824 .cpu_idle+0x13c/0x1e0
[c000000001013e60] c000000000009fe8 .rest_init+0x94/0xcc
[c000000001013ee0] c000000000990cf4 .start_kernel+0x484/0x4a8
[c000000001013f90] c000000000008408 .start_here_common+0x2c/0xa4
0:mon> di $.flow_cache_new_hashrnd
c0000000005fffc4  7c0802a6      mflr    r0
c0000000005fffc8  f8010010      std     r0,16(r1)
c0000000005fffcc  fb81ffe0      std     r28,-32(r1)
c0000000005fffd0  fba1ffe8      std     r29,-24(r1)
c0000000005fffd4  fbc1fff0      std     r30,-16(r1)
c0000000005fffd8  fbe1fff8      std     r31,-8(r1)
c0000000005fffdc  f821ff71      stdu    r1,-144(r1)
c0000000005fffe0  7c3f0b78      mr      r31,r1
c0000000005fffe4  ebc2dc90      ld      r30,-9072(r2)
c0000000005fffe8  3b800001      li      r28,1
c0000000005fffec  60000000      nop
 ...
c0000000005ffff4  e93e8048      ld      r9,-32696(r30)
c0000000005ffff8  38a0ffff      li      r5,-1
c0000000005ffffc  eba90000      ld      r29,0(r9)
c000000000600000  00001010      .long 0x1010
0:mon> 
c000000000600004  00000008      .long 0x8
c000000000600008  00001013      .long 0x1013
c00000000060000c  0000000f      .long 0xf
c000000000600010  7961626f      rldimi. r1,r11,44,41
c000000000600014  6f740000      xoris   r20,r27,0
c000000000600018  00101600      .long 0x101600
c00000000060001c  00000c00      .long 0xc00
c000000000600020  00000400      .long 0x400
c000000000600024  00101100      .long 0x101100
c000000000600028  000008e9      .long 0x8e9
c00000000060002c  60000000      nop
c000000000600030  e93e8050      ld      r9,-32688(r30)
c000000000600034  7c6507b4      extsw   r5,r3
c000000000600038  78ab4da4      rldicr  r11,r5,9,54
c00000000060003c  396b0040      addi    r11,r11,64
c000000000600040  80090000      lwz     r0,0(r9)
0:mon> r
R00 = c0000000000c6038   R16 = 0000000000000000
R01 = c00000000ffffd10   R17 = 0000000000000100
R02 = c000000001011110   R18 = c000000001059300
R03 = 0000000000000000   R19 = c000000001102f98
R04 = c00000000ffffd60   R20 = c000000001103398
R05 = ffffffffffffffff   R21 = c000000001103798
R06 = 00000000000006d0   R22 = c000000001103b98
R07 = 0000000000000001   R23 = 0000000000000000
R08 = 0000000000830000   R24 = c00000000fffc000
R09 = c00000000072f890   R25 = 0000000000000000
R10 = c00000000120fbf8   R26 = 0000000000200200
R11 = c000000000600090   R27 = c00000000ffffe10
R12 = 0000000028000022   R28 = 0000000000000001
R13 = c0000000010b2400   R29 = c0000000010805e8
R14 = 0000000000382800   R30 = c000000000fb4f78
R15 = 0000000000000000   R31 = c00000000ffffd10
pc  = c000000000600000 .flow_cache_new_hashrnd+0x3c/0xcc
lr  = c0000000000c6038 .run_timer_softirq+0x20c/0x2f4
msr = 8000000000089032   cr  = 28000024
ctr = c0000000005fffc4   xer = 0000000000000000   trap =  700
0:xmon>

This is a 8 cpu system. Other cpu's are in idle state. Last
vanilla kernel that worked fine was 2.6.31-rc4-git2
(4733fd328f14280900435d9dbae1487d110a4d56).

dmesg log and .config attached.

Thanks
-Sachin



-- 

---------------------------------
Sachin Sant
IBM Linux Technology Center
India Systems and Technology Labs
Bangalore, India
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