Kernel crash caused by cpufreq

[Michael Ellerman]

On Fri, 2014-07-25 at 11:07 +1000, Gavin Shan wrote:
> I'm tracing one LSI interrupt issue on P8 box, and eventually into the
> following kernel crash. Not sure if there is one fix against this? :-)
 
Vaidy wrote that I'm pretty sure (on CC).

> Starting Linux PPC64 #401 SMP Fri Jul 25 10:52:28 EST 2014
> -----------------------------------------------------
> ppc64_pft_size                = 0x0
> physicalMemorySize            = 0x800000000
> htab_address                  = 0xc0000007fe000000
> htab_hash_mask                = 0x3ffff
> -----------------------------------------------------
>  <- setup_system()
> Initializing cgroup subsys cpuset
> Initializing cgroup subsys cpuacct
> Linux version 3.16.0-rc6-00076-g4226dbe-dirty (shangw at shangw) (gcc version 4.5.2 (crosstool-NG 1.19.0) ) #401 SMP Fri Jul 25 10:52:28 EST 2014
> 	:
> < Unrelated log stripped >

Are you sure there's nothing else in the log that might be related? See the
messages in init_powernv_pstates() for example.

> ------------[ cut here ]------------
> kernel BUG at drivers/cpufreq/powernv-cpufreq.c:134!
> cpu 0x1: Vector: 700 (Program Check) at [c0000007f8483370]
>     pc: c00000000096f32c: .pstate_id_to_freq+0x2c/0x50
>     lr: c00000000096f37c: .powernv_read_cpu_freq+0x2c/0x50
>     sp: c0000007f84835f0
>    msr: 9000000000029032
>   current = 0xc0000007f8400000
>   paca    = 0xc00000000ff00400	 softe: 0	 irq_happened: 0x01
>     pid   = 1, comm = swapper/0
> kernel BUG at drivers/cpufreq/powernv-cpufreq.c:134!
> enter ? for help
> [link register   ] c00000000096f37c .powernv_read_cpu_freq+0x2c/0x50
> [c0000007f84835f0] c000000001076070 key_type_dns_resolver+0xef20/0x40d20 (unreliable)
> [c0000007f8483670] c00000000010812c .generic_exec_single+0x8c/0x270
> [c0000007f8483730] c0000000001083d0 .smp_call_function_single+0x90/0xb0
> [c0000007f84837b0] c000000000108cec .smp_call_function_any+0x15c/0x200
> [c0000007f8483860] c00000000096f27c .powernv_cpufreq_get+0x3c/0x60
> [c0000007f84838f0] c000000000969dc4 .__cpufreq_add_dev.clone.11+0x574/0xa20
> [c0000007f84839e0] c0000000005f7a4c .subsys_interface_register+0xec/0x130
> [c0000007f8483a90] c000000000967af8 .cpufreq_register_driver+0x168/0x2d0
> [c0000007f8483b30] c000000000f774cc .powernv_cpufreq_init+0x210/0x244
> [c0000007f8483be0] c00000000000bc08 .do_one_initcall+0xc8/0x240
> [c0000007f8483ce0] c000000000f44054 .kernel_init_freeable+0x268/0x33c
> [c0000007f8483db0] c00000000000c4dc .kernel_init+0x1c/0x110
> [c0000007f8483e30] c00000000000a428 .ret_from_kernel_thread+0x58/0xb0
> 1:mon> e
> cpu 0x1: Vector: 700 (Program Check) at [c0000007f8483370]
>     pc: c00000000096f32c: .pstate_id_to_freq+0x2c/0x50
>     lr: c00000000096f37c: .powernv_read_cpu_freq+0x2c/0x50
>     sp: c0000007f84835f0
>    msr: 9000000000029032
>   current = 0xc0000007f8400000
>   paca    = 0xc00000000ff00400	 softe: 0	 irq_happened: 0x01
>     pid   = 1, comm = swapper/0
> kernel BUG at drivers/cpufreq/powernv-cpufreq.c:134!
> 1:mon> r
> R00 = 0000000000000042   R16 = 0000000000000000
> R01 = c0000007f84835f0   R17 = 0000000000000000
> R02 = c00000000116c430   R18 = 0000000000000000
> R03 = ffffffffffffffbe   R19 = 0000000000000001
> R04 = 0000000000000000   R20 = c00000078bd61e58
> R05 = c00000000114ca78   R21 = c000000001008910
> R06 = c0000007f84838d0   R22 = c0000000011c1b74
> R07 = 0000000000000001   R23 = c000000002200030
> R08 = c0000000011c1910   R24 = 0000000000000001
> R09 = c000000001f2970c   R25 = c000000001008730
> R10 = 0000000000000001   R26 = c000000001f29478
> R11 = 0000000000000042   R27 = c0000007f84838d0
> R12 = 0000000044002084   R28 = c00000000114ca78
> R13 = c00000000ff00400   R29 = 0000000000000000
> R14 = c00000000000c4c0   R30 = c0000000010a90f0
> R15 = 0000000000000000   R31 = c0000007f84838d0
> pc  = c00000000096f32c .pstate_id_to_freq+0x2c/0x50
> cfar= c00000000096f324 .pstate_id_to_freq+0x24/0x50
> lr  = c00000000096f37c .powernv_read_cpu_freq+0x2c/0x50
> msr = 9000000000029032   cr  = 44002082
> ctr = c00000000096f350   xer = 0000000020000000   trap =  700
> 1:mon>

Gavin, in future for a dump like this it's very helpful to see the actual code
that hit the bug. You can get that with:

1:mon> di $.pstate_id_to_freq


Vaidy, judging by r3 it looks like i became negative. That would obviously
happen if powernv_pstate_info.max was zero?

cheers