arm64 function_graph tracer panic with CONFIG_DYNAMIC_FTRACE

Fri Nov 13 07:16:53 PST 2015

On Nov 13, 2015, at 2:51 PM, AKASHI Takahiro wrote:

Hi Akashi and Catalin,

> Catalin,
> (add lakml back to Cc)
> 
> On 11/13/2015 01:01 AM, Catalin Marinas wrote:
> > On Fri, Nov 13, 2015 at 12:00:42AM +0900, AKASHI Takahiro wrote:
> >> If possible, please try again with "select HAVE_FUNCTION_GRAPH_FP_TEST" added
> >> to CONFIG_ARM64.
> >> It will insert an additional check. I hope this will help.
> >
> > So it looks the the frame is off by some amount:
> 
> I was able to reproduce the problem on hikey, too.

Hmm, I don't find a 100% reproduction step yet.

> > # echo function_graph > /sys/kernel/debug/tracing/current_tracer
> > Bad frame pointer: expected ffffffc976b3bd50, received ffffffc976b3be60
> 
> The difference of fp's was 0x110(sizeof(pt_reg_t)=0x120).
> It seems that an interrupt happened here (and we might have unwound one extra frame?).

Am I the only person to observe the following log?

 NOHZ: local_softirq_pending 20

The log comes from line760 of kernel/time/tick-sched.c.

I will update if I figure out something useful.

Best Regards
Jungseok Lee

> >    from func psci_cpu_suspend return to ffffffc00008d058
> 
> Always in the same place.
> 
> > ------------[ cut here ]------------
> > WARNING: at /work/Linux/linux-2.6-aarch64/kernel/trace/trace_functions_graph.c:223
> > Modules linked in:
> >
> > CPU: 4 PID: 0 Comm: swapper/4 Not tainted 4.3.0+ #584
> > Hardware name: Juno (DT)
> > task: ffffffc976b22f00 ti: ffffffc976b38000 task.ti: ffffffc976b38000
> > PC is at ftrace_return_to_handler+0x11c/0x150
> > LR is at ftrace_return_to_handler+0x11c/0x150
> > pc : [<ffffffc000172034>] lr : [<ffffffc000172034>] pstate: 800001c5
> > sp : ffffffc976b3bdd0
> > x29: ffffffc976b3bdd0 x28: ffffffc0006c9000
> > x27: ffffffc000a29f20 x26: ffffffc976b3bf70
> > x25: 000000cc2c13e054 x24: 0000000000000004
> > x23: ffffffc000aeb790 x22: 0000000000000002
> > x21: ffffffc975503200 x20: ffffffc000aeb850
> > x19: 0000000000000002 x18: ffffffc000b3a920
> > x17: 0000000000000000 x16: 0000000000000000
> > x15: ffffffc000b3a5bf x14: 3739636666666666
> > x13: 6620646576696563 x12: 6572202c30356462
> > x11: 3362363739636666 x10: 00000000000000fc
> > x9 : ffffffc9768070c0 x8 : 0000000000001dd0
> > x7 : ffffffc9760f4c80 x6 : ffffffc9760f4c00
> > x5 : 00000000000084c0 x4 : 0000000000000001
> > x3 : ffffffc976b3bc50 x2 : 0000000000000001
> > x1 : 000000000000007f x0 : 000000000000007f
> >
> > ---[ end trace ac97c44ba7dabcce ]---
> > Call trace:
> > [<ffffffc000172034>] ftrace_return_to_handler+0x11c/0x150
> > [<ffffffc0000924bc>] return_to_handler+0x1c/0x40
> > [<ffffffc0000924a0>] return_to_handler+0x0/0x40
> > [<ffffffc0000924a0>] return_to_handler+0x0/0x40
> > [<ffffffc0000924a0>] return_to_handler+0x0/0x40
> > [<ffffffc0000924a0>] return_to_handler+0x0/0x40
> > [<ffffffc0000924a0>] return_to_handler+0x0/0x40
> > [<ffffffc0000924a0>] return_to_handler+0x0/0x40
> 
> These call stacks were:
>  (psci_cpu_suspend)
>  psci_suspend_finisher
>  (cpu_suspend_enter?)
>  cpu_suspend
>  cpu_psci_cpu_suspend
>  arm_cpuidle_suspend
>  arm_enter_idle_state
>  cpuidle_enter_state
>  cpuidle_enter
>  call_cpuidle
>  (cpu_startup_entry?)
> 
> and if cpuidle is turned off(cpuidle.off=1), the panic never happens.
> That is all what I know at this moment.
> 
> -Takahiro AKASHI
> 
> 
> > [<ffffffc000090208>] secondary_start_kernel+0x130/0x158
> > Unable to handle kernel NULL pointer dereference at virtual address 00000000
> > pgd = ffffffc000b68000
> > [00000000] *pgd=00000009f69ea003, *pud=00000009f69ea003, *pmd=00000009f69eb003, *pte=006000002c010707
> > Internal error: Oops: 96000006 [#1] PREEMPT SMP
>  [snip]
> 
> 
> On 11/12/2015 07:42 PM, Catalin Marinas wrote:
>> Hi Takahiro,
>> 
>> I was trying to assess what's working/not working in ftrace on arm64 and
>> whether your recent patches are meant for 4.4 or can wait until 4.5.
>> However, without any patches applied on a 4.3 kernel, enabling the
>> function_graph tracer when CONFIG_DYNAMIC_FTRACE is enabled panics the
>> kernel. Strangely, it does not happen if only a single CPU is on.
>> However, with function_graph tracer on, onlining a second CPU leads to a
>> similar panic.
>> 
>> Below is the kernel panic with 2 CPUs online on a Juno board. There
>> isn't much stack trace information for CPU 5 where the fault happened,
>> the frame pointer (x29) seems corrupted as well. Any idea? Thanks.
>> 
>> # echo function_graph > /sys/kernel/debug/tracing/current_tracer
>> swapper/5[0]: undefined instruction: pc=ffffffc000a46698
>> Code: 0009ccf8 ffffffc0 00000000 00000000 (00000030)
>> Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP
>> Modules linked in:
>> CPU: 5 PID: 0 Comm: swapper/5 Not tainted 4.3.0 #574
>> Hardware name: Juno (DT)
>> task: ffffffc976b23ac0 ti: ffffffc976b3c000 task.ti: ffffffc976b3c000
>> PC is at cpu_online_bits+0x0/0x8
>> LR is at cpu_online_bits+0x0/0x8
>> pc : [<ffffffc000a46698>] lr : [<ffffffc000a46698>] pstate: 600001c5
>> sp : ffffffc976b3ff40
>> x29: 0000000000000002 x28: ffffffc000100c0c
>> x27: ffffffc000aeb790 x26: ffffffc9758d5800
>> x25: 0000000000000002 x24: ffffffc0000924a0
>> x23: ffffffc976b3ff40 x22: ffffffc00056841c
>> x21: ffffffc000a25b80 x20: ffffffc000aeb790
>> x19: ffffffc9758d5800 x18: 0000000000000000
>> x17: 0000000000000000 x16: 0000000000000000
>> x15: 0000000000000000 x14: 0000000000000000
>> x13: 0000000000000000 x12: 0000000034d5d91d
>> x11: 0000000000000000 x10: 0000000000001000
>> x9 : ffffffc9768070c0 x8 : 00000000000007d8
>> x7 : 0000001b280eb7c4 x6 : 0000000000000015
>> x5 : 000000000000000a x4 : ffffffc0792a4990
>> x3 : ffffffffffffffa1 x2 : ffffffc0792a4800
>> x1 : ffffffc0000949e0 x0 : ffffffffffffffa1
>> 
>> Process swapper/5 (pid: 0, stack limit = 0xffffffc976b3c020)
>> Stack: (0xffffffc976b3ff40 to 0xffffffc976b40000)
>> ff40: ffffffc976b3ff70 ffffffc0000924a0 ffffffc976b3c000 ffffffc000a46000
>> ff60: ffffffc000b20000 0000001b27d716c0 ffffffc976b3ffd0 ffffffc000090208
>> ff80: 0000000000000005 0000000000000e12 ffffffc000b306a0 0000000000000000
>> ffa0: 0000000000000000 0000000000000000 0000000080b65000 0000000080b68000
>> ffc0: ffffffc0000827f0 0000000000000000 0000000000000000 00000000800827dc
>> ffe0: 0000000000000000 0000000000000000 068824085611a721 280b8a0b05808446
>> Call trace:
>> Code: 0009ccf8 ffffffc0 00000000 00000000 (00000030)
>> ---[ end trace 702bb2ed35464601 ]---
>> Kernel panic - not syncing: Attempted to kill the idle task!
>> CPU4: stopping
>> CPU: 4 PID: 0 Comm: swapper/4 Tainted: G      D         4.3.0 #574
>> Hardware name: Juno (DT)
>> Call trace:
>> [<ffffffc00008aaa8>] dump_backtrace+0x0/0x150
>> [<ffffffc00008ac1c>] show_stack+0x24/0x30
>> [<ffffffc0003b21a0>] dump_stack+0x90/0xd0
>> [<ffffffc000090880>] handle_IPI+0x280/0x290
>> [<ffffffc00008255c>] gic_handle_irq+0x94/0xb0
>> Exception stack(0xffffffc976b3bd70 to 0xffffffc976b3be90)
>> bd60:                                   0000001b2ed1ee8c ffffffc000aeb850
>> bd80: ffffffc976b3bec0 ffffffc0005681dc 0000000080000145 ffffffc00009244c
>> bda0: 0000000000000000 0000000000000001 ffffffc976b38000 0000000000000003
>> bdc0: ffffffc976b38000 ffffffc000a282a8 ffffffc976b38000 ffffffc0000ecb28
>> bde0: 00000000000006ed ffffffc9768070c0 00000000000007e0 ffffffc0006d04a8
>> be00: 0000000000000001 0000000000005a0e 0000000000000001 ffffffc0006d04a8
>> be20: 0000000000000000 0000000000000000 0000000000000001 0000001b2ed1ee8c
>> be40: ffffffc000aeb850 ffffffc9758d5600 0000000000000000 ffffffc000aeb790
>> be60: 0000000000000004 0000001b2e40a7ec ffffffc976b3bf70 ffffffc000a29f20
>> be80: ffffffc0006c9000 ffffffc976b3bec0
>> [<ffffffc0000855ac>] el1_irq+0x6c/0xe0
>> [<ffffffc00056842c>] cpuidle_enter+0x34/0x48
>> [<ffffffc000100c30>] call_cpuidle+0x48/0x80
>> [<ffffffc000100e90>] cpu_startup_entry+0x228/0x308
>> [<ffffffc000090208>] secondary_start_kernel+0x130/0x158
>> ---[ end Kernel panic - not syncing: Attempted to kill the idle task!
>> 