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Re: [PATCH v5 0/6] arm64: ftrace: fix incorrect output from stack tracer

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On Nov 10, 2015, at 11:58 AM, AKASHI Takahiro wrote:

Hi Akashi,

> On 11/09/2015 11:24 PM, Jungseok Lee wrote:
>> On Nov 6, 2015, at 3:44 PM, AKASHI Takahiro wrote:
>> 
>> Hi Akashi,
>> 
>>> This is the fifth patch series for fixing stack tracer on arm64.
>>> The original issue was reported by Jungseok[1], and then I found more
>>> issues[2].
>>> 
>>> We don't have to care about the original issue because the root cause
>>> (patch "ARM64: unwind: Fix PC calculation") has been reverted in v4.3.
>>> 
>>> I address here all the issues and implement fixes described in [2] except
>>> for interrupt-triggered problems(II-3) and leaf function(II-5).  Recent
>>> discussions[3] about introducing a dedicated interrupt stack suggests that
>>> we may avoid walking through from an interrupt stack to a process stack.
>>> (So interrupt-stack patch is a prerequisite.)
>>> 
>>> Basically,
>>> patch1 is a proactive improvement of function_graph tracer.
>>> patch2 corresponds to II-4(functions under function_graph tracer).
>>> patch3, 4 and 5 correspond to II-1(slurping stack) and II-2(differences
>>> between x86 and arm64).
>>> patch6 is a function prologue analyzer test. This won't attest
>>> the correctness of the functionality, but it can suggest that all
>>> the traced functions are treated properly by this function.
>>> (Please note that patch3 has already been queued in Steven's for-next.)
>>> 
>>> I tested the code with v4.3 + Jungseok's patch v5[4].
>> 
>> I've played this series with IRQ stack patch and it works well at least
>> on my system! In addition to this condition, I've run these changes without
>> IRQ stack since it is in progress. I could observe a single strange behavior,
>> minus stack size around elX_irq. Am I missing something?
> 
> You saw the result like:
> ...
> 13)     4336      64   gic_handle_irq+0x5c/0xa4
> 14)     4272     576   el1_irq+0x68/0xd8
> 15)     3696    -160   smc_hardware_send_pkt+0x278/0x42c
> 
> This is the most difficult problem that I mentioned in II-3 of [1] and tried to fix.
> For example, smc_hardware_send_pkt is NOT the function interrupted, but
> _raw_spin_unlock_irqstore which is called at '+0x278/0x42c' is.
> Giving a *perfect* solution against it is quite tough (and complicated).
> Since you have introduced interrupt stack and even on x86 an interrupt stack is
> not supported, I removed related patches.

Yes, that is what I've observed. I was not sure whether the behavior is related to
II-3, interrupted frame, or not. Thanks for clarification!

Best Regards
Jungseok Lee--
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[PATCH v5 0/6] arm64: ftrace: fix incorrect output from stack tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
  [PATCH v5 5/6] arm64: ftrace: add arch-specific stack tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
    Re: [PATCH v5 5/6] arm64: ftrace: add arch-specific stack tracer Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-10 15:10 +0100
      Re: [PATCH v5 5/6] arm64: ftrace: add arch-specific stack tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-11 06:10 +0100
        Re: [PATCH v5 5/6] arm64: ftrace: add arch-specific stack tracer Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-12 00:00 +0100
  [PATCH v5 4/6] arm64: insn: add instruction decoders for ldp/stp and add/sub AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
    Re: [PATCH v5 4/6] arm64: insn: add instruction decoders for ldp/stp and add/sub Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-10 14:50 +0100
      Re: [PATCH v5 4/6] arm64: insn: add instruction decoders for ldp/stp  and add/sub AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-11 06:00 +0100
  [PATCH v5 1/6] arm64: ftrace: modify a stack frame in a safe way AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
  [PATCH v5 2/6] arm64: ftrace: fix a stack tracer's output under function graph tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
    Re: [PATCH v5 2/6] arm64: ftrace: fix a stack tracer's output under function graph tracer Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-09 15:10 +0100
      Re: [PATCH v5 2/6] arm64: ftrace: fix a stack tracer's output under  function graph tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-10 03:50 +0100
        Re: [PATCH v5 2/6] arm64: ftrace: fix a stack tracer's output under function graph tracer Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-13 16:10 +0100
          Re: [PATCH v5 2/6] arm64: ftrace: fix a stack tracer's output under  function graph tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-16 10:30 +0100
  [PATCH v5 3/6] ftrace: allow arch-specific stack tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
    Re: [PATCH v5 3/6] ftrace: allow arch-specific stack tracer Steven Rostedt <rostedt@goodmis.org> - 2015-11-06 14:40 +0100
  [PATCH v5 6/6] arm64: ftrace: add a test of function prologue analyzer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-06 07:50 +0100
  Re: [PATCH v5 0/6] arm64: ftrace: fix incorrect output from stack tracer Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-09 15:30 +0100
    Re: [PATCH v5 0/6] arm64: ftrace: fix incorrect output from stack  tracer AKASHI Takahiro <takahiro.akashi@linaro.org> - 2015-11-10 04:00 +0100
      Re: [PATCH v5 0/6] arm64: ftrace: fix incorrect output from stack tracer Jungseok Lee <jungseoklee85@gmail.com> - 2015-11-10 14:40 +0100

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