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

Hi Akashi,

On 11/09/2015 11:24 PM, Jungseok Lee wrote:

quoted

On Nov 6, 2015, at 3:44 PM, AKASHI Takahiro wrote:

Hi Akashi,

quoted

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