Re: [PATCH v2] ftrace: Hide a extra entry in stack trace

[Tatsuya S <tatsuya.s2862@gmail.com>]

On 10/1/24 10:47 PM, Steven Rostedt wrote:
> On Tue, 1 Oct 2024 22:27:03 +0900
> ts <tatsuya.s2862@gmail.com> wrote:
> 
>>> ...
>>>                 sh-140     [001] ...1.    18.352601: myevent: (vfs_write+0x4/0x560)
>>>                 sh-140     [001] ...1.    18.352602: <stack trace>
>>>    => ksys_write
>>>    => do_syscall_64
>>>    => entry_SYSCALL_64_after_hwframe
>>>                 sh-140     [001] ...1.    18.352602: vfs_write <-ksys_write
>>>                 sh-140     [001] ...1.    18.352604: <stack trace>
>>>    => ftrace_regs_call
>>>    => vfs_write
>>>    => ksys_write
>>>    => do_syscall_64
>>>    => entry_SYSCALL_64_after_hwframe
>>> ------
>>> As you can see, myevent skips "vfs_write".
>>> (and function tracer still have ftrace_regs_call() )
>>
>> Thanks for the other tests. This issue may be function_trace_call()
>> specific problem.
>>
>> So I will change the place to increment skip number.
> 
> My fear is that we are going to just break it elsewhere. The problem with
> the "skip" is that there's so many configurations when we get here, we may
> not really know what to skip. If the compiler inlines something, then we
> may skip something we do not want to.
> 
> I rather have extra information than not enough.
> 
> -- Steve

It may not be clean and be bit redundant, but I think it would be more 
maintainable to treat

"skip(and skipped functions)" separately only at the top(parent) of 
functions that display stack trace.


thanks.