linux-kernel - Re: [RFC PATCH] ftrace: Fix depth filtering when func

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Date:   Tue, 23 Jan 2018 08:58:06 +0200
From:   Nikolay Borisov <nborisov@...e.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ftrace: Fix depth filtering when func_stack is
 enabled.



On 23.01.2018 01:16, Steven Rostedt wrote:
> On Mon, 22 Jan 2018 15:50:04 +0200
> Nikolay Borisov <nborisov@...e.com> wrote:
> 
> 
>> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
>> index 27f7ad12c4b1..b721f1f3f3c0 100644
>> --- a/kernel/trace/trace_functions.c
>> +++ b/kernel/trace/trace_functions.c
>> @@ -181,14 +181,11 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
>>  		pc = preempt_count();
>>  		trace_function(tr, ip, parent_ip, flags, pc);
>>  		/*
>> -		 * skip over 5 funcs:
>> -		 *    __ftrace_trace_stack,
>> -		 *    __trace_stack,
>> +		 * skip over 2 funcs:
>>  		 *    function_stack_trace_call
>> -		 *    ftrace_list_func
> 
> Thanks, but this breaks when you are not using ORC unwinder.

Actually I've tested this with the frame_pointer unwinder, I haven't got
ORC to work at all. So this patch fixes the issue where the FP unwinder
prints out shorter stacktraces than required.

> 
>>  		 *    ftrace_call
>>  		 */
>> -		__trace_stack(tr, flags, 5, pc);
>> +		__trace_stack(tr, flags, 2, pc);
>>  	}
>>  
>>  	atomic_dec(&data->disabled);
> 
> 
> There's a bit of ORC unwinder breakage that I'm still dealing with. I
> also have patches to handle the differences between ORC and FP, in the
> __trace_stack() usages. I'm hoping to have this all fixed by tomorrow,
> as I'll be traveling after that.

Great, please CC me on the patches so that I can test them.

> 
> Thanks!
> 
> -- Steve
> 
>