[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4AF05E0C.5090305@monstr.eu>
Date: Tue, 03 Nov 2009 17:45:00 +0100
From: Michal Simek <monstr@...str.eu>
To: Steven Rostedt <srostedt@...hat.com>
CC: mingo@...e.hu, linux-kernel@...r.kernel.org,
John Williams <john.williams@...alogix.com>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Ftrace for Microblaze - notrace
Steven Rostedt wrote:
> On Tue, 2009-11-03 at 14:32 +0100, Michal Simek wrote:
>> Hi Thomas, Ingo, Steven and others
>>
>> I am working on ftrace support for Microblaze. I have done basic ftrace
>> support - initcall, kmemtrace and other.
>> Currently I am working on function trace support. I did asm code as is
>> written in Documentation/trace/ftrace-design.txt.
>>
>> I have two poins/questions.
>>
>> I desided to use HAVE_FUNCTION_TRACE_MCOUNT_TEST - just test
>> function_trace_stop in asm code - that shouldn't be a problem.
>
> Yeah, and if you don't have that, it is taken care of in the generic
> code too.
jj, I know - asm checking is just two instruction - that's why I use it.
>
>> I disable -pg in main Makefile because not work for me (more info below)
>> and I enable it just for two file in arch/microblaze (irq.c and intc.c)
>> - recompile kernel and test. Log is below and you can see that I am able
>> to see output for function. That's why I think that my mcount function
>> should be correct. Am I right?
>>
>> uclinux login: root
>> Password:
>> # cd ; mkdir /debug; mount -t debugfs none /debug; cat
>> /debug/tracing/available_
>> tracers; echo function > /debug/tracing/current_tracer;echo 1 >
>> /debug/tracing/t
>> racing_enabled;cat /debug/tracing/trace | head -n 10
>> wakeup_rt wakeup function sched_switch nop
>> # tracer: function
>> #
>> # TASK-PID CPU# TIMESTAMP FUNCTION
>> # | | | | |
>> sh-52 [000] 184.940000: irq_call <-do_IRQ
>> sh-52 [000] 184.940000: do_IRQ <-get_irq
>> sh-52 [000] 184.940000: handle_level_irq <-intc_mask_ack
>> sh-52 [000] 184.950000: handle_level_irq
>> <-intc_enable_or_unmask
>> sh-52 [000] 184.950000: do_IRQ <-get_irq
>> sh-52 [000] 184.950000: handle_level_irq <-intc_mask_ack
>> #
>>
>>
>> When is used -pg flag kernel stops when I enable function tracer.
>> Interesting is that freeze than I setup function tracing (echo function
>> > .../current/tracer). Is it correct behavior? I think that trace
>> should start after (echo 1> .../tracing_enabled).
>
> No, tracing_enabled is default on and should not be used (may go away).
> Tracing starts as soon as you echo function into current_tracer.
ok
>
>>
>> The next thing is about annotation notrace. I look at all arch. Is there
>> any algorithm which function should use it? I think that this could be a
>> reason why I my kernel freeze when enable function tracer.
>>
>> I tested to add -pg flag for process.c file and after it kernel freeze
>> too. Is it mean that problem could be there?
>
> Probably.
Is there any manual or instruction which functions are dangerous and
especially why?
>
>> Any other suggestion?
>
> Just remember that -pg is very intrusive. I don't know your arch, nor
> have I seen the code you did to update it. You can disable the -pg from
> process.c by adding in the Makefile:
>
> CFLAGS_REMOVE_process.o = -pg
jj, I know how to do it.
>
> And that will keep the process.c from being compiled with it. There may
> be other files in the arch that should not have it. There's several in
> x86 and in PowerPC.
Do you know why they exclude it?
Can I use any special debug features? I mean I look at kernel.h and
there are some trace_printk function - but they don't work for me. Is it
possible to use them or not?
Thanks,
Michal
>
> -- Steve
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists