linux-kernel - dynamic ftrace

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Date:	Mon, 09 Nov 2009 17:52:16 +0100
From:	Michal Simek <monstr@...str.eu>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	wuzhangjin@...il.com, linux-kernel@...r.kernel.org,
	John Williams <john.williams@...alogix.com>
Subject: dynamic ftrace - graph

Hi Steve and others,

I have working dynamic ftrace function. :-)

I look at __ftrace_modify_code function and I have one question about.
Below are function which are called when I enable function_graph.

I personally think that make more sense to call 
ftrace_enable_ftrace_graph_caller before ftrace_update_ftrace_func.
The reason for it is that graph_caller enable calling graph tracing 
which should be setup before ftrace_update_ftrace_func which enable 
whole tracing function.

# cd ; mkdir /debug; mount -t debugfs none /debug; cat 
/debug/tracing/available_tracers; echo function_graph > 
/debug/tracing/current_tracer;echo 0 > /debug/tra
cing/tracing_enabled;cat /debug/tracing/trace | head -n 10
function_graph function sched_switch nop

ftrace_update_ftrace_func 0xc0009100 0xc00091c4, 0xb000c000, 0x32809100
ftrace_enable_ftrace_graph_caller
# tracer: function_graph

For disabling graph trace is sequence ok I think.

# echo function > /debug/tracing/current_tracer
ftrace_disable_ftrace_graph_caller
ftrace_update_ftrace_func 0xc006afe4 0xc00091c4, 0xb000c006, 0x3280afe4

What do you think?

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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