linux-kernel - Re: [PATCH] ftrace: use helper function clear_ftrace

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Message-ID: <17da0ae7-32dc-fc7f-0a87-24d243510e88@huawei.com>
Date:   Tue, 30 Jan 2018 19:39:23 +0800
From:   Yisheng Xie <xieyisheng1@...wei.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     <mingo@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: use helper function clear_ftrace_function

Hi Steve,

On 2018/1/30 18:13, Steven Rostedt wrote:
> On Tue, 30 Jan 2018 08:46:01 +0800
> Yisheng Xie <xieyisheng1@...wei.com> wrote:
> 
>> We have helper function clear_ftrace_function(), use it instead of hard
>> code. And this should not have any functional change.
>>
>> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>
>> ---
>>  kernel/trace/ftrace.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
>> index 554b517..ba78e03 100644
>> --- a/kernel/trace/ftrace.c
>> +++ b/kernel/trace/ftrace.c
>> @@ -6779,7 +6779,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
>>  
>>  	} else {
>>  		/* stopping ftrace calls (just send to ftrace_stub) */
>> -		ftrace_trace_function = ftrace_stub;
>> +		clear_ftrace_function();
>>  
>>  		ftrace_shutdown_sysctl();
>>  	}
> 
> Honestly, I rather nuke that function and clear_ftrace_function_probe()

Do you means clear_ftrace_function_probes() ? I do not find clear_ftrace_function_probe
in mainline or trace tree:
  https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git/

clear_ftrace_function_probes() is used in trace.c instead of ftrace.c, and meanwhile it
has a local variable:

	struct ftrace_func_probe *probe, *n;

which defined in ftrace.c. So I am a litter puzzle about how to nuke it without moving
struct ftrace_func_probe 's definition to first class.

I'm not sure whether I am missing anything.

> along with it. They are not used outside of ftrace.c and they don't
> actually help.

For clear_ftrace_function it really can be nuked, for it's only used in ftrace.c.

Thanks
Yisheng

> 
> -- Steve
> 
>