linux-kernel - Re: [RFA][PATCH 25/27] arm64, ftrace: Remove check of obsolete variable function_trace

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Date:	Tue, 01 Jul 2014 20:33:07 +0900
From:	AKASHI Takahiro <takahiro.akashi@...aro.org>
To:	Will Deacon <will.deacon@....com>,
	Steven Rostedt <rostedt@...dmis.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Jiri Kosina <jkosina@...e.cz>,
	Josh Poimboeuf <notifications@...hub.com>
Subject: Re: [RFA][PATCH 25/27] arm64, ftrace: Remove check of obsolete variable
 function_trace_stop

On 06/27/2014 09:44 PM, Will Deacon wrote:
> Hi Steve,
>
> On Thu, Jun 26, 2014 at 05:52:46PM +0100, Steven Rostedt wrote:
>> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
>>
>> Nothing sets function_trace_stop to disable function tracing anymore.
>> Remove the check for it in the arch code.
>>
>> arm64 was broken anyway, as it had an ifdef testing
>>   CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST which is only set if
>> the arch supports the code (which it obviously did not), and
>> it was testing a non existent ftrace_trace_stop instead of
>> function_trace_stop.
>
> Yeah, the current code is total crap. Well spotted.

Thank you for fixing my bug :)
I also exercised ftrace with sysfs interface, and it just works well.

-Takahiro AKASHI

>
>> Cc: AKASHI Takahiro <takahiro.akashi@...aro.org>
>> Cc: Will Deacon <will.deacon@....com>
>> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
>> ---
>>   arch/arm64/kernel/entry-ftrace.S | 5 -----
>>   1 file changed, 5 deletions(-)
>
>    Acked-by: Will Deacon <will.deacon@....com>
>
> I'm happy for you to take this via the ftrace tree, along with the rest of
> the series.
>
> I successfully ran the ftrace self tests with this applied (on top of
> "ftrace: Remove check for HAVE_FUNCTION_TRACE_MCOUNT_TEST"), but note
> that I don't have a platform with working suspend/resume right now.
>
> Cheers,
>
> Will
>
>> diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
>> index b051871f2965..1b1e330e6849 100644
>> --- a/arch/arm64/kernel/entry-ftrace.S
>> +++ b/arch/arm64/kernel/entry-ftrace.S
>> @@ -96,11 +96,6 @@
>>    *     - ftrace_graph_caller to set up an exit hook
>>    */
>>   ENTRY(_mcount)
>> -#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
>> -	ldr	x0, =ftrace_trace_stop
>> -	ldr	x0, [x0]		// if ftrace_trace_stop
>> -	ret				//   return;
>> -#endif
>>   	mcount_enter
>>
>>   	ldr	x0, =ftrace_trace_function
>> --
>> 2.0.0
>>
>>
>>
--
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