linux-kernel - Re: [RFA][PATCH 07/27] MIPS: ftrace: Add call to ftrace_graph_is

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Date:	Wed, 9 Jul 2014 16:48:32 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	Steven Rostedt <rostedt@...dmis.org>, <linux-mips@...ux-mips.org>
CC:	<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>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Jiri Kosina <jkosina@...e.cz>,
	Josh Poimboeuf <notifications@...hub.com>,
	Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [RFA][PATCH 07/27] MIPS: ftrace: Add call to ftrace_graph_is_dead()
 in function graph code

Hi Steven,

I've given this a quick test on a mips32 le target, on your
rfc/remove-function-trace-stop branch (4161daee7df8). Booted fine,
startup tests fine, function and function_graph trace appear to work
from a quick cat of the trace file. Feel free to add my Tested-by:

Tested-by: James Hogan <james.hogan@...tec.com> [MIPS]

Cheers
James

On 02/07/14 15:31, Steven Rostedt wrote:
> 
> Adding linux-mips@...ux-mips.org.
> 
> -- Steve
> 
> 
> On Thu, 26 Jun 2014 12:52:28 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
>> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
>>
>> ftrace_stop() is going away as it disables parts of function tracing
>> that affects users that should not be affected. But ftrace_graph_stop()
>> is built on ftrace_stop(). Here's another example of killing all of
>> function tracing because something went wrong with function graph
>> tracing.
>>
>> Instead of disabling all users of function tracing on function graph
>> error, disable only function graph tracing. To do this, the arch code
>> must call ftrace_graph_is_dead() before it implements function graph.
>>
>> Cc: Ralf Baechle <ralf@...ux-mips.org>
>> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
>> ---
>>  arch/mips/kernel/ftrace.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
>> index 60e7e5e45af1..8b6538750fe1 100644
>> --- a/arch/mips/kernel/ftrace.c
>> +++ b/arch/mips/kernel/ftrace.c
>> @@ -302,6 +302,9 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
>>  	    &return_to_handler;
>>  	int faulted, insns;
>>  
>> +	if (unlikely(ftrace_graph_is_dead()))
>> +		return;
>> +
>>  	if (unlikely(atomic_read(&current->tracing_graph_pause)))
>>  		return;
>>  
> 
> --
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