linux-kernel - Re: [PATCH -tip 02/13] [CLEANUP]tracing/kprobes: merge trace probe enable/disable functions

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Date:	Sat, 09 Jul 2011 13:41:14 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, yrl.pp-manager.tt@...achi.com,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH -tip 02/13] [CLEANUP]tracing/kprobes: merge trace probe
 enable/disable functions

(2011/07/09 1:37), Steven Rostedt wrote:
> On Mon, 2011-06-27 at 16:26 +0900, Masami Hiramatsu wrote:
>> Merge redundant enable/disable functions into enable_trace_probe()
>> and disable_trace_probe().
>>
>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: Frederic Weisbecker <fweisbec@...il.com>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> ---
>>
>>  kernel/trace/trace_kprobe.c |   88 +++++++++++++++++--------------------------
>>  1 files changed, 34 insertions(+), 54 deletions(-)
>>
>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
>> index bad87e9..ce5e6aa 100644
>> --- a/kernel/trace/trace_kprobe.c
>> +++ b/kernel/trace/trace_kprobe.c
>> @@ -683,6 +683,34 @@ static struct trace_probe *find_trace_probe(const char
*event,
>>  	return NULL;
>>  }
>>
>> +/* Enable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
>> +static int enable_trace_probe(struct trace_probe *tp, int flag)
>> +{
>> +	int ret = 0;
>> +
>> +	tp->flags |= flag;
>> +	if (tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) {
>> +		if (trace_probe_is_return(tp))
>> +			ret = enable_kretprobe(&tp->rp);
>> +		else
>> +			ret = enable_kprobe(&tp->rp.kp);
>> +	}
>
> Hmm, this seems weird. Should we have any protection here? I mean, is it
> ok to call the enable_kprobe() twice? Or should we have something like:
>
> {
> 	int old_flags = tp->flags;
> 	int ret = 0;
>
> 	tp->flags |= flag;
>
> 	if (!(old_flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) &&
> 	    flag & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) {
> 		[...]
> 	}
>
> 	return ret;
> }


Ah, no problem, enable_kprobe() enables given kprobe only if it is
disabled.

>
>
>> +
>> +	return ret;
>> +}
>> +
>> +/* Disable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
>> +static void disable_trace_probe(struct trace_probe *tp, int flag)
>> +{
>> +	tp->flags &= ~flag;
>> +	if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
>> +		if (trace_probe_is_return(tp))
>> +			disable_kretprobe(&tp->rp);
>> +		else
>> +			disable_kprobe(&tp->rp.kp);
>> +	}
>> +}
>
> Same here.

Same as above.

>
> Or do we want to reenable or re disable the probe?

Yeah, we do it for enabling/disabling each event.

Thank you,


>
> -- Steve

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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