linux-kernel - Re: How about limiting refresh ioctl to sampling events ?

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Message-ID: <m3vd3o5g9u.fsf@gmail.com>
Date:	Tue, 23 Nov 2010 14:19:25 +0100
From:	Franck Bui-Huu <vagabon.xyz@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Franck Bui-Huu <vagabon.xyz@...il.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: How about limiting refresh ioctl to sampling events ?

Peter Zijlstra <a.p.zijlstra@...llo.nl> writes:

> On Tue, 2010-11-23 at 14:01 +0100, Franck Bui-Huu wrote:
>> Hello Peter,
>> 
>> I'm looking at the perf event stuff and wondering if
>
>> perf_event_refresh() should be limited to sampling events.
>> 
>> Does the following make sense ?
>> 
>> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
>> index 3b105e0..1a90a6c 100644
>> --- a/kernel/perf_event.c
>> +++ b/kernel/perf_event.c
>> @@ -1072,7 +1072,7 @@ static int perf_event_refresh(struct perf_event *event, int refresh)
>>  	/*
>>  	 * not supported on inherited events
>>  	 */
>> -	if (event->attr.inherit)
>> +	if (event->attr.inherit || !event->attr.sample_period)
>>  		return -EINVAL;
>>  
>>  	atomic_add(refresh, &event->event_limit);
>
> Yes it does, please submit as a proper patch.

Ok.

I'm also wondering if you would accept a second patch which will
introduce:

static inline bool is_sampling_event(struct perf_event *event)
{
        return event->attr.sample_period != 0;
}

That would make the code slighlty easier to read IMHO.

-- 
		Franck
--
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