linux-kernel - Re: [PATCH 3/5] MIPS/Perf-events: Check event state in validate

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Message-ID: <1290159806.9342.7.camel@e102144-lin.cambridge.arm.com>
Date:	Fri, 19 Nov 2010 09:43:26 +0000
From:	Will Deacon <will.deacon@....com>
To:	Deng-Cheng Zhu <dengcheng.zhu@...il.com>
Cc:	ralf@...ux-mips.org, a.p.zijlstra@...llo.nl, fweisbec@...il.com,
	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
	wuzhangjin@...il.com, paulus@...ba.org, mingo@...e.hu,
	acme@...hat.com
Subject: Re: [PATCH 3/5] MIPS/Perf-events: Check event state in
 validate_event()

Hi Deng-Cheng,

On Thu, 2010-11-18 at 06:56 +0000, Deng-Cheng Zhu wrote:
> Ignore events that are not for this PMU or are in off/error state.
> 
Sorry I didn't see this before, thanks for pointing out that you
had included it for MIPS.

> Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@...il.com>
> ---
>  arch/mips/kernel/perf_event.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/mips/kernel/perf_event.c b/arch/mips/kernel/perf_event.c
> index 1ee44a3..9c6442a 100644
> --- a/arch/mips/kernel/perf_event.c
> +++ b/arch/mips/kernel/perf_event.c
> @@ -486,7 +486,7 @@ static int validate_event(struct cpu_hw_events *cpuc,
>  {
>         struct hw_perf_event fake_hwc = event->hw;
> 
> -       if (event->pmu && event->pmu != &pmu)
> +       if (event->pmu != &pmu || event->state <= PERF_EVENT_STATE_OFF)
>                 return 0;
> 
>         return mipspmu->alloc_counter(cpuc, &fake_hwc) >= 0;

So this is the opposite of what we're doing on ARM. Our
approach is to ignore events that are OFF (or in the ERROR
state) or that belong to a different PMU. We do this by
allowing them to *pass* validation (i.e. by returning 1 above).
This means that we won't unconditionally fail a mixed event group.

x86 does something similar in the collect_events function.

Will

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