linux-kernel - Re: [tip:perf/core] perf: Remove the nmi parameter from the swevent and overflow interface

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Date:	Fri, 8 Jul 2011 18:34:42 +0100
From:	Will Deacon <will.deacon@....com>
To:	"mingo@...hat.com" <mingo@...hat.com>,
	"dengcheng.zhu@...il.com" <dengcheng.zhu@...il.com>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"anton@...ba.org" <anton@...ba.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jason.wessel@...driver.com" <jason.wessel@...driver.com>,
	"lethal@...ux-sh.org" <lethal@...ux-sh.org>,
	"emunson@...bm.net" <emunson@...bm.net>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"mcree@...on.net.nz" <mcree@...on.net.nz>,
	"mingo@...e.hu" <mingo@...e.hu>
Cc:	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:perf/core] perf: Remove the nmi parameter from the
 swevent and overflow interface

Hi Peter,

On Fri, Jul 01, 2011 at 04:21:25PM +0100, tip-bot for Peter Zijlstra wrote:
> Commit-ID:  a8b0ca17b80e92faab46ee7179ba9e99ccb61233
> Gitweb:     http://git.kernel.org/tip/a8b0ca17b80e92faab46ee7179ba9e99ccb61233
> Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
> AuthorDate: Mon, 27 Jun 2011 14:41:57 +0200
> Committer:  Ingo Molnar <mingo@...e.hu>
> CommitDate: Fri, 1 Jul 2011 11:06:35 +0200
> 
> perf: Remove the nmi parameter from the swevent and overflow interface
> 
> The nmi parameter indicated if we could do wakeups from the current
> context, if not, we would set some state and self-IPI and let the
> resulting interrupt do the wakeup.
> 
> For the various event classes:
> 
>   - hardware: nmi=0; PMI is in fact an NMI or we run irq_work_run from
>     the PMI-tail (ARM etc.)
>   - tracepoint: nmi=0; since tracepoint could be from NMI context.
>   - software: nmi=[0,1]; some, like the schedule thing cannot
>     perform wakeups, and hence need 0.
> 
> As one can see, there is very little nmi=1 usage, and the down-side of
> not using it is that on some platforms some software events can have a
> jiffy delay in wakeup (when arch_irq_work_raise isn't implemented).
> 
> The up-side however is that we can remove the nmi parameter and save a
> bunch of conditionals in fast paths.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

Whilst you updated the arch code in this series, you forgot to update the
oprofile perf backend. I think you want something as simple as:


diff --git a/drivers/oprofile/oprofile_perf.c b/drivers/oprofile/oprofile_perf.c
index 59acf9e..94796f3 100644
--- a/drivers/oprofile/oprofile_perf.c
+++ b/drivers/oprofile/oprofile_perf.c
@@ -31,7 +31,7 @@ static int num_counters;
 /*
  * Overflow callback for oprofile.
  */
-static void op_overflow_handler(struct perf_event *event, int unused,
+static void op_overflow_handler(struct perf_event *event,
                        struct perf_sample_data *data, struct pt_regs *regs)
 {
        int id;


although I haven't tried it.

Cheers,

Will
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