linux-kernel - Re: [PATCH 14/18] 2.6.17.9 perfmon2 patch for review: new i386 files

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Message-ID: <20060828161000.GF20394@frankl.hpl.hp.com>
Date:	Mon, 28 Aug 2006 09:10:00 -0700
From:	Stephane Eranian <eranian@....hp.com>
To:	Andi Kleen <ak@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/18] 2.6.17.9 perfmon2 patch for review: new i386 files

Andi,

On Wed, Aug 23, 2006 at 12:58:55PM +0200, Andi Kleen wrote:
> 
> > +
> > +fastcall void smp_pmu_interrupt(struct pt_regs *regs)
> > +{
> 
> This misses enter/exit_idle on x86-64.
> 
I have been working on adding idle notifier for i386.
I am wondering about this code:

/* Called from interrupts to signify idle end */
void exit_idle(void)
{
        if (current->pid | read_pda(irqcount))
                return;
        __exit_idle();
}

And in particular the irqcount. I am guessing you are trying
to protect against nested interrupts. In fact, I think we only
want to get notified once the interrupt stack is fully unwound.
because we get way more exit_idle() than enter_idle().

Is there an irqcount mechanism on i386?

Thanks

--
-Stephane
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