linux-kernel - Re: [RFC V2 PATCH 2/6] powerpc: Implement broadcast timer interrupt as an IPI message

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Date:	Thu, 22 Aug 2013 13:10:57 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	fweisbec@...il.com, paul.gortmaker@...driver.com, paulus@...ba.org,
	shangw@...ux.vnet.ibm.com, galak@...nel.crashing.org,
	deepthi@...ux.vnet.ibm.com, paulmck@...ux.vnet.ibm.com,
	arnd@...db.de, linux-pm@...r.kernel.org, rostedt@...dmis.org,
	rjw@...k.pl, john.stultz@...aro.org, tglx@...utronix.de,
	chenhui.zhao@...escale.com, michael@...erman.id.au,
	r58472@...escale.com, geoff@...radead.org,
	linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com,
	schwidefsky@...ibm.com, svaidy@...ux.vnet.ibm.com,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC V2 PATCH 2/6] powerpc: Implement broadcast timer interrupt
 as an IPI message

On Wed, 2013-08-14 at 17:26 +0530, Preeti U Murthy wrote:
> -static irqreturn_t unused_action(int irq, void *data)
> +static irqreturn_t timer_action(int irq, void *data)
>  {
> -       /* This slot is unused and hence available for use, if needed
> */
> +       timer_interrupt();
>         return IRQ_HANDLED;
>  }
>  

That means we'll do irq_enter/irq_exit twice no ? And things like
may_hard_irq_enable() are also already done by do_IRQ so you
don't need timer_interrupt() to do it again.

We probably are better off breaking timer_interrupt in two:

void __timer_interrupt(struct pt_regs * regs)

Does the current stuff between irq_enter and irq_exit, timer_interrupt
does the remaining around it and calls __timer_interrupt.

Then from timer_action, you call __timer_interrupt()

Cheers,
Ben.



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