From mboxrd@z Thu Jan  1 00:00:00 1970
From: mark.rutland@arm.com (Mark Rutland)
Date: Wed, 19 Apr 2017 16:07:25 +0100
Subject: [PATCH v24 09/11] acpi/arm64: Add memory-mapped timer support in
 GTDT driver
In-Reply-To: <20170418172107.GA1401@red-moon>
References: <20170414184014.8524-1-fu.wei@linaro.org>
 <20170414184014.8524-10-fu.wei@linaro.org>
 <20170418172107.GA1401@red-moon>
Message-ID: <20170419150725.GH27829@leverpostej>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Apr 18, 2017 at 06:21:07PM +0100, Lorenzo Pieralisi wrote:
> On Sat, Apr 15, 2017 at 02:40:12AM +0800, fu.wei at linaro.org wrote:

> > +error:
> > +	for (i = 0; i < ARCH_TIMER_MEM_MAX_FRAMES; i++) {
> > +		frame = &timer_mem->frame[i];
> > +		if (frame->phys_irq > 0)
> > +			acpi_unregister_irq(frame->phys_irq);
> > +		if (frame->virt_irq > 0)
> > +			acpi_unregister_irq(frame->virt_irq);
> > +	}
> 
> There are three error paths, none of them reset [i,gtdt_frame],
> correct ?

Correct.

> If yes, why can't it simply be written like this ?
> 
> for (; i >= 0; i--, gtdt_frame--) {
> 	frame = &timer_mem->frame[gtdt_frame->frame_number];
> 
> 	/* not sure this check is actually needed */
> 	if (gtdt_frame->common_flags & ACPI_GTDT_GT_IS_SECURE_TIMER)
> 		continue;
> 
> 	if (frame->phys_irq > 0)
> 		acpi_unregister_gsi(gtdt_frame->timer_interrupt);
> 	if (frame->virt_irq > 0)
> 		acpi_unregister_gsi(gtdt_frame->virtual_timer_interrupt);
> }

A reverse loop of this form will work.

That requires some restructuring, and care to avoid going out of bounds
instantaneously with the gtdt_frame--, so as to not invoke nasal demons.

I've attacked this locally, and will send this out after testing. I'll
drop the new ACPI API patch.

Thanks,
Mark.