linux-kernel - Re: [PATCH 0/5] Fix regression introduced by set_irq

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Message-ID: <20151208095835.582dc34b@free-electrons.com>
Date:	Tue, 8 Dec 2015 09:58:35 +0100
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Tawfik Bayouk <tawfik@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Lior Amsalem <alior@...vell.com>, Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>
Subject: Re: [PATCH 0/5] Fix regression introduced by set_irq_flags()
 removal

Hello Thomas,

On Sun, 6 Dec 2015 10:28:15 +0100 (CET), Thomas Gleixner wrote:

> Second thoughts. That network driver example does not make sense.
> 
> You have a suspend/resume mechanism and a cpu hotplug machinery in
> that driver, right? So that should be responsible for
> disabling/enabling the per cpu interrupts. I don't think it's the
> proper way to do that in the irq chip driver at some random point
> during resume as you'd reenable interrupts on cpus which are not
> online yet.

The irqchip driver would re-enable the per-CPU interrupts in a CPU
notifier, so only when the secondary CPUs come online again after
resume.

When a device driver uses a normal (non per-CPU) interrupt, then it
doesn't have to take care of disabling the interrupt on suspend and
re-enabling the interrupt on resume at the interrupt controller level.
This is all transparently handled by the irqchip driver.

Why should the handling of per-CPU interrupts be different and require
explicit handling from each device driver rather than being
transparently handled by the irqchip driver ?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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