linux-kernel - Re: [PATCH] synchronize

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Date:	Sat, 20 Oct 2007 14:06:01 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	akpm <akpm@...ux-foundation.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linuxppc-dev list <linuxppc-dev@...abs.org>
Subject: Re: [PATCH] synchronize_irq needs a barrier


> >  - even when you ignore the interrupt (because the driver doesn't care, 
> >    it's suspending), you need to make sure the hardware gets shut up by 
> >    reading (or writing) the proper interrupt status register.
> I agree, but while device is powered off, its registers can't be accessed
> Thus, if I ack the IRQ every time the handler is called, I will access the 
> powered off device (this is probably won't hurt a lot, but a bit incorrectly)

It will actually crash your machine on some platforms. So no, best is to
-not- ack. The masking is enough, the IRQ will go down eventually.

Ben.


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