From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753283AbXJTEGU (ORCPT ); Sat, 20 Oct 2007 00:06:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751878AbXJTEGN (ORCPT ); Sat, 20 Oct 2007 00:06:13 -0400 Received: from gate.crashing.org ([63.228.1.57]:39094 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751845AbXJTEGN (ORCPT ); Sat, 20 Oct 2007 00:06:13 -0400 Subject: Re: [PATCH] synchronize_irq needs a barrier From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Maxim Levitsky Cc: Linus Torvalds , akpm , Linux Kernel list , linuxppc-dev list In-Reply-To: <200710200510.01409.maximlevitsky@gmail.com> References: <1192670742.12879.5.camel@pasglop> <200710200402.43106.maximlevitsky@gmail.com> <200710200510.01409.maximlevitsky@gmail.com> Content-Type: text/plain Date: Sat, 20 Oct 2007 14:06:01 +1000 Message-Id: <1192853161.17235.34.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > - 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.