From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [RFC][PATCH] irq: remove IRQF_DISABLED Date: Fri, 06 Mar 2009 19:58:42 +1100 Message-ID: <1236329922.7260.127.camel@pasglop> References: <1235996477.5330.174.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from gate.crashing.org ([63.228.1.57]:49443 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751662AbZCFI7u (ORCPT ); Fri, 6 Mar 2009 03:59:50 -0500 In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , lkml , linux-arch , Andrew Morton On Mon, 2009-03-02 at 09:11 -0800, Linus Torvalds wrote: > > On Mon, 2 Mar 2009, Peter Zijlstra wrote: > > > > Would you be willing to take such a patch? > > Yes - some day. > > The "irq's disabled fastpath" thing has been there since pretty much day > one, because some irq handlers always wanted it. Making it the default > (and the only choice) is fine. .../... I tend to disagree... (not -that- strongly but I felt like saying it anyway :-) some archs have a reasonably nice support in the PIC for interrupt priorities, allowing higher priority interrupts to "preempt" lower priority ones, which this would effectively render useless. Also, while yes, I agree, interrupts handlers -should- be short in practice IDE is far from being the only example where this is not the case and so we would delay timer interrupts for example for a significant amount of time (or serial, that's another good example). Also, we use the priority on some platform to have a high priority used as a kind of "debugger" NMI .. ie, we don't have a real NMI but it's better than nothing and here too, this would break it. I don't see us having such a strong benefit from this... in fact, with things like -rt, interrupts get moved to threads no ? Thus they typically run with interrupts enabled... why have a different behaviour on non-rt ? or I am missing something ? (I'm not terribly familiar with the -rt stuff here so I probably am missing something). Cheers, Ben.