From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751709Ab0CYMAX (ORCPT ); Thu, 25 Mar 2010 08:00:23 -0400 Received: from one.firstfloor.org ([213.235.205.2]:39258 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751283Ab0CYMAW (ORCPT ); Thu, 25 Mar 2010 08:00:22 -0400 Date: Thu, 25 Mar 2010 13:00:21 +0100 From: Andi Kleen To: Thomas Gleixner Cc: Alan Cox , Andi Kleen , x86@kernel.org, LKML , jesse.brandeburg@intel.com, Linus Torvalds Subject: Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2 Message-ID: <20100325120021.GN20695@one.firstfloor.org> References: <20100324190150.GA18803@basil.fritz.box> <20100325003652.GG20695@one.firstfloor.org> <20100325105033.35bceffd@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 25, 2010 at 12:16:17PM +0100, Thomas Gleixner wrote: > > Pretty much the only 'core' driver today which enables IRQs in the irq > > handlers and needs it is the old IDE layer. There are also a couple of > > drivers which play games with disable/enable_irq in the IRQ paths for > > other reasons (lack of irq threads when written and a hardware model thats > > totally SMP unfriendly). 8390 is the obvious one here and it at least > > would be far far saner using threaded IRQs and normal locking with IRQs > > unmasked. > > Right, but that's not the problem here. We talk about a (hopefully) > well written interrupt handler which runs for a very short > time. The NIC handlers can do quite some work under high traffic. Even with interrupt mitigation and NAPI. > What's the point of running it with interrupts enabled ? Other interrupts. > Nothing, we just run into stack overflow problems. So what's better: > an unreliable and ugly hackaround I don't think that's a accurate description of the patch at all. Besides I believe it's reliable in all cases that matter. -Andi -- ak@linux.intel.com -- Speaking for myself only.