From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Balbi Subject: Re: [PATCH 2/2] i2c: i2c-omap: Call request_irq with IRQF_DISABLED Date: Thu, 12 Mar 2009 02:23:54 +0200 Message-ID: <20090312002353.GD19038@gandalf> References: <7d7e7dd1a4c64c732a21bdfcf2bd42556be708c3.1236345858.git.Ext-Ari.Kauppi@nokia.com> <20090310005222.GE19758@fluff.org.uk> <20090311235908.GC19038@gandalf> Reply-To: me@felipebalbi.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-omap-owner@vger.kernel.org To: Paul Walmsley Cc: Felipe Balbi , Ari Kauppi , Ben Dooks , ben-linux@fluff.org, linux-omap@vger.kernel.org, linux-i2c@vger.kernel.org List-Id: linux-i2c@vger.kernel.org On Wed, Mar 11, 2009 at 06:07:00PM -0600, Paul Walmsley wrote: > Hi Felipe, > > On Thu, 12 Mar 2009, Felipe Balbi wrote: > > > On Wed, Mar 11, 2009 at 05:55:50PM -0600, Paul Walmsley wrote: > > > Ben's right, there shouldn't be any need for this. This patch could cause > > > some unnecessary interrupt service latency. > > > > That's not what Thomas Gleixner thinks. How about the possibility of > > stack overflow ? > > That sounds like a separate issue from the spurious IRQ problem that the > patch was intended to fix. > > I'm not familiar with the discussion on the stack overflow issue. Could > you send a link? This is the link where Ingo discusses why !IRQF_DISABLED could cause stack overflow: http://lkml.org/lkml/2009/3/3/71 You probably wanna take a look at the whole thread to figure out the discussion, but basically Ingo and Peter (Zijlstra) believe !IRQF_DISABLED is a bug and drivers needing that probably should be using threaded irqs (which is not yet merged) or the hw is broken, and for those an IRQF_ENABLED flag will be created and a TAINT will also be placed. Once that gets merged, all drivers will be forced (at some point) to IRQF_DISABLED and those which don't want that will be moved gradually to threaded irq. This patch is also interesting: http://lkml.org/lkml/2009/3/2/33 -- balbi