From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756865Ab3ANOR3 (ORCPT ); Mon, 14 Jan 2013 09:17:29 -0500 Received: from www.linutronix.de ([62.245.132.108]:58989 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752999Ab3ANOR2 (ORCPT ); Mon, 14 Jan 2013 09:17:28 -0500 Date: Mon, 14 Jan 2013 15:17:26 +0100 (CET) From: Thomas Gleixner To: Mark Rutland cc: "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "nico@linaro.org" , Will Deacon , Marc Zyngier , "john.stultz@linaro.org" Subject: Re: [PATCHv2 1/4] clockevents: Add generic timer broadcast receiver In-Reply-To: <20130114121247.GD7990@e106331-lin.cambridge.arm.com> Message-ID: References: <1357742770-15028-1-git-send-email-mark.rutland@arm.com> <1357742770-15028-2-git-send-email-mark.rutland@arm.com> <20130114112951.GC7990@e106331-lin.cambridge.arm.com> <20130114121247.GD7990@e106331-lin.cambridge.arm.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 14 Jan 2013, Mark Rutland wrote: > On Mon, Jan 14, 2013 at 11:50:55AM +0000, Thomas Gleixner wrote: > > On Mon, 14 Jan 2013, Mark Rutland wrote: > > > > > On Mon, Jan 14, 2013 at 11:06:31AM +0000, Thomas Gleixner wrote: > > > > On Wed, 9 Jan 2013, Mark Rutland wrote: > > > > > +#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST > > > > > +extern int tick_receive_broadcast(void); > > > > > +#else > > > > > +static inline int tick_receive_broadcast(void) > > > > > +{ > > > > > + return 0; > > > > > +} > > > > > > > > What's the inline function for? If an arch does not have broadcasting > > > > support it should not have a receive broadcast function call either. > > > > > > That was how this was originally structured [1], but Santosh suggested this > > > would break the build for !GENERIC_CLOCKEVENTS_BROADCAST [1]. It means that the > > > arch-specific receive path (i.e. IPI handler) doesn't have to be #ifdef'd, > > > which makes it less ugly. > > > > Hmm. If you want to keep the IPI around unconditionally the inline > > makes some sense, though the question is whether keeping an unused IPI > > around makes sense in the first place. I'd rather see a warning that > > an unexpected IPI happened than a silent inline function being called. > > How about I add a warning (e.g. "Impossible timer broadcast received.") and > return -EOPNOTSUPP when !GENERIC_CLOCKEVENTS_BROADCAST? You still need to do something with the return value in the arch IPI code, right? > > > > Is anything going to use the return value? > > > > > > I'd added this after looking at the x86 lapic timers, where interrupts might > > > remain pending over a kexec, and lapic interrupts come up before timers are > > > registered. The return value is useful for shutting down the timer in that case > > > (see x86's local_apic_timer_interrupt). > > > > Right, though then you need to check for evt->event_handler as well. > > I thought this previously also [1], but I couldn't find any path such that a > tick_cpu_device would have an evtdev without an event_handler. We always set the > handler before setting evtdev, and alway wipe evtdev before wiping the handler. > > Have I missed something? That's an x86 specific issue. Though we could try and make that functionality completely generic. Thanks, tglx