Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758446Ab2EXRPe (ORCPT ); Thu, 24 May 2012 13:15:34 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:36617 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757266Ab2EXRPd (ORCPT ); Thu, 24 May 2012 13:15:33 -0400 Date: Thu, 24 May 2012 18:15:24 +0100 From: Russell King - ARM Linux To: Pantelis Antoniou Cc: linux-kernel@vger.kernel.org, Russ.Dill@ti.com, mporter@ti.com, stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] [ARM] Unconditional call to smp_cross_call on UP crashes Message-ID: <20120524171524.GG6908@n2100.arm.linux.org.uk> References: <1337889024-10416-1-git-send-email-panto@antoniou-consulting.com> <20120524161733.GF6908@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1558 Lines: 38 On Thu, May 24, 2012 at 07:55:56PM +0300, Pantelis Antoniou wrote: > Hi Russell, > > On May 24, 2012, at 7:17 PM, Russell King - ARM Linux wrote: > > > On Thu, May 24, 2012 at 07:50:24PM +0000, Pantelis Antoniou wrote: > >> omap2plus_defconfig builds with SMP & SMP_ON_UP set. > >> On beagle (which is UP) is_smp() returns false and we don't call > >> smp_init_cpus which in turn does not initialize smp_cross_call which > >> remains NULL. > >> > >> When issuing a reboot we OOPS with a NULL dereference on stop smp_call. > > > > I've been wondering whether we should make smp_cross_call() a no-op instead > > by default, rather than a NULL pointer. > > > > Alternatively, if may be well worth changing this to do: > > > > if (!cpumask_empty(&mask)) > > smp_cross_call(&mask, IPI_CPU_STOP); > > > > instead, so we avoid calling smp_cross_call() when we're on a SMP system > > with only one CPU online. I like this approach better because it removes > > a potential call into platform code which is inappropriate. > > Both of these can work, and in fact have been tried. > > I am partial on both to be honest. Have a default no-op function for smp_cross_call() > and guard with cpumask_empty(). > > Which do you want me to make a patch for? I think the cpumask_empty() is the best approach, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/