From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757826Ab2IKSJA (ORCPT ); Tue, 11 Sep 2012 14:09:00 -0400 Received: from wolverine01.qualcomm.com ([199.106.114.254]:8751 "EHLO wolverine01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757388Ab2IKSI7 (ORCPT ); Tue, 11 Sep 2012 14:08:59 -0400 X-IronPort-AV: E=McAfee;i="5400,1158,6832"; a="235399107" Message-ID: <504F7E3A.8020808@codeaurora.org> Date: Tue, 11 Sep 2012 11:08:58 -0700 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:15.0) Gecko/20120907 Thunderbird/15.0.1 MIME-Version: 1.0 To: Russell King - ARM Linux CC: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] ARM: Fix deadlock scenario with smp_send_stop() References: <1346878886-7159-1-git-send-email-sboyd@codeaurora.org> In-Reply-To: <1346878886-7159-1-git-send-email-sboyd@codeaurora.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/12 14:01, Stephen Boyd wrote: > If one process calls sys_reboot and that process then stops other > CPUs while those CPUs are within a spin_lock() region we can > potentially encounter a deadlock scenario like below. > > CPU 0 CPU 1 > ----- ----- > spin_lock(my_lock) > smp_send_stop() > send_IPI handle_IPI() > disable_preemption/irqs > while(1); > > spin_lock(my_lock) <--- Waits forever > > We shouldn't attempt to run any other tasks after we send a stop > IPI to a CPU so disable preemption so that the reboot task runs to > completion. > > Reported-by: Sundarajan Srinivasan > Signed-off-by: Stephen Boyd > --- > > Unfortunately this won't fix the other problem I mentioned two weeks > ago where smp_send_stop races with other CPUs calling cpu_up(). Any comments? > > arch/arm/kernel/process.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c > index 693b744..663a7a8 100644 > --- a/arch/arm/kernel/process.c > +++ b/arch/arm/kernel/process.c > @@ -239,6 +239,7 @@ __setup("reboot=", reboot_setup); > > void machine_shutdown(void) > { > + preempt_disable(); > #ifdef CONFIG_SMP > smp_send_stop(); > #endif -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation