From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Wed, 5 Sep 2012 14:01:26 -0700 Subject: [PATCH] ARM: Fix deadlock scenario with smp_send_stop() Message-ID: <1346878886-7159-1-git-send-email-sboyd@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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(). 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 -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932196Ab2IEVBr (ORCPT ); Wed, 5 Sep 2012 17:01:47 -0400 Received: from wolverine02.qualcomm.com ([199.106.114.251]:20103 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753937Ab2IEVBq (ORCPT ); Wed, 5 Sep 2012 17:01:46 -0400 X-IronPort-AV: E=McAfee;i="5400,1158,6826"; a="230997338" From: Stephen Boyd To: Russell King - ARM Linux Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH] ARM: Fix deadlock scenario with smp_send_stop() Date: Wed, 5 Sep 2012 14:01:26 -0700 Message-Id: <1346878886-7159-1-git-send-email-sboyd@codeaurora.org> X-Mailer: git-send-email 1.7.12.176.g3fc0e4c Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(). 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 -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation