From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753978AbdIDRav (ORCPT ); Mon, 4 Sep 2017 13:30:51 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:60492 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753951AbdIDRat (ORCPT ); Mon, 4 Sep 2017 13:30:49 -0400 From: Marc Zyngier To: Lorenzo Pieralisi , Suzuki K Poulose , Pawel Moll , Mark Rutland Cc: linux-kernel@vger.kernel.org Subject: [PATCH 1/2] bus: arm-ccn: Fix use of smp_processor_id() in preemptible context Date: Mon, 4 Sep 2017 18:30:40 +0100 Message-Id: <20170904173041.14119-2-marc.zyngier@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170904173041.14119-1-marc.zyngier@arm.com> References: <20170904173041.14119-1-marc.zyngier@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Booting a DEBUG_PREEMPT enabled kernel on a CCN-based system results in the following splat: [...] arm-ccn e8000000.ccn: No access to interrupts, using timer. BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 caller is debug_smp_processor_id+0x1c/0x28 CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.13.0 #6111 Hardware name: AMD Seattle/Seattle, BIOS 17:08:23 Jun 26 2017 Call trace: [] dump_backtrace+0x0/0x278 [] show_stack+0x24/0x30 [] dump_stack+0x8c/0xb0 [] check_preemption_disabled+0xfc/0x100 [] debug_smp_processor_id+0x1c/0x28 [] arm_ccn_probe+0x358/0x4f0 [...] as we use smp_processor_id() in the wrong context. Turning this into a get_cpu()/put_cpu() does the trick. Signed-off-by: Marc Zyngier --- drivers/bus/arm-ccn.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/bus/arm-ccn.c b/drivers/bus/arm-ccn.c index e8c6946fed9d..8502f1767024 100644 --- a/drivers/bus/arm-ccn.c +++ b/drivers/bus/arm-ccn.c @@ -1297,7 +1297,8 @@ static int arm_ccn_pmu_init(struct arm_ccn *ccn) } /* Pick one CPU which we will use to collect data from CCN... */ - cpumask_set_cpu(smp_processor_id(), &ccn->dt.cpu); + cpumask_set_cpu(get_cpu(), &ccn->dt.cpu); + put_cpu(); /* Also make sure that the overflow interrupt is handled by this CPU */ if (ccn->irq) { -- 2.11.0