Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752020AbdGIIbq (ORCPT ); Sun, 9 Jul 2017 04:31:46 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:9807 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750859AbdGIIbp (ORCPT ); Sun, 9 Jul 2017 04:31:45 -0400 From: Ding Tianhong Subject: [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround To: Mark Rutland , Marc Zyngier , Catalin Marinas , Will Deacon , LinuxArm , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Message-ID: <321e4c16-aa14-beee-b6dc-36e19e5ec35a@huawei.com> Date: Sun, 9 Jul 2017 16:30:54 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.23.32] X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.5961E9CE.00F6,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 8fe5dbb3e72fafa57868c208cf6da254 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1646 Lines: 43 When enable preempt and debug ftrace, and perform the following steps, the system will hang: mount -t debugfs nodev /sys/kernel/debug/ cd /sys/kernel/debug/tracing/ echo function_graph > current_tracer This is because tracing the preempt_disable/enable calls would cause trace_clock() which would get local timer to go into infinite recursion when enable the arch timer erratum workaround for some chips, so Prevent tracing of preempt_disable/enable() in arch_timer_reg_read_stable(). This problem is similar to the fixed by upstream commit 96b3d28bf4 ("sched/clock: Prevent tracing recursion in sched_clock_cpu()"). Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs") Signed-off-by: Ding Tianhong --- arch/arm64/include/asm/arch_timer.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 74d08e4..67bb7a4 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround { u64 _val; \ if (needs_unstable_timer_counter_workaround()) { \ const struct arch_timer_erratum_workaround *wa; \ - preempt_disable(); \ + preempt_disable_notrace(); \ wa = __this_cpu_read(timer_unstable_counter_workaround); \ if (wa && wa->read_##reg) \ _val = wa->read_##reg(); \ else \ _val = read_sysreg(reg); \ - preempt_enable(); \ + preempt_enable_notrace(); \ } else { \ _val = read_sysreg(reg); \ } \ -- 1.9.0