From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.9 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE5EDC04EBF for ; Mon, 3 Dec 2018 22:46:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9747120864 for ; Mon, 3 Dec 2018 22:46:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9747120864 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gmx.us Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726004AbeLCWql (ORCPT ); Mon, 3 Dec 2018 17:46:41 -0500 Received: from mout.gmx.net ([212.227.15.18]:43325 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725920AbeLCWqk (ORCPT ); Mon, 3 Dec 2018 17:46:40 -0500 Received: from qcai.nay.com ([66.187.233.206]) by mail.gmx.com (mrgmx003 [212.227.17.184]) with ESMTPSA (Nemesis) id 0MMjgF-1gZifp0J7X-008Yqq; Mon, 03 Dec 2018 23:45:58 +0100 From: Qian Cai To: mark.rutland@arm.com, marc.zyngier@arm.com Cc: daniel.lezcano@linaro.org, tglx@linutronix.de, peterz@infradead.org, mingo@kernel.org, longman@redhat.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH v2] clocksource/arm_arch_timer: fix a lockdep warning Date: Mon, 3 Dec 2018 17:45:21 -0500 Message-Id: <1543877121-4098-1-git-send-email-cai@gmx.us> X-Mailer: git-send-email 1.8.3.1 X-Provags-ID: V03:K1:mPronifC4t5JDwHNkpMd3JGH1V/ug1P1l6n5sK0eVUFfGALXibc eYAsAzr8WfoZ1BceoyjNEyrKxz4YYVnOP+XWmU0IZds02+QOomUDr/J2827elRcX0CvS8v1 RGnRMSKnFeRPL/ICXplz74d5Jl2iFs3Rdeecp+Lqu670Fn/TEMflkchwNyEzcskq1eqUC4B hn2VFTo52enb+HXXyS0iA== X-UI-Out-Filterresults: notjunk:1;V03:K0:rZZpkZY15Ng=:Sh0VFLRGZq0mQvNXgR6FD/ mWOMVEzBekAMLwVKtL51N+6DsmcUxCt0uIXafERRppOA2pBR+iMFoPNN/keIdjyA8YQ/SUBSQ j6hHMoUhhujPy1uB/MhEL3vxRMWsT2+w7Zo3ue3TGzBKDElnxZvvbUcTOfLF3Q2k7HTo2H71m FLhu4g5Y/2bM6ykX8kfXfmDMkQZDwA5mGjwtypz2XGg6EUjlEu2nxyRTPjRdxQZ5agV3Ze7f4 zz2ExbrhFQK471YHBL2pVYTdh3ZMeUkdNS2ten5x2RcoE9DUOR0BR733ee8+jbc8j0WAPsHax 1ap07/+IT4cN24+j3XtpKvOu7Pb6Gb4DlBRbrZZQzENDFCMx1EGL1B1LsjoR1JRSN8UXT1GDW p/w3YYFzOR9AGrt4v8LQzhc8XbvXPoqXS5cWn5EVM7k0NZmQ2wIzjGRojdFoNo+RySMYiN/MG /aVG+ElOOStnLyfD+ehplpxH0rwUevAmINm89zUOcM5qaIw0hYCygNh1GFQmdRBccOyr41cT8 LBWtds1/vp7QtsO9c+JnDKPpyucTeqGUWlU8uuD5Bxsq6COn+05OP9Ctfg2FKWnXwGeppMOEA xBUKftRrmFSZQDjOEO0+pdsMTD9s4H61x1AXrOXvJE4xGnmLbI8lXft39cA+PGQHiV0j+WmzA LbTcZ0/FqbSCjZRQEyh/YXwa2KE8i8ZHTz4NvbUDffFIh60shbwmNrqmvCqwowil8vWWwq4jm NPCmgDJIcgMHAzsohz/sJc1xnosFJ+R7/t7ttHAvjK0t79MPpRPjlZABFDPRNYh1JixgmBOms luwdTSFqfUFaysYUlTlH+e/CbmXqkB+sdahroKHoRywCKChFUKdIQZdguODliiiv79739NOIy Oj/AJujuPR18D+fSYqInVz0BbZZSX3ezJ2kj6kcps= Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Booting this Huawei TaiShan 2280 arm64 server generated this lockdep warning. [ 0.000000] lockdep_assert_cpus_held+0x50/0x60 [ 0.000000] static_key_enable_cpuslocked+0x30/0xe8 [ 0.000000] arch_timer_check_ool_workaround+0x128/0x2d0 [ 0.000000] arch_timer_acpi_init+0x274/0x6ac [ 0.000000] acpi_table_parse+0x1ac/0x218 [ 0.000000] __acpi_probe_device_table+0x164/0x1ec [ 0.000000] timer_probe+0x1bc/0x254 [ 0.000000] time_init+0x44/0x98 [ 0.000000] start_kernel+0x4ec/0x7d4 This is due to the commit cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations"). Since it is applying a global workaround to all CPUs here, it did not hold any CPU locks in this path. arch_timer_acpi_init arch_timer_check_ool_workaround(ate_match_acpi_oem_info, table) arch_timer_enable_workaround(wa, local = false) for_each_possible_cpu() per_cpu() When hot-add a CPU, it will go with a slightly different route. arch_timer_starting_cpu __arch_timer_setup arch_timer_check_ool_workaround(ate_match_local_cap_id, NULL) arch_timer_enable_workaround(wa, local = true) __this_cpu_write() Hence, deal with them differently. Fixes: 450f9689f294 (clocksource/arm_arch_timer: Use static_branch_enable_cpuslocked()) Signed-off-by: Qian Cai --- Changes since v1: * Fixed the root cause instead of a workaround. drivers/clocksource/arm_arch_timer.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 9a7d4dc00b6e..81dca7d31d13 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -492,18 +492,21 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa if (local) { __this_cpu_write(timer_unstable_counter_workaround, wa); + + /* + * Use the locked version, as we're called from the CPU + * hotplug framework. Otherwise, we end-up in + * deadlock-land. + */ + static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled); } else { for_each_possible_cpu(i) per_cpu(timer_unstable_counter_workaround, i) = wa; + /* A global workaround is not on the CPU hotplug path. */ + static_branch_enable(&arch_timer_read_ool_enabled); } /* - * Use the locked version, as we're called from the CPU - * hotplug framework. Otherwise, we end-up in deadlock-land. - */ - static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled); - - /* * Don't use the vdso fastpath if errata require using the * out-of-line counter accessor. We may change our mind pretty * late in the game (with a per-CPU erratum, for example), so -- 1.8.3.1