From nobody Wed Feb 11 06:53:36 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 80FF4C7619A for ; Wed, 5 Apr 2023 17:30:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232923AbjDERaR (ORCPT ); Wed, 5 Apr 2023 13:30:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46590 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233638AbjDER35 (ORCPT ); Wed, 5 Apr 2023 13:29:57 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB4426A5A for ; Wed, 5 Apr 2023 10:28:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680715731; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=GPqtHGUUdaGMWj+r62KgPaCWtTqZFGGxhe2WBH2SAZQ=; b=dKfPiQA6BAAutZCGHfi9HFDycnmnIzn1N6UINI8LZ0W0HZ1W0IPU0l7ZkakqacGgSCkd2o KTqBKi6NXVj1Ie9uDJJ+JuX09aD2Pwe6Z2dMaK7jg/cqsrtKFMSOC1nPfPkMiDe68NsG3V cZHMmszg0r3CT1PtY5moSUj1+SQeTog= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-616-qymVOFufN7GrAuaKToXmBQ-1; Wed, 05 Apr 2023 13:28:49 -0400 X-MC-Unique: qymVOFufN7GrAuaKToXmBQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 43936381458A; Wed, 5 Apr 2023 17:28:49 +0000 (UTC) Received: from llong.com (dhcp-17-153.bos.redhat.com [10.18.17.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0C647C1602A; Wed, 5 Apr 2023 17:28:49 +0000 (UTC) From: Waiman Long To: Will Deacon , Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH] perf/arm-dmc620: Reverse locking order in dmc620_pmu_get_irq() Date: Wed, 5 Apr 2023 13:28:42 -0400 Message-Id: <20230405172842.2663770-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The following circular locking dependency was reported when running cpus online/offline test on an arm64 system. [ 84.195923] Chain exists of: dmc620_pmu_irqs_lock --> cpu_hotplug_lock --> cpuhp_state-= down [ 84.207305] Possible unsafe locking scenario: [ 84.213212] CPU0 CPU1 [ 84.217729] ---- ---- [ 84.222247] lock(cpuhp_state-down); [ 84.225899] lock(cpu_hotplug_lock); [ 84.232068] lock(cpuhp_state-down); [ 84.238237] lock(dmc620_pmu_irqs_lock); [ 84.242236] *** DEADLOCK *** The problematic locking order seems to be lock(dmc620_pmu_irqs_lock) --> lock(cpu_hotplug_lock) This locking order happens when dmc620_pmu_get_irq() is called from dmc620_pmu_device_probe(). Fix this possible deadlock scenario by reversing the locking order. Also export __cpuhp_state_add_instance_cpuslocked() so that it can be accessed by kernel modules. Signed-off-by: Waiman Long --- drivers/perf/arm_dmc620_pmu.c | 4 +++- kernel/cpu.c | 1 + 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c index 54aa4658fb36..78d3bfbe96a6 100644 --- a/drivers/perf/arm_dmc620_pmu.c +++ b/drivers/perf/arm_dmc620_pmu.c @@ -425,7 +425,7 @@ static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int = irq_num) if (ret) goto out_free_irq; =20 - ret =3D cpuhp_state_add_instance_nocalls(cpuhp_state_num, &irq->node); + ret =3D cpuhp_state_add_instance_nocalls_cpuslocked(cpuhp_state_num, &irq= ->node); if (ret) goto out_free_irq; =20 @@ -445,9 +445,11 @@ static int dmc620_pmu_get_irq(struct dmc620_pmu *dmc62= 0_pmu, int irq_num) { struct dmc620_pmu_irq *irq; =20 + cpus_read_lock(); mutex_lock(&dmc620_pmu_irqs_lock); irq =3D __dmc620_pmu_get_irq(irq_num); mutex_unlock(&dmc620_pmu_irqs_lock); + cpus_read_unlock(); =20 if (IS_ERR(irq)) return PTR_ERR(irq); diff --git a/kernel/cpu.c b/kernel/cpu.c index 6c0a92ca6bb5..05daaef362e6 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2036,6 +2036,7 @@ int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_= state state, mutex_unlock(&cpuhp_state_mutex); return ret; } +EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance_cpuslocked); =20 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *= node, bool invoke) --=20 2.31.1