From nobody Thu Sep 11 19:21:03 2025 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 00E2BC001B0 for ; Mon, 7 Aug 2023 15:46:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229645AbjHGPq3 (ORCPT ); Mon, 7 Aug 2023 11:46:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229500AbjHGPq2 (ORCPT ); Mon, 7 Aug 2023 11:46:28 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 617EE212E for ; Mon, 7 Aug 2023 08:45:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691423105; 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=7w4UuYP3MJszw+7GPKE+QIfdQPV+qBZTD63Uc3XzFSQ=; b=fzKwL2p4bD+RlKHoAxPcgicvpUbsPCKneCJsTlrHY/NCaBXbYEVPdB8KnLKqjMtEb2AxzP nhTbO+GYHr7m0lTc+YZqffNHMyv+we/eImFuvxA1HeRntB5SU8K6yu9ePds9hMnaa/hGqy XYsPwG2YOzpRQtrWAak2mR1aOy+KalM= Received: from mimecast-mx02.redhat.com (66.187.233.73 [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-653-zlU_T_61PsaDCEfqc8eR-Q-1; Mon, 07 Aug 2023 11:45:00 -0400 X-MC-Unique: zlU_T_61PsaDCEfqc8eR-Q-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 21DDA3811F2C; Mon, 7 Aug 2023 15:44:59 +0000 (UTC) Received: from llong.com (unknown [10.22.17.157]) by smtp.corp.redhat.com (Postfix) with ESMTP id 028472026D4B; Mon, 7 Aug 2023 15:44:57 +0000 (UTC) From: Waiman Long To: Will Deacon , Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Robin Murphy , Waiman Long Subject: [PATCH v4] perf/arm-dmc620: Fix dmc620_pmu_irqs_lock/cpu_hotplug_lock circular lock dependency Date: Mon, 7 Aug 2023 11:44:46 -0400 Message-Id: <20230807154446.208572-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 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() calls cpuhp_state_add_instance_nocalls(). Since dmc620_pmu_irqs_lock is used for protecting the dmc620_pmu_irqs structure only, we don't actually need to hold the lock when adding a new instance to the CPU hotplug subsystem. Fix this possible deadlock scenario by adding a new dmc620_pmu_get_irq_lock for protecting the call to __dmc620_pmu_get_irq() and taking dmc620_pmu_irqs_lock inside __dmc620_pmu_get_irq() only when dmc620_pmu_irqs is being searched or modified. As a result, cpuhp_state_add_instance_nocalls() won't be called with dmc620_pmu_irqs_lock held and cpu_hotplug_lock won't be acquired after dmc620_pmu_irqs_lock. Suggested-by: Robin Murphy Signed-off-by: Waiman Long --- drivers/perf/arm_dmc620_pmu.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c index 9d0f01c4455a..895971915f2d 100644 --- a/drivers/perf/arm_dmc620_pmu.c +++ b/drivers/perf/arm_dmc620_pmu.c @@ -68,6 +68,7 @@ =20 static LIST_HEAD(dmc620_pmu_irqs); static DEFINE_MUTEX(dmc620_pmu_irqs_lock); +static DEFINE_MUTEX(dmc620_pmu_get_irq_lock); =20 struct dmc620_pmu_irq { struct hlist_node node; @@ -421,11 +422,18 @@ static irqreturn_t dmc620_pmu_handle_irq(int irq_num,= void *data) static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int irq_num) { struct dmc620_pmu_irq *irq; + bool found =3D false; int ret; =20 + mutex_lock(&dmc620_pmu_irqs_lock); list_for_each_entry(irq, &dmc620_pmu_irqs, irqs_node) - if (irq->irq_num =3D=3D irq_num && refcount_inc_not_zero(&irq->refcount)) - return irq; + if (irq->irq_num =3D=3D irq_num && refcount_inc_not_zero(&irq->refcount)= ) { + found =3D true; + break; + } + mutex_unlock(&dmc620_pmu_irqs_lock); + if (found) + return irq; =20 irq =3D kzalloc(sizeof(*irq), GFP_KERNEL); if (!irq) @@ -452,7 +460,9 @@ static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int = irq_num) goto out_free_irq; =20 irq->irq_num =3D irq_num; + mutex_lock(&dmc620_pmu_irqs_lock); list_add(&irq->irqs_node, &dmc620_pmu_irqs); + mutex_unlock(&dmc620_pmu_irqs_lock); =20 return irq; =20 @@ -467,9 +477,9 @@ static int dmc620_pmu_get_irq(struct dmc620_pmu *dmc620= _pmu, int irq_num) { struct dmc620_pmu_irq *irq; =20 - mutex_lock(&dmc620_pmu_irqs_lock); + mutex_lock(&dmc620_pmu_get_irq_lock); irq =3D __dmc620_pmu_get_irq(irq_num); - mutex_unlock(&dmc620_pmu_irqs_lock); + mutex_unlock(&dmc620_pmu_get_irq_lock); =20 if (IS_ERR(irq)) return PTR_ERR(irq); --=20 2.31.1