From nobody Fri Sep 12 07:29:13 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 81262C001E0 for ; Thu, 10 Aug 2023 15:42:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236186AbjHJPmO (ORCPT ); Thu, 10 Aug 2023 11:42:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233659AbjHJPmM (ORCPT ); Thu, 10 Aug 2023 11:42:12 -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 8D57A2705 for ; Thu, 10 Aug 2023 08:41:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691682085; 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=atSIShNb1k5EouTCC7gYCjFuXMvvzMrZitLjweZI368=; b=LelDGHSVtkS5s2qK7y7AvYpWMPbmNyvCiqyrPM62d77O6z+N0Y5VE5CCfMht4JlI9Dc6P+ NpkcsaGX8Vozi4JeYydpkT5TtrmQXx86NOMDGEnn0P9+0kTit4uc4lHevTrfPvgGt0LcXF iPoA1zErY1ye1z7JQNWfRLkPeRKgWu0= 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-320-qUnfye_xObiUAg9FNFPnAg-1; Thu, 10 Aug 2023 11:41:24 -0400 X-MC-Unique: qUnfye_xObiUAg9FNFPnAg-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 6AFCB381C16D; Thu, 10 Aug 2023 15:41:22 +0000 (UTC) Received: from llong.com (unknown [10.22.18.33]) by smtp.corp.redhat.com (Postfix) with ESMTP id F33B72026D4B; Thu, 10 Aug 2023 15:41:21 +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 v5] perf/arm-dmc620: Fix dmc620_pmu_irqs_lock/cpu_hotplug_lock circular lock dependency Date: Thu, 10 Aug 2023 11:41:14 -0400 Message-Id: <20230810154114.405742-1-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, 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_lock for protecting the call to __dmc620_pmu_get_irq(). While at it, rename dmc620_pmu_irqs_lock to dmc620_pmu_list_lock as it is now just protecting the iteration and modification of pmus_node and irqs_node lists. As a result, cpuhp_state_add_instance_nocalls() won't be called with reanemd dmc620_pmu_list_lock held and cpu_hotplug_lock won't be acquired after dmc620_pmu_list_lock. Suggested-by: Robin Murphy Signed-off-by: Waiman Long --- drivers/perf/arm_dmc620_pmu.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c index 9d0f01c4455a..a5bfc8f2e6ab 100644 --- a/drivers/perf/arm_dmc620_pmu.c +++ b/drivers/perf/arm_dmc620_pmu.c @@ -66,8 +66,14 @@ #define DMC620_PMU_COUNTERn_OFFSET(n) \ (DMC620_PMU_COUNTERS_BASE + 0x28 * (n)) =20 +/* + * The allowable lock ordering is: + * - dmc620_pmu_get_lock (protects call to __dmc620_pmu_get_irq()) + * - dmc620_pmu_list_lock (protects pmus_node & irqs_node lists) + */ +static DEFINE_MUTEX(dmc620_pmu_get_lock); +static DEFINE_MUTEX(dmc620_pmu_list_lock); static LIST_HEAD(dmc620_pmu_irqs); -static DEFINE_MUTEX(dmc620_pmu_irqs_lock); =20 struct dmc620_pmu_irq { struct hlist_node node; @@ -423,9 +429,11 @@ static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int= irq_num) struct dmc620_pmu_irq *irq; int ret; =20 + mutex_lock(&dmc620_pmu_list_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; + goto unlock_out; + mutex_unlock(&dmc620_pmu_list_lock); =20 irq =3D kzalloc(sizeof(*irq), GFP_KERNEL); if (!irq) @@ -452,8 +460,10 @@ 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_list_lock); list_add(&irq->irqs_node, &dmc620_pmu_irqs); - +unlock_out: + mutex_unlock(&dmc620_pmu_list_lock); return irq; =20 out_free_irq: @@ -467,17 +477,17 @@ static int dmc620_pmu_get_irq(struct dmc620_pmu *dmc6= 20_pmu, int irq_num) { struct dmc620_pmu_irq *irq; =20 - mutex_lock(&dmc620_pmu_irqs_lock); + mutex_lock(&dmc620_pmu_get_lock); irq =3D __dmc620_pmu_get_irq(irq_num); - mutex_unlock(&dmc620_pmu_irqs_lock); + mutex_unlock(&dmc620_pmu_get_lock); =20 if (IS_ERR(irq)) return PTR_ERR(irq); =20 dmc620_pmu->irq =3D irq; - mutex_lock(&dmc620_pmu_irqs_lock); + mutex_lock(&dmc620_pmu_list_lock); list_add_rcu(&dmc620_pmu->pmus_node, &irq->pmus_node); - mutex_unlock(&dmc620_pmu_irqs_lock); + mutex_unlock(&dmc620_pmu_list_lock); =20 return 0; } @@ -486,16 +496,16 @@ static void dmc620_pmu_put_irq(struct dmc620_pmu *dmc= 620_pmu) { struct dmc620_pmu_irq *irq =3D dmc620_pmu->irq; =20 - mutex_lock(&dmc620_pmu_irqs_lock); + mutex_lock(&dmc620_pmu_list_lock); list_del_rcu(&dmc620_pmu->pmus_node); =20 if (!refcount_dec_and_test(&irq->refcount)) { - mutex_unlock(&dmc620_pmu_irqs_lock); + mutex_unlock(&dmc620_pmu_list_lock); return; } =20 list_del(&irq->irqs_node); - mutex_unlock(&dmc620_pmu_irqs_lock); + mutex_unlock(&dmc620_pmu_list_lock); =20 free_irq(irq->irq_num, irq); cpuhp_state_remove_instance_nocalls(cpuhp_state_num, &irq->node); @@ -638,10 +648,10 @@ static int dmc620_pmu_cpu_teardown(unsigned int cpu, return 0; =20 /* We're only reading, but this isn't the place to be involving RCU */ - mutex_lock(&dmc620_pmu_irqs_lock); + mutex_lock(&dmc620_pmu_list_lock); list_for_each_entry(dmc620_pmu, &irq->pmus_node, pmus_node) perf_pmu_migrate_context(&dmc620_pmu->pmu, irq->cpu, target); - mutex_unlock(&dmc620_pmu_irqs_lock); + mutex_unlock(&dmc620_pmu_list_lock); =20 WARN_ON(irq_set_affinity(irq->irq_num, cpumask_of(target))); irq->cpu =3D target; --=20 2.31.1