From patchwork Sat Jul 22 03:17:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 13322761 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D8156EB64DA for ; Sat, 22 Jul 2023 03:18:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=/ly/AKtC2bjEqOnTSrqn/vmbbPt5mmGQxCAWUQ782GY=; b=f/Ikje1BW3ZukZ pTHIhE2CjE/x3ji9fr9plcDfyYb78SFyNT9KAu8DgQ4vrKW2IlmXNt/P5WmXy+wU2YMGwuTH8XW2l USQ/zxG3i565BQKiAluK8JNpqqe+e92C2GLr/JVqoW8atmmG4+ZrN76dY1Z5gULwmALqhgXWOA0SN 60WtoRFOsL/XKtcUuQNtl5agkPI+x5lqjK3LstSt2/3d6lt0ZVhfmlh35db99ulTJpElucJA5zB+B buvntrPrcjf1ZpPsypwKGT6FJnzVwm1BpZAgG9PqLbXW0ERV6RkT/ozAgvGHAKIjuDt1gwA4LDha3 WfnXAWPnBGY9iwG1DURg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qN38A-00FhdN-1e; Sat, 22 Jul 2023 03:18:06 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qN382-00Fhca-1b for linux-arm-kernel@lists.infradead.org; Sat, 22 Jul 2023 03:18:02 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689995865; 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=0uW4VHgKV+Lqk0wGj2Kld/LW6LChZPKDcy+khsmFX/c=; b=OT13wA7rvxmZqpnTmlC2Jzd+w3w+7FPRnisHfqTC27QoNoPV8Bc6+gAWbZxlK5tAcXmnaK 3riOIKBHcPSNcT+OwjtiTCcBPsRodpoer6Dd1i8ST6DLNrsVmfUEHWk0fLtvC/ofsqAgvs t1SW0lxC0d0sNd8uavSS8Yjh1+VxlkU= 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-625-ds7PrvWIO_iOLDwToedKAA-1; Fri, 21 Jul 2023 23:17:40 -0400 X-MC-Unique: ds7PrvWIO_iOLDwToedKAA-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 24EBE3C0D183; Sat, 22 Jul 2023 03:17:40 +0000 (UTC) Received: from llong.com (unknown [10.22.16.21]) by smtp.corp.redhat.com (Postfix) with ESMTP id AEE77200A7CA; Sat, 22 Jul 2023 03:17:39 +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 v3] perf/arm-dmc620: Fix dmc620_pmu_irqs_lock/cpu_hotplug_lock circular lock dependency Date: Fri, 21 Jul 2023 23:17:28 -0400 Message-Id: <20230722031729.3913953-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230721_201758_631467_D2FE59BF X-CRM114-Status: GOOD ( 18.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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(). 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 releasing the lock before calling cpuhp_state_add_instance_nocalls() and reacquiring it afterward. To avoid the possibility of 2 racing dmc620_pmu_get_irq() calls inserting duplicated dmc620_pmu_irq structures with the same irq number, a dummy entry is inserted before releasing the lock which will block a competing thread from inserting another irq structure of the same irq number. Suggested-by: Robin Murphy Signed-off-by: Waiman Long --- drivers/perf/arm_dmc620_pmu.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c index 9d0f01c4455a..7cafd4dd4522 100644 --- a/drivers/perf/arm_dmc620_pmu.c +++ b/drivers/perf/arm_dmc620_pmu.c @@ -76,6 +76,7 @@ struct dmc620_pmu_irq { refcount_t refcount; unsigned int irq_num; unsigned int cpu; + unsigned int valid; }; struct dmc620_pmu { @@ -423,9 +424,14 @@ static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int irq_num) struct dmc620_pmu_irq *irq; int ret; - list_for_each_entry(irq, &dmc620_pmu_irqs, irqs_node) - if (irq->irq_num == irq_num && refcount_inc_not_zero(&irq->refcount)) + list_for_each_entry(irq, &dmc620_pmu_irqs, irqs_node) { + if (irq->irq_num != irq_num) + continue; + if (!irq->valid) + return ERR_PTR(-EAGAIN); /* Try again later */ + if (refcount_inc_not_zero(&irq->refcount)) return irq; + } irq = kzalloc(sizeof(*irq), GFP_KERNEL); if (!irq) @@ -447,13 +453,23 @@ static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int irq_num) if (ret) goto out_free_irq; - ret = cpuhp_state_add_instance_nocalls(cpuhp_state_num, &irq->node); - if (ret) - goto out_free_irq; - irq->irq_num = irq_num; list_add(&irq->irqs_node, &dmc620_pmu_irqs); + /* + * Release dmc620_pmu_irqs_lock before calling + * cpuhp_state_add_instance_nocalls() and reacquire it afterward. + */ + mutex_unlock(&dmc620_pmu_irqs_lock); + ret = cpuhp_state_add_instance_nocalls(cpuhp_state_num, &irq->node); + mutex_lock(&dmc620_pmu_irqs_lock); + + if (ret) { + list_del(&irq->irqs_node); + goto out_free_irq; + } + + irq->valid = true; return irq; out_free_irq: