From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 903C93630A0 for ; Tue, 9 Jun 2026 18:03:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781028214; cv=none; b=ZGJrZ/4+wyZiyeFdHB4rzW51/j9WXn86dKp7aC6iQ1xGmmYSnBgwdxrVMa2RpgQZZgj+Cx1fU00LYw5WPJtZ4Wo34WM63UeCAhsblw4l5Xpe3PaZ76owJDbvld1POv7iUeZIcsdkf7aunI2g62Xr84rdpMiUx6xBZJ4p6A7yNA8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781028214; c=relaxed/simple; bh=Q65ug760ZPb/OlYGqOGNlVJO+R74CPaBf2rOMM9K0rA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DswcKDp/hnYWnauKhEErQdUHovfrcZxOSVW6h3YmMpG+LL8W4ZBosUPYHrdymuoUTV9faYLqV/Bcxu8179O9LKPK+oZa3ptDvJfGSW3D8pmRrR4Gw04RaoYQtzB9KZ8EIO9S955dCfTPk4V4p8L66TyQgGdDG0RcWrRiCm7bJEU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=YmgITDhC; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YmgITDhC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1781028212; 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: in-reply-to:in-reply-to:references:references; bh=bba3ShkPXLnJs6fxJeKo/039rEsBR36+Fx7OF6O65d4=; b=YmgITDhCXCI2AtsaOkw7DV+2LAQ0dGFsglMkZQIFvniJeBFGEFCfA8z42S7OiRrpnnDqZb g6TGQ0PSSSD4X7o4KT6s0B3GUjfjvs+k2HK+5p7q1mSqZJb+DRyMtJF2P5KUVW3nGM1QRh 6JtlJc6MQaWXm6/MJTuCfTnWGwxvYmU= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-690-uwoDDCC3PHSB1WBo60-8WQ-1; Tue, 09 Jun 2026 14:03:29 -0400 X-MC-Unique: uwoDDCC3PHSB1WBo60-8WQ-1 X-Mimecast-MFC-AGG-ID: uwoDDCC3PHSB1WBo60-8WQ_1781028208 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D2F7C180131A; Tue, 9 Jun 2026 18:03:27 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.65.187]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 6345A18005B8; Tue, 9 Jun 2026 18:03:26 +0000 (UTC) From: Waiman Long To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Frederic Weisbecker , Danilo Krummrich , Tejun Heo , Jinhui Guo , Waiman Long Subject: [PATCH v4 1/2] PCI: Suppress false positive lockdep warning in pci_call_probe() Date: Tue, 9 Jun 2026 14:03:14 -0400 Message-ID: <20260609180315.850637-2-longman@redhat.com> In-Reply-To: <20260609180315.850637-1-longman@redhat.com> References: <20260609180315.850637-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 local_pci_probe() and hence pci_call_probe() can be called recursively, e.g. when vmd_probe() calls .probe() for devices in the new hierarchy below VMD or a PF .probe() enables VFs and calls .probe() for them. If the recursive calls are done indirectly via workqueue kworker, a lockdep recursive warning like the following can be produced. ============================================ WARNING: possible recursive locking detected 7.1.0-rc6-test+ #1 Not tainted -------------------------------------------- kworker/52:1/1593 is trying to acquire lock: ffffc9001498f708 ((work_completion)(&arg.work)){+.+.}-{0:0}, at: start_flush_work+0x3e9/0x9a0 but task is already holding lock: ffffc9001498fd10 ((work_completion)(&arg.work)){+.+.}-{0:0}, at: process_one_work+0xd4c/0x1390 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock((work_completion)(&arg.work)); lock((work_completion)(&arg.work)); *** DEADLOCK *** This is a false positive warning due to the limitation on the number of distinct lockdep keys allowed. The same lockdep key is used when the INIT_WORK_ONSTACK() macro is called in pci_call_probe(). So when a work function queued by pci_call_probe() calls into pci_call_probe() again and another work function is queued and flushed, the lockdep warning will be displayed. This can be suppressed by registering a dynamic key and used it whenever the current task is a wq kworker. Dynamic lockdep keys are limited finite resources and they should be used only when really necessary. Signed-off-by: Waiman Long --- drivers/pci/pci-driver.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index e3f59001785a..bc8c0f061072 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -394,8 +394,21 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev, error = local_pci_probe(&ddi); } else { struct pci_probe_arg arg = { .ddi = &ddi }; + struct lock_class_key key; + + /* + * A nested pci_call_probe() via a work func will produce a + * false positive lockdep recursive locking warning. Use + * lockdep_register_key() to provision a dynamic key to + * suppress this warning when the current task is a wq kworker. + */ + if (current->flags & PF_WQ_WORKER) { + lockdep_register_key(&key); + INIT_WORK_ONSTACK_KEY(&arg.work, local_pci_probe_callback, &key); + } else { + INIT_WORK_ONSTACK(&arg.work, local_pci_probe_callback); + } - INIT_WORK_ONSTACK(&arg.work, local_pci_probe_callback); /* * The target election and the enqueue of the work must be within * the same RCU read side section so that when the workqueue pool @@ -422,6 +435,8 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev, } destroy_work_on_stack(&arg.work); + if (current->flags & PF_WQ_WORKER) + lockdep_unregister_key(&key); } dev->is_probed = 0; -- 2.54.0