From mboxrd@z Thu Jan 1 00:00:00 1970 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 366EDF34C45 for ; Fri, 24 Apr 2026 02:56:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=pTZmv4hKvATZEtLFq22XyF/LcSuQagnaf3weRPP0x+Y=; b=PI941qP+EQowpMhQn0+3HEgb4X p1KmxtPhJCPN/zsXuMB2w/WYamRFtJdWc0tdHp4zxsXmr1kOP9TAjZRt4BTQtclCeuB7nLBIOV6ux BDYLmJQVAVKxAuKCWBdU5QV/IneXrqZcMYyb0Vsairs2IViPwlSNjBRAgCOjyuThEmkA1f1nJKcA9 s2DM3fvYlmcAQ0biCkJxkWkHEFGggXX+M2eZQsRlue8MlDf3Nf7gNJvXVYeRpC8NexPJyXmB6YoEE VH71Nwa25BC5wHnbZEsEKBORu6Cy27BWndq2OlWHzVmxprg82Rz2vrl+0fJW/CPrzdim4zxrLZbsD bxTZ9+sg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wG6i2-0000000CXrs-32C3; Fri, 24 Apr 2026 02:56:02 +0000 Received: from mgamail.intel.com ([192.198.163.16]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wG6hz-0000000CXrG-2av7 for linux-arm-kernel@lists.infradead.org; Fri, 24 Apr 2026 02:56:00 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1776999360; x=1808535360; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=pZDuDeaZoj7O1LubWx5vw5Buq2BjiWMeU3DeyutW5QQ=; b=ei1IdjMOG3K9HZwsZ4WRAK3a6PKnD3pRkCgjdI/khQhF5uqPnsoLnHsR RkuPmGVebjAfHsUSPtvg7fzapsbw30FBgfR9HfEVYV8/cZk4liW5nZgxV jW9ZNZEO0FeLY3Z7inYSyvNHWVc/h6iEhr2VD2t36ia3Gg91ptu7KOmVI 2jNjBWnw751idLyAGcMMwxr0JNAwkMvXb34hDfUoiprBOSKrjAN1BP6AV UsSNjmg97WCBmPnWiKXaJKApC2OHqnDz3RS0vnLEO/9TfPXmIXIhi3/eG 9hMGJtexQFZH13sTx7hVMGRrtxz2dt9ywmvMciiEFVsDmBSHEzZmZQXYs A==; X-CSE-ConnectionGUID: lgW6hdKpTgu04ZaovZRTFg== X-CSE-MsgGUID: ttrG/bm3QhGd3bL9zVPDKQ== X-IronPort-AV: E=McAfee;i="6800,10657,11765"; a="65511059" X-IronPort-AV: E=Sophos;i="6.23,195,1770624000"; d="scan'208";a="65511059" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Apr 2026 19:55:59 -0700 X-CSE-ConnectionGUID: uP9vfrh5TES/laj0y+LAEg== X-CSE-MsgGUID: 2db0jdZfQsqaiY8zHzQvsA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,195,1770624000"; d="scan'208";a="237184547" Received: from allen-sbox.sh.intel.com (HELO [10.239.159.30]) ([10.239.159.30]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Apr 2026 19:55:55 -0700 Message-ID: <779dad61-d7e7-4ae0-83a9-8c5920222219@linux.intel.com> Date: Fri, 24 Apr 2026 10:53:49 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 05/11] iommu: Change group->devices to RCU-protected list To: Nicolin Chen , Will Deacon , Robin Murphy , Joerg Roedel , Bjorn Helgaas , Jason Gunthorpe Cc: "Rafael J . Wysocki" , Len Brown , Pranjal Shrivastava , Mostafa Saleh , Kevin Tian , linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, vsethi@nvidia.com, Shuai Xue References: <12a224061de4fff9e0725909fd0ba4e14996ff08.1776381841.git.nicolinc@nvidia.com> Content-Language: en-US From: Baolu Lu In-Reply-To: <12a224061de4fff9e0725909fd0ba4e14996ff08.1776381841.git.nicolinc@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260423_195559_729479_7E49BFE4 X-CRM114-Status: GOOD ( 13.05 ) 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 On 4/17/26 07:28, Nicolin Chen wrote: > To allow lockless iterations of the group->devices list in an ISR context > that cannot hold the group->mutex, change the list to be RCU protected. > > Signed-off-by: Nicolin Chen > --- > drivers/iommu/iommu.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 768ac728b4cc3..d1be62a07904a 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -84,18 +84,20 @@ struct group_device { > */ > bool blocked; > unsigned int reset_depth; > + struct rcu_head rcu; > }; > > /* Iterate over each struct group_device in a struct iommu_group */ > #define for_each_group_device(group, pos) \ > - list_for_each_entry(pos, &(group)->devices, list) > + list_for_each_entry_rcu(pos, &(group)->devices, list, \ > + lockdep_is_held(&(group)->mutex)) for_each_group_device() is used in bus_iommu_probe() without holding either the mutex or the rcu lock: static int bus_iommu_probe(const struct bus_type *bus) { struct iommu_group *group, *next; LIST_HEAD(group_list); int ret; [-- cut for short --] mutex_unlock(&group->mutex); /* * FIXME: Mis-locked because the ops->probe_finalize() call-back * of some IOMMU drivers calls arm_iommu_attach_device() which * in-turn might call back into IOMMU core code, where it tries * to take group->mutex, resulting in a deadlock. */ for_each_group_device(group, gdev) iommu_group_do_probe_finalize(gdev->dev); } return 0; } Will the change above trigger a lockdep splat due to this "mis-locked" case?" Thanks, baolu