Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751544AbbKIFmB (ORCPT ); Mon, 9 Nov 2015 00:42:01 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:36851 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbbKIFl7 (ORCPT ); Mon, 9 Nov 2015 00:41:59 -0500 Date: Mon, 9 Nov 2015 13:41:45 +0800 From: Peng Fan To: Will Deacon Cc: Peng Fan , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC] iommu: arm-smmu: correct reference count Message-ID: <20151109054143.GA5704@linux-jyl1.ap.freescale.net> References: <1446555557-3097-1-git-send-email-van.freenix@gmail.com> <20151103131734.GE14159@arm.com> <20151104024825.GA27479@shlinux2> <20151106122338.GI6087@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151106122338.GI6087@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2202 Lines: 56 Hi Will, On Fri, Nov 06, 2015 at 12:23:39PM +0000, Will Deacon wrote: >On Wed, Nov 04, 2015 at 10:48:28AM +0800, Peng Fan wrote: >> On Tue, Nov 03, 2015 at 01:17:34PM +0000, Will Deacon wrote: >> >On Tue, Nov 03, 2015 at 08:59:17PM +0800, Peng Fan wrote: >> >> iommu_group_alloc will initialize the reference count for group to 1. >> >> iommu_group_add_device also increase the group reference count, >> >> if nothing bad happends. And we need to add iommu_group_put to >> >> decrease the reference count for group. >> >> >> >> Signed-off-by: Peng Fan >> >> Cc: Will Deacon >> >> Cc: Joerg Roedel >> >> --- >> >> >> >> Not sure whether my understanding is correct or not. I checked rockchip-iommu.c >> >> exynos-iommu.c and fsl_pamu_domain.c, and they all have iommu_group_put after >> >> iommu_group_add_device. >> > >> >Doesn't this pair up with the iommu_group_remove_device in >> >arm_smmu_remove_device? Are you actually seeing an issue in practice? >> >> In arm_smmu_add_platform_device, >> iommu_group_alloc --> group->device_kobj ref count will be init to 1. >> iommu_group_add_device --> group->device_kobj ref count will be added 1 to 2. >> >> In arm_smmu_remove_device: >> iommu_group_remove_device --> Decrease group->device_kobj ref count by 1. >> After arm_smmu_remove_device, the ref count of group->device_kobj is not 0. >> >> So I think need to add iommu_group_put after iommu_group_add_device. >> If I am wrong, please correct me. > >Ok, I see what you're saying. iommu_group_get_for_dev has exactly the >same issue, so could you update arm-smmu-v3.c as well, please? I did not see the update about device_group for iommu, when I worked out this patch. Rebased to latest linux/master, whether to arm-smmu.c or arm-smmu-v3.c, only add 'iommu_group_put' at the end of iommu_group_get_for_dev is ok as the following. I'll send out V2. Thanks, Peng. > >Thanks, > >Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/