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Date: Wed, 4 Nov 2015 10:48:28 +0800 From: Peng Fan <b51431@...escale.com> To: Will Deacon <will.deacon@....com> CC: Peng Fan <van.freenix@...il.com>, <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org> Subject: Re: [RFC] iommu: arm-smmu: correct reference count Hi Will, 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 <van.freenix@...il.com> >> Cc: Will Deacon <will.deacon@....com> >> Cc: Joerg Roedel <joro@...tes.org> >> --- >> >> 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. Just code inspection, not have a platform to test this. Regards, Peng. > >Will >_______________________________________________ >iommu mailing list >iommu@...ts.linux-foundation.org >https://lists.linuxfoundation.org/mailman/listinfo/iommu -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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