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iommu/tegra-smmu: Balance IOMMU group reference count

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For groups that are shared between multiple devices, care must be taken
to acquire a reference for each device, otherwise the IOMMU core ends up
dropping the last reference too early, which will cause the group to be
released while consumers may still be thinking that they're holding a
reference to it.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20200806155404.3936074-3-thierry.reding@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Thierry Reding 2020-08-06 17:54:03 +02:00 • committed by Joerg Roedel
parent 002957020e
commit 5b30fbfa2a
1 changed files with 3 additions and 1 deletions
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4
drivers/iommu/tegra-smmu.c
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@ -818,6 +818,7 @@ static struct iommu_group *tegra_smmu_group_get(struct tegra_smmu *smmu,
{
const struct tegra_smmu_group_soc *soc;
struct tegra_smmu_group *group;
struct iommu_group *grp;
soc = tegra_smmu_find_group(smmu, swgroup);
if (!soc)
@ -827,8 +828,9 @@ static struct iommu_group *tegra_smmu_group_get(struct tegra_smmu *smmu,
list_for_each_entry(group, &smmu->groups, list)
if (group->soc == soc) {
grp = iommu_group_ref_get(group->group);
mutex_unlock(&smmu->lock);
return group->group;
return grp;
}
group = devm_kzalloc(smmu->dev, sizeof(*group), GFP_KERNEL);