This is used to protect potential race condition at use_count. since probes of client drivers, calling attach_dev(), may run concurrently. Signed-off-by: Nicolin Chen <nicoleotsuka@xxxxxxxxx> --- Changelog v1->v2: * N/A drivers/iommu/tegra-smmu.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c index ec4c9dafff95..acda5902e095 100644 --- a/drivers/iommu/tegra-smmu.c +++ b/drivers/iommu/tegra-smmu.c @@ -256,26 +256,19 @@ static int tegra_smmu_alloc_asid(struct tegra_smmu *smmu, unsigned int *idp) { unsigned long id; - mutex_lock(&smmu->lock); - id = find_first_zero_bit(smmu->asids, smmu->soc->num_asids); - if (id >= smmu->soc->num_asids) { - mutex_unlock(&smmu->lock); + if (id >= smmu->soc->num_asids) return -ENOSPC; - } set_bit(id, smmu->asids); *idp = id; - mutex_unlock(&smmu->lock); return 0; } static void tegra_smmu_free_asid(struct tegra_smmu *smmu, unsigned int id) { - mutex_lock(&smmu->lock); clear_bit(id, smmu->asids); - mutex_unlock(&smmu->lock); } static bool tegra_smmu_capable(enum iommu_cap cap) @@ -420,17 +413,21 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu, struct tegra_smmu_as *as) { u32 value; - int err; + int err = 0; + + mutex_lock(&smmu->lock); if (as->use_count > 0) { as->use_count++; - return 0; + goto err_unlock; } as->pd_dma = dma_map_page(smmu->dev, as->pd, 0, SMMU_SIZE_PD, DMA_TO_DEVICE); - if (dma_mapping_error(smmu->dev, as->pd_dma)) - return -ENOMEM; + if (dma_mapping_error(smmu->dev, as->pd_dma)) { + err = -ENOMEM; + goto err_unlock; + } /* We can't handle 64-bit DMA addresses */ if (!smmu_dma_addr_valid(smmu, as->pd_dma)) { @@ -453,24 +450,35 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu, as->smmu = smmu; as->use_count++; + mutex_unlock(&smmu->lock); + return 0; err_unmap: dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE); +err_unlock: + mutex_unlock(&smmu->lock); + return err; } static void tegra_smmu_as_unprepare(struct tegra_smmu *smmu, struct tegra_smmu_as *as) { - if (--as->use_count > 0) + mutex_lock(&smmu->lock); + + if (--as->use_count > 0) { + mutex_unlock(&smmu->lock); return; + } tegra_smmu_free_asid(smmu, as->id); dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE); as->smmu = NULL; + + mutex_unlock(&smmu->lock); } static int tegra_smmu_attach_dev(struct iommu_domain *domain, -- 2.17.1