| Message ID | 20200928235901.28337-3-nicoleotsuka@gmail.com |
|---|---|
| State | Deferred |
| Headers | show |
| Series | iommu/tegra-smmu: Two followup changes | expand |
... > 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; This looks a bit odd because it's not a error condition. Perhaps should be better to "goto bump_usecount"? Or make it similar to tegra_smmu_as_unprepare()? > } > > 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; bump_usecount: > 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, >
On Tue, Sep 29, 2020 at 03:17:58AM +0300, Dmitry Osipenko wrote: > ... > > 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; > > This looks a bit odd because it's not a error condition. Perhaps should > be better to "goto bump_usecount"? > > Or make it similar to tegra_smmu_as_unprepare()? Hmm...I think it's simple to just make it "goto unlock" then.
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,
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@gmail.com> --- Changelog v1->v2: * N/A drivers/iommu/tegra-smmu.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-)