alloc_pdir() is called from smmu_iommu_domain_init() with spin_lock held. memory allocations in alloc_pdir() had to be atomic. Instead of converting into atomic allocation, this patch once releases a lock, does the allocation, holds the lock again and then sees if it's raced or not in order to avoid introducing mutex and preallocation.
Signed-off-by: Hiroshi DOYU <[email protected]> Reported-by: Chris Wright <[email protected]> Cc: Chris Wright <[email protected]> Acked-by: Stephen Warren <[email protected]> --- drivers/iommu/tegra-smmu.c | 77 +++++++++++++++++++++++++------------------ 1 files changed, 45 insertions(+), 32 deletions(-) diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c index 532c8a4..dbba94c 100644 --- a/drivers/iommu/tegra-smmu.c +++ b/drivers/iommu/tegra-smmu.c @@ -539,28 +539,39 @@ static inline void put_signature(struct smmu_as *as, /* * Caller must lock/unlock as */ -static int alloc_pdir(struct smmu_as *as) +static int alloc_pdir(struct smmu_as *as, unsigned long *flags) { unsigned long *pdir; - int pdn; + int pdn, err = 0; u32 val; struct smmu_device *smmu = as->smmu; + struct page *page; + unsigned int *cnt; - as->pte_count = devm_kzalloc(smmu->dev, - sizeof(as->pte_count[0]) * SMMU_PDIR_COUNT, GFP_KERNEL); - if (!as->pte_count) { - dev_err(smmu->dev, - "failed to allocate smmu_device PTE cunters\n"); - return -ENOMEM; + /* + * do the allocation outside the as lock + */ + spin_unlock_irqrestore(&as->lock, *flags); + cnt = devm_kzalloc(smmu->dev, + sizeof(cnt[0]) * SMMU_PDIR_COUNT, GFP_KERNEL); + page = alloc_page(GFP_KERNEL | __GFP_DMA); + spin_lock_irqsave(&as->lock, *flags); + + if (as->pdir_page) { + /* We raced, free the redundant */ + err = -EAGAIN; + goto err_out; } - as->pdir_page = alloc_page(GFP_KERNEL | __GFP_DMA); - if (!as->pdir_page) { - dev_err(smmu->dev, - "failed to allocate smmu_device page directory\n"); - devm_kfree(smmu->dev, as->pte_count); - as->pte_count = NULL; - return -ENOMEM; + + if (!page || !cnt) { + dev_err(smmu->dev, "failed to allocate at %s\n", __func__); + err = -ENOMEM; + goto err_out; } + + as->pdir_page = page; + as->pte_count = cnt; + SetPageReserved(as->pdir_page); pdir = page_address(as->pdir_page); @@ -577,6 +588,12 @@ static int alloc_pdir(struct smmu_as *as) FLUSH_SMMU_REGS(as->smmu); return 0; + +err_out: + devm_kfree(smmu->dev, cnt); + if (page) + __free_page(page); + return err; } static void __smmu_iommu_unmap(struct smmu_as *as, dma_addr_t iova) @@ -768,29 +785,29 @@ out: static int smmu_iommu_domain_init(struct iommu_domain *domain) { - int i; + int i, err = -ENODEV; unsigned long flags; struct smmu_as *as; struct smmu_device *smmu = smmu_handle; /* Look for a free AS with lock held */ for (i = 0; i < smmu->num_as; i++) { - struct smmu_as *tmp = &smmu->as[i]; - - spin_lock_irqsave(&tmp->lock, flags); - if (!tmp->pdir_page) { - as = tmp; - goto found; + as = &smmu->as[i]; + spin_lock_irqsave(&as->lock, flags); + if (!as->pdir_page) { + err = alloc_pdir(as, &flags); + if (!err) + goto found; } - spin_unlock_irqrestore(&tmp->lock, flags); + spin_unlock_irqrestore(&as->lock, flags); + if (err != -EAGAIN) + break; } - dev_err(smmu->dev, "no free AS\n"); - return -ENODEV; + if (i == smmu->num_as) + dev_err(smmu->dev, "no free AS\n"); + return err; found: - if (alloc_pdir(as) < 0) - goto err_alloc_pdir; - spin_lock(&smmu->lock); /* Update PDIR register */ @@ -806,10 +823,6 @@ found: dev_dbg(smmu->dev, "smmu_as@%p\n", as); return 0; - -err_alloc_pdir: - spin_unlock_irqrestore(&as->lock, flags); - return -ENODEV; } static void smmu_iommu_domain_destroy(struct iommu_domain *domain) -- 1.7.5.4 _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
