From: Mike Waychison Date: Sat, 22 Apr 2006 09:36:06 +0000 (-0700) Subject: [PATCH] x86_64: Fix a race in the free_iommu path X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5b20192727ef2c047343a043ee4fbda67e2beef4;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git [PATCH] x86_64: Fix a race in the free_iommu path We do this by removing a micro-optimization that tries to avoid grabbing the iommu_bitmap_lock spinlock and using a bus-locked operation. This still races with other simultaneous alloc_iommu or free_iommu(size > 1) which both use bus-unlocked operations. The end result of this race is eventually ending up with an iommu_gart_bitmap that has bits errornously set all over, making large contiguous iommu space allocations fail with 'PCI-DMA: Out of IOMMU space'. Signed-off-by: Mike Waychison Signed-off-by: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c index a6c01e12126..9d3d76c85ae 100644 --- a/arch/x86_64/kernel/pci-gart.c +++ b/arch/x86_64/kernel/pci-gart.c @@ -112,10 +112,6 @@ static unsigned long alloc_iommu(int size) static void free_iommu(unsigned long offset, int size) { unsigned long flags; - if (size == 1) { - clear_bit(offset, iommu_gart_bitmap); - return; - } spin_lock_irqsave(&iommu_bitmap_lock, flags); __clear_bit_string(iommu_gart_bitmap, offset, size); spin_unlock_irqrestore(&iommu_bitmap_lock, flags);