From: David Brownell On at least ARM (and I'm told MIPS too) dma_free_coherent() has a newish call context requirement: unlike its dma_alloc_coherent() sibling, it may not be called with IRQs disabled. (This was new behavior on ARM as of late 2005, caused by ARM SMP updates.) This little surprise can be annoyingly driver-visible. Since it looks like that restriction won't be removed, this patch changes the definition of the API to include that requirement. Also, to help catch nonportable drivers, it updates the x86 and swiotlb versions to include the relevant warnings. (I already observed that it trips on the bus_reset_tasklet of the new firewire_ohci driver.) Signed-off-by: David Brownell Cc: David Miller Acked-by: Russell King Cc: Andi Kleen Signed-off-by: Andrew Morton --- Documentation/DMA-API.txt | 3 +++ arch/i386/kernel/pci-dma.c | 3 ++- arch/x86_64/kernel/pci-dma.c | 1 + lib/swiotlb.c | 1 + 4 files changed, 7 insertions(+), 1 deletion(-) diff -puN arch/i386/kernel/pci-dma.c~dma_free_coherent-needs-irqs-enabled-sigh arch/i386/kernel/pci-dma.c --- a/arch/i386/kernel/pci-dma.c~dma_free_coherent-needs-irqs-enabled-sigh +++ a/arch/i386/kernel/pci-dma.c @@ -62,7 +62,8 @@ void dma_free_coherent(struct device *de { struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL; int order = get_order(size); - + + WARN_ON(irqs_disabled()); /* for portability */ if (mem && vaddr >= mem->virt_base && vaddr < (mem->virt_base + (mem->size << PAGE_SHIFT))) { int page = (vaddr - mem->virt_base) >> PAGE_SHIFT; diff -puN arch/x86_64/kernel/pci-dma.c~dma_free_coherent-needs-irqs-enabled-sigh arch/x86_64/kernel/pci-dma.c --- a/arch/x86_64/kernel/pci-dma.c~dma_free_coherent-needs-irqs-enabled-sigh +++ a/arch/x86_64/kernel/pci-dma.c @@ -161,6 +161,7 @@ EXPORT_SYMBOL(dma_alloc_coherent); void dma_free_coherent(struct device *dev, size_t size, void *vaddr, dma_addr_t bus) { + WARN_ON(irqs_disabled()); /* for portability */ if (dma_ops->unmap_single) dma_ops->unmap_single(dev, bus, size, 0); free_pages((unsigned long)vaddr, get_order(size)); diff -puN Documentation/DMA-API.txt~dma_free_coherent-needs-irqs-enabled-sigh Documentation/DMA-API.txt --- a/Documentation/DMA-API.txt~dma_free_coherent-needs-irqs-enabled-sigh +++ a/Documentation/DMA-API.txt @@ -68,6 +68,9 @@ size and dma_handle must all be the same consistent allocate. cpu_addr must be the virtual address returned by the consistent allocate. +Note that unlike their sibling allocation calls, these routines +may only be called with IRQs enabled. + Part Ib - Using small dma-coherent buffers ------------------------------------------ diff -puN lib/swiotlb.c~dma_free_coherent-needs-irqs-enabled-sigh lib/swiotlb.c --- a/lib/swiotlb.c~dma_free_coherent-needs-irqs-enabled-sigh +++ a/lib/swiotlb.c @@ -497,6 +497,7 @@ void swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, dma_addr_t dma_handle) { + WARN_ON(irqs_disabled()); if (!(vaddr >= (void *)io_tlb_start && vaddr < (void *)io_tlb_end)) free_pages((unsigned long) vaddr, get_order(size)); _