On 08/06/2018 01:33 AM, Christoph Hellwig wrote:
On Sun, Aug 05, 2018 at 02:38:22PM -0700, Guenter Roeck wrote:AFAICS it used to be interrupt tolerant for all but x86 up to commit 6894258eda ("dma-mapping: consolidate dma_{alloc,free}_{attrs,coherent}"). A quick test shows that the warning is indeed not seen if I run my test on v3.18.y. You would have to ask Christoph why it is now interrupt-intolerant for all architectures.interrupt-tolerant actually is a very odd wording. x86 itself (at least unless using an iommu) actually is fine with calling dma_free_* with interrupts disabled, but many other architectures are not. For many architectures that are not cache coherent we'll have to manipulale the kernel page tables when freeing coherent memory, which we absolutely can't do from irq context. And as usual in the kernel we try to enforce the same rules on everyone to allow for portable code. Also except for the odd USB use cases that abuses dma_alloc_coherent for the bounce buffers in device local memory you are doing something wrong if you call dma_alloc*/dma_free* anywhere but during device initialization and removal. These are slow path interfaces for allocating memory for things like descriptors and similar. Your fast path should be using dma_map*/dma_unmap*.
FWIW, that isn't "my" code. I just had the impunity to test it. Cheers, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
