Altix supports "posted DMA", so that DMA may complete out of order. In some cases it's necessary for a driver to ensure that in-flight DMA has been flushed to memory for correct operation.
In particular this can be a problem with Infiniband, where writes to Completion Queues can race with DMA of data. The following patchset addresses this problem by allowing a memory region to be mapped with a "barrier" attribute. (On Altix, writes to memory regions with the barrier attribute have the side effect that in-flight DMA gets flushed to host memory.) There are three patches in this set: [1/3] dma: introduce no-op stub "dma_flags_set_dmaflush" [2/3] dma: override "dma_flags_set_dmaflush" for sn-ia64 [3/3] dma: use dma_flags_set_dmaflush in ib_umem_get (mthca only, for now) -- Arthur - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/