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From: Chris Friesen on 30 Jul 2010 14:50
Documentation/DMA-API-HOWTO.txt says that memory barriers are still
required when accessing consistent mappings. The example they give is
for reordering stores to consistent memory but I assume this also
applies to reordering loads.
However, I see many net drivers accessing the descriptor ring (in
consistent memory), checking the status bit for the buffer, then calling
dma_unmap_single() and accessing the data without any explicit memory
barrier. Does the unmapping call act as a barrier in this case?
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