Why DMA and Cache Can Make Data Inconsistent
One of the most confusing driver bugs is “the data is clearly in memory, but the other side cannot see it.”
The CPU prepares a transmit buffer, but the network device sends old data. DMA has written received data into memory, but the driver or application still reads stale values. Adding logs makes the issue disappear; changing optimization brings it back.
These bugs are often not because DMA failed or the pointer is wrong. The problem is that CPU cache, DMA device, and memory visibility were not handled correctly.
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