On 6/22/18 10:38 AM, Stanimir Varbanov wrote:
Before entering into the read function we already hold a mutex which
serializes data reading so I cannot imagine how below sequence could
happen. Can you explain how to reproduce this race?
1. Core 1 reads status register, shows data is available.
2. Core 2 also reads status register, same result
3. Core 2 reads data register, depleting all entropy
4. Core 1 reads data register, which returns 0
I have a test which spawns 100 copies of rngtest on a 48-core machine.
Without the spinlock, the driver returns no data much more often.
If there really is a mutex that serializes data reads across all cores,
then I don't have an explanation.
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