Messages in this thread | | | Date | Thu, 10 Jun 2010 11:05:09 -0700 | Subject | PROBLEM: Off-by-one bug on sun4u SMP | From | Ryan Davis <> |
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On at least some sun4u machines, the CPU numbering starts at one not 0. This causes an off-by-one bug as other parts of the code assume zero-based numbering.
If you set max-cpus in the kernel config to the actual number of CPUs, the last CPU will be ignored and unused. This is because the CPU numbering starts at 1 but the code to check against max-cpus assumes a zero-based numbering.
On my computer: Sun Ultra 60 2x450mhz Ultrasparc. Building with max-cpus of 2 ignores the second cpu because 2 (one based cpu number) >= 2 (zero based max cpus) Rebuilding with a larger max-cpus is a workaround but non optimal. --- Those who will not reason, are bigots, those who cannot, are fools, and those who dare not, are slaves. -- Lord Byron -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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