On 11/13/2017 07:22 PM, Robert Elliott wrote:
> Fix cpumask manipulation on (64-bit) Windows systems.
>
> cpus_allowed=nn values greater than 32 does not work, due to
> * the compiler not promoting expressions like "1 << cpu" to
> 64 bits
> * the clear function clearing the wrong bit (using "cpu - 1"),
> * the clear function using XOR to clear (which only works if the
> bit was previously set)
> * the check function returning a 64-bit value through a 32-bit
> return value
>
> Example problems (from extra debug prints):
> * setting CPU 32 really sets bit 0 (CPU 0)
> Set mask of 0000000000000000 to add 0000000000000001 (32)
>
> * setting CPU 63 really sets bit 31 (CPU 31)
> Set mask of 0000000000000000 to add 0000000080000000 (63)
>
> * clearing CPU 0 really clears bit 63 (CPU 63)
> Clear mask of 0000000055555555 to remove 8000000000000000 (0)
>
> * clearing CPU 2 really clears bit 2 (CPU 2)
> Clear mask of 0000000055555555 to remove 0000000000000002 (2)
>
> * checking claims CPU 32 is not in a mask of CPUs {32,34,36,38}
> for 0000005500000000 check if bit 32 is set ==> FALSE
Classic error... Thanks Robert, applied.
--
Jens Axboe
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