Messages in this thread Patch in this message | | | Date | Thu, 8 Apr 2004 12:47:52 -0700 | From | Paul Jackson <> | Subject | Patch 1/23 - Bitmaps, Cpumasks and Nodemasks |
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P1.bitmap_comment - Document bitmap.c bit model. Document the bitmap bit model, including handling of unused bits, and operation preconditions and postconditions.
Index: 2.6.5.bitmap/lib/bitmap.c =================================================================== --- 2.6.5.bitmap.orig/lib/bitmap.c 2004-04-05 02:00:15.000000000 -0700 +++ 2.6.5.bitmap/lib/bitmap.c 2004-04-05 02:50:25.000000000 -0700 @@ -12,6 +12,26 @@ #include <asm/bitops.h> #include <asm/uaccess.h> +/* + * bitmaps provide an array of bits, implemented using an an + * array of unsigned longs. The number of valid bits in a + * given bitmap need not be an exact multiple of BITS_PER_LONG. + * + * The possible unused bits in the last, partially used word + * of a bitmap are 'don't care'. The implementation makes + * no particular effort to keep them zero. It ensures that + * their value will not affect the results of any operation. + * The bitmap operations that return Boolean (bitmap_empty, + * for example) or scalar (bitmap_weight, for example) results + * carefully filter out these unused bits from impacting their + * results. + * + * Except for bitmap_complement, these operations hold to a + * slightly stronger rule: if you don't input any bitmaps to + * these ops that have some unused bits set, then they won't + * output any set unused bits in output bitmaps. + */ + #define MAX_BITMAP_BITS 512U /* for ia64 NR_CPUS maximum */ int bitmap_empty(const unsigned long *bitmap, int bits)
-- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson <pj@sgi.com> 1.650.933.1373 - 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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