Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH] Fix order_base_2(0) | Date | Wed, 14 Dec 2011 11:40:17 +0000 |
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The order_base_2() function is either wrongly documented or wrongly implemented. In the preceding comment, it says that:
ob2(0) = 0
but this is not valid as roundup_pow_of_two()'s documentation asserts that:
* - the result is undefined when n == 0
Fix order_base_2(n) to actually return 0 when n == 0.
However, should we just instead define that the result of order_base_2(0) is undefined?
Signed-off-by: David Howells <dhowells@redhat.com> cc: Robert P. J. Day <rpjday@crashcourse.ca> cc: Andrew Morton <akpm@linux-foundation.org> ---
include/linux/log2.h | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/include/linux/log2.h b/include/linux/log2.h index fd7ff3d..d6463d8 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -202,7 +202,6 @@ unsigned long __rounddown_pow_of_two(unsigned long n) * ob2(5) = 3 * ... and so on. */ - -#define order_base_2(n) ilog2(roundup_pow_of_two(n)) +#define order_base_2(n) ((n) == 0 ? 0 : ilog2(roundup_pow_of_two(n))) #endif /* _LINUX_LOG2_H */
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