1 is a power of two, therefore rounddown_pow_of_two(1) should return 1. It does
in case the argument is a variable but in case it's a constant it behaves
wrong and returns 0. Probably nobody ever did it so this was never noticed,
however net/drivers/vmxnet3 with latest GCC does and breaks on unicpu systems.
This is similar to Rolf's patch to roundup_pow_of_two(1).
Cc: Rolf Eike Beer
Cc: opensuse-kernel@opensuse.org
Reviewed-by: Jesper Juhl
Signed-off-by: Andrei Warkentin
---
include/linux/log2.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/linux/log2.h b/include/linux/log2.h
index 25b8086..ccda848 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -185,7 +185,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
#define rounddown_pow_of_two(n) \
( \
__builtin_constant_p(n) ? ( \
- (n == 1) ? 0 : \
+ (n == 1) ? 1 : \
(1UL << ilog2(n))) : \
__rounddown_pow_of_two(n) \
)
--
1.7.4.1
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