From: Andrei Warkentin <andreiw@vmware.com>
To: linux-kernel@vger.kernel.org
Cc: Andrei Warkentin <andreiw@vmware.com>
Subject: [PATCH] include/log2.h: Fix rounddown_pow_of_two(1)
Date: Tue, 8 Nov 2011 14:08:15 -0500 [thread overview]
Message-ID: <1320779295-17111-1-git-send-email-andreiw@vmware.com> (raw)
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.
Signed-off-by: Andrei Warkentin <andreiw@vmware.com>
---
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
next reply other threads:[~2011-11-08 19:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-08 19:08 Andrei Warkentin [this message]
2011-11-08 19:57 ` [PATCH] include/log2.h: Fix rounddown_pow_of_two(1) Jesper Juhl
2011-11-14 21:17 ` Andrei Warkentin
2011-11-14 23:27 ` Jesper Juhl
-- strict thread matches above, loose matches on Subject: below --
2011-11-16 19:56 Andrei Warkentin
2011-11-16 22:51 ` Rolf Eike Beer
2011-11-17 23:05 ` Andrew Morton
2011-11-18 18:46 ` Andrei Warkentin
2011-11-19 9:26 ` Marco Stornelli
2011-11-22 23:34 ` Guennadi Liakhovetski
2011-12-12 18:02 Dmitry Torokhov
2011-12-12 23:50 ` Linus Torvalds
2011-12-13 6:01 ` Dmitry Torokhov
2011-12-13 20:00 ` Peter Zijlstra
2011-12-13 20:05 ` Peter Zijlstra
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