On Wed, 23 Jul 2008 06:52:31 +0200 Willy Tarreau [off-list ref] wrote:
On Sun, Jul 13, 2008 at 02:55:25PM -0700, Andrew Morton wrote:
quoted
On Sun, 13 Jul 2008 23:51:06 +0200 Krzysztof Halasa [off-list ref] wrote:
quoted
Andrew Morton [off-list ref] writes:
quoted
--- a/include/asm-arm/bitops.h~a
+++ a/include/asm-arm/bitops.h
@@ -277,9 +277,16 @@ static inline int constant_fls(int x)
* the clz instruction for much better code efficiency.
*/
-#define fls(x) \
+#define __fls(x) \
( __builtin_constant_p(x) ? constant_fls(x) : \
({ int __r; asm("clz\t%0, %1" : "=r"(__r) : "r"(x) : "cc"); 32-__r; }) )
+
+/* Implement fls() in C so that 64-bit args are suitably truncated */
+static inline int fls(int x)
+{
+ return __fls(x);
+}
+
Well, I like it more as it fixes all possible places instead of only
fls64().
But... can't we just move the #define body into the inline fls(x)?
Will there be other users of __fls(x)? It seems the
__builtin_constant_p(x) works for inline functions.
Could. That was a minimal&safe thing.
quoted
The above patch fixes the kernel panic, too.
OK, thanks.
Andrew,
have you sent your patch to Linus ? I haven't seen it merged yet, and
I'd like to get it into -stable too.
This one?
From: Andrew Morton <akpm@linux-foundation.org>
arm's fls() is implemented as a macro, causing it to misbehave when passed
64-bit arguments. Fix.
Cc: Nickolay Vinogradov <redacted>
Tested-by: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
include/asm-arm/bitops.h | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff -puN include/asm-arm/bitops.h~arm-fix-fls-for-64-bit-arguments include/asm-arm/bitops.h
--- a/include/asm-arm/bitops.h~arm-fix-fls-for-64-bit-arguments
+++ a/include/asm-arm/bitops.h
@@ -277,9 +277,16 @@ static inline int constant_fls(int x)
* the clz instruction for much better code efficiency.
*/
-#define fls(x) \
+#define __fls(x) \
( __builtin_constant_p(x) ? constant_fls(x) : \
({ int __r; asm("clz\t%0, %1" : "=r"(__r) : "r"(x) : "cc"); 32-__r; }) )
+
+/* Implement fls() in C so that 64-bit args are suitably truncated */
+static inline int fls(int x)
+{
+ return __fls(x);
+}
+
#define ffs(x) ({ unsigned long __t = (x); fls(__t & -__t); })
#define __ffs(x) (ffs(x) - 1)
#define ffz(x) __ffs( ~(x) )_
Nope, I'm just kind of sitting on it. I'll put a stable@kernel.org tag
on it and send it to Russell I guess.