To allow constant folding in msecs_to_jiffies() conditionally calls the HZ dependent _msecs_to_jiffies() helpers or, when gcc can not figure out constant folding, __msecs_to_jiffies which is the renamed original msecs_to_jiffies() function.
Patch was build tested for: arm - imx_v6_v7_defconfig, vexpress_defconfig cris - etrax-100lx_v2_defconfig m68k - multi_defconfig mips32 - ar7_defconfig, mips64 - loongson3_defconfig powerpc - 44x/virtex5_defconfig powerpc64 - powerpc64_defconfig sh - se7780_defconfig, sparc32 - sparc32_defconfig sparc64 - sparc64_defconfig x86 64 - x86_64_defconfig, boot and run testing: x86 64 - x86_64_defconfig i3 Patch is against 4.1-rc3 (localversion-next is -next-20150518) Signed-off-by: Nicholas Mc Guire <[email protected]> --- Thanks to Joe Perches <[email protected]> for suggesting this approach and for his review comments on the first attempts. include/linux/jiffies.h | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index b41e026e..e96996a 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -343,12 +343,24 @@ static inline unsigned long _msecs_to_jiffies(const unsigned int m) * handling any 32-bit overflows. * for the details see __msecs_to_jiffies() * - * the HZ range specific helpers _msecs_to_jiffies() are called from - * __msecs_to_jiffies(). + * msecs_to_jiffies() checks for the passed in value being a constant + * via __builtin_constant_p() allowing gcc to eliminate most of the + * code, __msecs_to_jiffies() is called if the value passed does not + * allow constant folding and the actual conversion must be done at + * runtime. + * the HZ range specific helpers _msecs_to_jiffies() are called both + * directly here and from __msecs_to_jiffies() in the case where + * constant folding is not possible. */ static inline unsigned long msecs_to_jiffies(const unsigned int m) { - return __msecs_to_jiffies(m); + if (__builtin_constant_p(m)) { + if ((int)m < 0) + return MAX_JIFFY_OFFSET; + return _msecs_to_jiffies(m); + } else { + return __msecs_to_jiffies(m); + } } extern unsigned long usecs_to_jiffies(const unsigned int u); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
