From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754077AbbERM1s (ORCPT ); Mon, 18 May 2015 08:27:48 -0400 Received: from www.osadl.org ([62.245.132.105]:33667 "EHLO www.osadl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753827AbbERM1i (ORCPT ); Mon, 18 May 2015 08:27:38 -0400 From: Nicholas Mc Guire To: Michal Marek Cc: Masahiro Yamada , Sam Ravnborg , Thomas Gleixner , "H. Peter Alvin" , Joe Perches , John Stultz , Andrew Hunter , Paul Turner , linux-kernel@vger.kernel.org, Nicholas Mc Guire Subject: [PATCH 2/3 V3] time: refactor msecs_to_jiffies Date: Mon, 18 May 2015 14:19:13 +0200 Message-Id: <1431951554-5563-2-git-send-email-hofrat@osadl.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1431951554-5563-1-git-send-email-hofrat@osadl.org> References: <1431951554-5563-1-git-send-email-hofrat@osadl.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Refactor the msecs_to_jiffies conditional code part in time.c and jiffies.h putting it into conditional functions rather than #ifdefs to improve readability. 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, and boot/run tested for x86 64 - x86_64_defconfig on an i3 Patch is against 4.1-rc3 (localversion-next is -next-20150518) Signed-off-by: Nicholas Mc Guire --- Thanks to Joe Perches for suggesting this approach and for his review comments on the first attempts and for his simple test-case that helped after I confused my self with .lst files. V3: refactoring of time.c/jiffies.h as requested by Thomas Gleixner without actually adding the builtin_constant_p() check include/linux/jiffies.h | 64 ++++++++++++++++++++++++++++++++++++++++++++++- kernel/time/time.c | 59 ++++++++++++++----------------------------- 2 files changed, 82 insertions(+), 41 deletions(-) diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index c367cbd..b41e026e 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -7,6 +7,7 @@ #include #include #include /* for HZ */ +#include /* * The following defines establish the engineering parameters of the PLL @@ -288,7 +289,68 @@ static inline u64 jiffies_to_nsecs(const unsigned long j) return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC; } -extern unsigned long msecs_to_jiffies(const unsigned int m); +extern unsigned long __msecs_to_jiffies(const unsigned int m); +#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) +/* + * HZ is equal to or smaller than 1000, and 1000 is a nice round + * multiple of HZ, divide with the factor between them, but round + * upwards: + */ +static inline unsigned long _msecs_to_jiffies(const unsigned int m) +{ + return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); +} +#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) +/* + * HZ is larger than 1000, and HZ is a nice round multiple of 1000 - + * simply multiply with the factor between them. + * + * But first make sure the multiplication result cannot overflow: + */ +static inline unsigned long _msecs_to_jiffies(const unsigned int m) +{ + if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) + return MAX_JIFFY_OFFSET; + return m * (HZ / MSEC_PER_SEC); +} +#else +/* + * Generic case - multiply, round and divide. But first check that if + * we are doing a net multiplication, that we wouldn't overflow: + */ +static inline unsigned long _msecs_to_jiffies(const unsigned int m) +{ + if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) + return MAX_JIFFY_OFFSET; + + return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) + >> MSEC_TO_HZ_SHR32; +} +#endif +/** + * msecs_to_jiffies: - convert milliseconds to jiffies + * @m: time in milliseconds + * + * conversion is done as follows: + * + * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) + * + * - 'too large' values [that would result in larger than + * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. + * + * - all other values are converted to jiffies by either multiplying + * the input value by a factor or dividing it with a factor and + * 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(). + */ +static inline unsigned long msecs_to_jiffies(const unsigned int m) +{ + return __msecs_to_jiffies(m); +} + extern unsigned long usecs_to_jiffies(const unsigned int u); extern unsigned long timespec_to_jiffies(const struct timespec *value); extern void jiffies_to_timespec(const unsigned long jiffies, diff --git a/kernel/time/time.c b/kernel/time/time.c index 4fa1d26..884bb8e 100644 --- a/kernel/time/time.c +++ b/kernel/time/time.c @@ -483,9 +483,11 @@ struct timespec64 ns_to_timespec64(const s64 nsec) } EXPORT_SYMBOL(ns_to_timespec64); #endif -/* - * When we convert to jiffies then we interpret incoming values - * the following way: +/** + * msecs_to_jiffies: - convert milliseconds to jiffies + * @m: time in milliseconds + * + * conversion is done as follows: * * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) * @@ -493,51 +495,28 @@ EXPORT_SYMBOL(ns_to_timespec64); * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. * * - all other values are converted to jiffies by either multiplying - * the input value by a factor or dividing it with a factor - * - * We must also be careful about 32-bit overflows. + * the input value by a factor or dividing it with a factor and + * handling any 32-bit overflows. + * for the details see __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 _msecs_to_jiffies helpers are the HZ dependent conversion + * routines found in include/linux/jiffies.h */ -unsigned long msecs_to_jiffies(const unsigned int m) +unsigned long __msecs_to_jiffies(const unsigned int m) { /* * Negative value, means infinite timeout: */ if ((int)m < 0) return MAX_JIFFY_OFFSET; - -#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) - /* - * HZ is equal to or smaller than 1000, and 1000 is a nice - * round multiple of HZ, divide with the factor between them, - * but round upwards: - */ - return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); -#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) - /* - * HZ is larger than 1000, and HZ is a nice round multiple of - * 1000 - simply multiply with the factor between them. - * - * But first make sure the multiplication result cannot - * overflow: - */ - if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) - return MAX_JIFFY_OFFSET; - - return m * (HZ / MSEC_PER_SEC); -#else - /* - * Generic case - multiply, round and divide. But first - * check that if we are doing a net multiplication, that - * we wouldn't overflow: - */ - if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) - return MAX_JIFFY_OFFSET; - - return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) - >> MSEC_TO_HZ_SHR32; -#endif + return _msecs_to_jiffies(m); } -EXPORT_SYMBOL(msecs_to_jiffies); +EXPORT_SYMBOL(__msecs_to_jiffies); unsigned long usecs_to_jiffies(const unsigned int u) { -- 1.7.10.4