From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754743AbbFLJcQ (ORCPT ); Fri, 12 Jun 2015 05:32:16 -0400 Received: from terminus.zytor.com ([198.137.202.10]:34452 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752305AbbFLJbd (ORCPT ); Fri, 12 Jun 2015 05:31:33 -0400 Date: Fri, 12 Jun 2015 02:30:56 -0700 From: tip-bot for Nicholas Mc Guire Message-ID: Cc: yamada.m@jp.panasonic.com, joe@perches.com, hpa@zytor.com, mingo@kernel.org, ahh@google.com, tglx@linutronix.de, john.stultz@linaro.org, mmarek@suse.cz, pjt@google.com, linux-kernel@vger.kernel.org, hofrat@osadl.org, sam@ravnborg.org Reply-To: sam@ravnborg.org, hofrat@osadl.org, linux-kernel@vger.kernel.org, pjt@google.com, mmarek@suse.cz, tglx@linutronix.de, john.stultz@linaro.org, ahh@google.com, mingo@kernel.org, hpa@zytor.com, joe@perches.com, yamada.m@jp.panasonic.com In-Reply-To: <1432832996-12129-2-git-send-email-hofrat@osadl.org> References: <1432832996-12129-2-git-send-email-hofrat@osadl.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/core] time: Allow gcc to fold usecs_to_jiffies( constant) Git-Commit-ID: c569a23d65ac2900d9998d3fe04044fe95be6b2f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: c569a23d65ac2900d9998d3fe04044fe95be6b2f Gitweb: http://git.kernel.org/tip/c569a23d65ac2900d9998d3fe04044fe95be6b2f Author: Nicholas Mc Guire AuthorDate: Thu, 28 May 2015 19:09:56 +0200 Committer: Thomas Gleixner CommitDate: Wed, 10 Jun 2015 11:31:14 +0200 time: Allow gcc to fold usecs_to_jiffies(constant) To allow constant folding in usecs_to_jiffies() conditionally calls the HZ dependent _usecs_to_jiffies() helpers or, when gcc can not figure out constant folding, __usecs_to_jiffies, which is the renamed original usecs_to_jiffies() function. Signed-off-by: Nicholas Mc Guire Cc: Masahiro Yamada Cc: Sam Ravnborg Cc: Joe Perches Cc: John Stultz Cc: Andrew Hunter Cc: Paul Turner Cc: Michal Marek Link: http://lkml.kernel.org/r/1432832996-12129-2-git-send-email-hofrat@osadl.org Signed-off-by: Thomas Gleixner --- include/linux/jiffies.h | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index a316ebe..535fd3b 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -383,9 +383,37 @@ static inline unsigned long _usecs_to_jiffies(const unsigned int u) } #endif +/** + * usecs_to_jiffies: - convert microseconds to jiffies + * @u: time in microseconds + * + * conversion is done as follows: + * + * - '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 as for msecs_to_jiffies. + * + * usecs_to_jiffies() checks for the passed in value being a constant + * via __builtin_constant_p() allowing gcc to eliminate most of the + * code, __usecs_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 _usecs_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 usecs_to_jiffies(const unsigned int u) { - return __usecs_to_jiffies(u); + if (__builtin_constant_p(u)) { + if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) + return MAX_JIFFY_OFFSET; + return _usecs_to_jiffies(u); + } else { + return __usecs_to_jiffies(u); + } } extern unsigned long timespec_to_jiffies(const struct timespec *value);