From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932565AbWADOnJ (ORCPT ); Wed, 4 Jan 2006 09:43:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932553AbWADOmr (ORCPT ); Wed, 4 Jan 2006 09:42:47 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:38540 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S932567AbWADOmj (ORCPT ); Wed, 4 Jan 2006 09:42:39 -0500 Date: Wed, 4 Jan 2006 15:42:31 +0100 From: Ingo Molnar To: lkml Cc: Linus Torvalds , Andrew Morton , Arjan van de Ven , Nicolas Pitre , Jes Sorensen , Al Viro , Oleg Nesterov , David Howells , Alan Cox , Christoph Hellwig , Andi Kleen , Russell King Subject: [patch 05/21] mutex subsystem, add include/asm-x86_64/mutex.h Message-ID: <20060104144231.GF27646@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=no SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org add the x86_64 version of mutex.h, optimized in assembly. Signed-off-by: Ingo Molnar Signed-off-by: Arjan van de Ven ---- include/asm-x86_64/mutex.h | 113 +++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 113 insertions(+) Index: linux/include/asm-x86_64/mutex.h =================================================================== --- /dev/null +++ linux/include/asm-x86_64/mutex.h @@ -0,0 +1,113 @@ +/* + * Assembly implementation of the mutex fastpath, based on atomic + * decrement/increment. + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar + */ +#ifndef _ASM_MUTEX_H +#define _ASM_MUTEX_H + +/** + * __mutex_fastpath_lock - decrement and call function if negative + * @v: pointer of type atomic_t + * @fail_fn: function to call if the result is negative + * + * Atomically decrements @v and calls if the result is negative. + */ +#define __mutex_fastpath_lock(v, fail_fn) \ +do { \ + unsigned long dummy; \ + \ + typecheck(atomic_t *, v); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ __volatile__( \ + LOCK " decl (%%rdi) \n" \ + " js 2f \n" \ + "1: \n" \ + \ + LOCK_SECTION_START("") \ + "2: call "#fail_fn" \n" \ + " jmp 1b \n" \ + LOCK_SECTION_END \ + \ + :"=D" (dummy) \ + : "D" (v) \ + : "rax", "rsi", "rdx", "rcx", \ + "r8", "r9", "r10", "r11", "memory"); \ +} while (0) + +/** + * __mutex_fastpath_lock_retval - try to take the lock by moving the count + * from 1 to a 0 value + * @count: pointer of type atomic_t + * @fail_fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call if + * it wasn't 1 originally. This function returns 0 if the fastpath succeeds, + * or anything the slow path function returns + */ +static inline int +__mutex_fastpath_lock_retval(atomic_t *count, + int fastcall (*fail_fn)(atomic_t *)) +{ + if (unlikely(atomic_dec_return(count) < 0)) + return fail_fn(count); + else + return 0; +} + +/** + * __mutex_fastpath_unlock - increment and call function if nonpositive + * @v: pointer of type atomic_t + * @fail_fn: function to call if the result is nonpositive + * + * Atomically increments @v and calls if the result is nonpositive. + */ +#define __mutex_fastpath_unlock(v, fail_fn) \ +do { \ + unsigned long dummy; \ + \ + typecheck(atomic_t *, v); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ __volatile__( \ + LOCK " incl (%%rdi) \n" \ + " jle 2f \n" \ + "1: \n" \ + \ + LOCK_SECTION_START("") \ + "2: call "#fail_fn" \n" \ + " jmp 1b \n" \ + LOCK_SECTION_END \ + \ + :"=D" (dummy) \ + : "D" (v) \ + : "rax", "rsi", "rdx", "rcx", \ + "r8", "r9", "r10", "r11", "memory"); \ +} while (0) + +#define __mutex_slowpath_needs_to_unlock() 1 + +/** + * __mutex_fastpath_trylock - try to acquire the mutex, without waiting + * + * @count: pointer of type atomic_t + * @fail_fn: fallback function + * + * Change the count from 1 to 0 and return 1 (success), or return 0 (failure) + * if it wasn't 1 originally. [the fallback function is never used on + * x86_64, because all x86_64 CPUs have a CMPXCHG instruction.] + */ +static inline int +__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) +{ + if (likely(atomic_cmpxchg(count, 1, 0)) == 1) + return 1; + else + return 0; +} + +#endif