From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751352AbWACKIV (ORCPT ); Tue, 3 Jan 2006 05:08:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751141AbWACKHw (ORCPT ); Tue, 3 Jan 2006 05:07:52 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:62681 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1751332AbWACKHu (ORCPT ); Tue, 3 Jan 2006 05:07:50 -0500 Date: Tue, 3 Jan 2006 11:07:37 +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 04/19] mutex subsystem, add include/asm-i386/mutex.h Message-ID: <20060103100737.GD23289@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: -1.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.9 required=5.9 tests=ALL_TRUSTED,AWL autolearn=no SpamAssassin version=3.0.3 -2.8 ALL_TRUSTED Did not pass through any untrusted hosts 0.9 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 From: Arjan van de Ven add the i386 version of mutex.h, optimized in assembly. Signed-off-by: Arjan van de Ven Signed-off-by: Ingo Molnar ---- include/asm-i386/mutex.h | 136 +++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 136 insertions(+) Index: linux/include/asm-i386/mutex.h =================================================================== --- /dev/null +++ linux/include/asm-i386/mutex.h @@ -0,0 +1,136 @@ +/* + * Assembly implementation of the mutex fastpath, based on atomic + * decrement/increment. + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005 Red Hat, Inc., Ingo Molnar + */ +#ifndef _ASM_MUTEX_H +#define _ASM_MUTEX_H + +/** + * __mutex_fastpath_lock - try to take the lock by moving the count + * from 1 to a 0 value + * @count: pointer of type atomic_t + * @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 MUST leave the value lower than 1 + * even when the "1" assertion wasn't true. + */ +#define __mutex_fastpath_lock(count, fail_fn) \ +do { \ + unsigned int dummy; \ + \ + typecheck(atomic_t *, count); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ __volatile__( \ + LOCK " decl (%%eax) \n" \ + " js 2f \n" \ + "1: \n" \ + \ + LOCK_SECTION_START("") \ + "2: call "#fail_fn" \n" \ + " jmp 1b \n" \ + LOCK_SECTION_END \ + \ + :"=a" (dummy) \ + : "a" (count) \ + : "memory", "ecx", "edx"); \ +} 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 - try to promote the mutex from 0 to 1 + * @count: pointer of type atomic_t + * @fail_fn: function to call if the original value was not 0 + * + * try to promote the mutex from 0 to 1. if it wasn't 0, call . + * In the failure case, this function is allowed to either set the value + * to 1, or to set it to a value lower than 1. + * + * If the implementation sets it to a value of lower than 1, the + * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs + * to return 0 otherwise. + */ +#define __mutex_fastpath_unlock(count, fail_fn) \ +do { \ + unsigned int dummy; \ + \ + typecheck(atomic_t *, count); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ __volatile__( \ + LOCK " incl (%%eax) \n" \ + " jle 2f \n" \ + "1: \n" \ + \ + LOCK_SECTION_START("") \ + "2: call "#fail_fn" \n" \ + " jmp 1b \n" \ + LOCK_SECTION_END \ + \ + :"=a" (dummy) \ + : "a" (count) \ + : "memory", "ecx", "edx"); \ +} 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 a value lower than 1, and return 0 (failure) + * if it wasn't 1 originally, or return 1 (success) otherwise. This function + * MUST leave the value lower than 1 even when the "1" assertion wasn't true. + * Additionally, if the value was < 0 originally, this function must not leave + * it to 0 on failure. + */ +static inline int +__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) +{ + /* + * We have two variants here. The cmpxchg based one is the best one + * because it never induce a false contention state. It is included + * here because architectures using the inc/dec algorithms over the + * xchg ones are much more likely to support cmpxchg natively. + * + * If not we fall back to the spinlock based variant - that is + * just as efficient (and simpler) as a 'destructive' probing of + * the mutex state would be. + */ +#ifdef __HAVE_ARCH_CMPXCHG + if (likely(atomic_cmpxchg(count, 1, 0)) == 1) + return 1; + return 0; +#else + return fail_fn(count); +#endif +} + +#endif