From 949cbb51197af9cfc56d70e976b4394ca460a81a Mon Sep 17 00:00:00 2001 From: Stefan Lankes Date: Tue, 26 Nov 2013 09:13:57 +0100 Subject: [PATCH] Add basic atomic operations which will be used in locking-mechanisms. --- arch/x86/include/asm/atomic.h | 167 ++++++++++++++++++++++++++++++++++ 1 file changed, 167 insertions(+) create mode 100644 arch/x86/include/asm/atomic.h diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h new file mode 100644 index 0000000..500687e --- /dev/null +++ b/arch/x86/include/asm/atomic.h @@ -0,0 +1,167 @@ +/* + * Copyright (c) 2010, Stefan Lankes, RWTH Aachen University + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * * Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this + * software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +/** + * @author Stefan Lankes + * @file arch/x86/include/asm/atomic.h + * @brief Functions for atomic operations + * + * This file defines functions for atomic operations on int32 variables + * which will be used in locking-mechanisms. + */ + +#ifndef __ARCH_ATOMIC_H__ +#define __ARCH_ATOMIC_H__ + +#include + +#ifdef __cplusplus +extern "C" { +#endif + +#if MAX_CORES > 1 +#define LOCK "lock ; " +#else +#define LOCK "" +#endif + +/** @brief Makro for initialization of atomic_int32_t vars + * + * Whenever you use an atomic_int32_t variable, init it with + * this macro first.\n + * Example: atomic_int32_t myAtomicVar = ATOMIC_INIT(123); + * + * @param i The number value you want to init it with. + */ +#define ATOMIC_INIT(i) { (i) } + +/** @brief Standard-datatype for atomic operations + * + * It just consists of an int32_t variable internally, marked as volatile. + */ +typedef struct { volatile int32_t counter; } atomic_int32_t; + +/** @brief Atomic test and set operation for int32 vars. + * + * This function will atomically exchange the value of an atomic variable and + * return its old value. Is used in locking-operations.\n + * \n + * Intel manuals: If a memory operand is referenced, the processor's locking + * protocol is automatically implemented for the duration of the exchange + * operation, regardless of the presence or absence of the LOCK prefix. + * + * @param d Pointer to the atomic_int_32_t with the value you want to exchange + * @param ret the value you want the var test for + * + * @return The old value of the atomic_int_32_t var before exchange + */ +inline static int32_t atomic_int32_test_and_set(atomic_int32_t* d, int32_t ret) +{ + asm volatile ("xchgl %0, %1" : "=r"(ret) : "m"(d->counter), "0"(ret) : "memory"); + return ret; +} + +/** @brief Atomic addition of values to atomic_int32_t vars + * + * This function lets you add values in an atomic operation + * + * @param d Pointer to the atomit_int32_t var you want do add a value to + * @param i The value you want to increment by + * + * @return The mathematical result + */ +inline static int32_t atomic_int32_add(atomic_int32_t *d, int32_t i) +{ + int32_t res = i; + asm volatile(LOCK "xaddl %0, %1" : "=r"(i) : "m"(d->counter), "0"(i) : "memory", "cc"); + return res+i; +} + +/** @brief Atomic subtraction of values from atomic_int32_t vars + * + * This function lets you subtract values in an atomic operation.\n + * This function is just for convenience. It uses atomic_int32_add(d, -i) + * + * @param d Pointer to the atomic_int32_t var you want to subtract from + * @param i The value you want to subtract by + * + * @return The mathematical result + */ +inline static int32_t atomic_int32_sub(atomic_int32_t *d, int32_t i) +{ + return atomic_int32_add(d, -i); +} + +/** @brief Atomic increment by one + * + * The atomic_int32_t var will be atomically incremented by one.\n + * + * @param d The atomic_int32_t var you want to increment + */ +inline static void atomic_int32_inc(atomic_int32_t* d) { + asm volatile(LOCK "incl %0" : "+m" (d->counter)); +} + +/** @brief Atomic decrement by one + * + * The atomic_int32_t var will be atomically decremented by one.\n + * + * @param d The atomic_int32_t var you want to decrement + */ +inline static void atomic_int32_dec(atomic_int32_t* d) { + asm volatile(LOCK "decl %0" : "+m" (d->counter)); +} + +/** @brief Read out an atomic_int32_t var + * + * This function is for convenience: It looks into the atomic_int32_t struct + * and returns the internal value for you. + * + * @param d Pointer to the atomic_int32_t var you want to read out + * @return It's number value + */ +inline static int32_t atomic_int32_read(atomic_int32_t *d) { + return d->counter; +} + +/** @brief Set the value of an atomic_int32_t var + * + * This function is for convenience: It sets the internal value of + * an atomic_int32_t var for you. + * + * @param d Pointer to the atomic_int32_t var you want to set + * @param v The value to set + */ +inline static void atomic_int32_set(atomic_int32_t *d, int32_t v) { + atomic_int32_test_and_set(d, v); +} + +#ifdef __cplusplus +} +#endif + +#endif