1/* SMP- and interrupt-safe semaphores. 2 * PA-RISC version by Matthew Wilcox 3 * 4 * Linux/PA-RISC Project (http://www.parisc-linux.org/) 5 * Copyright (C) 1996 Linus Torvalds 6 * Copyright (C) 1999-2001 Matthew Wilcox < willy at debian d0T org > 7 * Copyright (C) 2000 Grant Grundler < grundler a debian org > 8 * 9 * This program is free software; you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License as published by 11 * the Free Software Foundation; either version 2 of the License, or 12 * (at your option) any later version. 13 * 14 * This program is distributed in the hope that it will be useful, 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 * GNU General Public License for more details. 18 * 19 * You should have received a copy of the GNU General Public License 20 * along with this program; if not, write to the Free Software 21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 22 */ 23 24#ifndef _ASM_PARISC_SEMAPHORE_H 25#define _ASM_PARISC_SEMAPHORE_H 26 27#include <linux/spinlock.h> 28#include <linux/wait.h> 29#include <linux/rwsem.h> 30 31#include <asm/system.h> 32 33/* 34 * The `count' is initialised to the number of people who are allowed to 35 * take the lock. (Normally we want a mutex, so this is `1'). if 36 * `count' is positive, the lock can be taken. if it's 0, no-one is 37 * waiting on it. if it's -1, at least one task is waiting. 38 */ 39struct semaphore { 40 spinlock_t sentry; 41 int count; 42 wait_queue_head_t wait; 43}; 44 45#define __SEMAPHORE_INITIALIZER(name, n) \ 46{ \ 47 .sentry = SPIN_LOCK_UNLOCKED, \ 48 .count = n, \ 49 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ 50} 51 52#define __DECLARE_SEMAPHORE_GENERIC(name,count) \ 53 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) 54 55#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) 56#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) 57 58extern inline void sema_init (struct semaphore *sem, int val) 59{ 60 *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); 61} 62 63static inline void init_MUTEX (struct semaphore *sem) 64{ 65 sema_init(sem, 1); 66} 67 68static inline void init_MUTEX_LOCKED (struct semaphore *sem) 69{ 70 sema_init(sem, 0); 71} 72 73static inline int sem_getcount(struct semaphore *sem) 74{ 75 return sem->count; 76} 77 78asmlinkage void __down(struct semaphore * sem); 79asmlinkage int __down_interruptible(struct semaphore * sem); 80asmlinkage void __up(struct semaphore * sem); 81 82/* Semaphores can be `tried' from irq context. So we have to disable 83 * interrupts while we're messing with the semaphore. Sorry. 84 */ 85 86extern __inline__ void down(struct semaphore * sem) 87{ 88 might_sleep(); 89 spin_lock_irq(&sem->sentry); 90 if (sem->count > 0) { 91 sem->count--; 92 } else { 93 __down(sem); 94 } 95 spin_unlock_irq(&sem->sentry); 96} 97 98extern __inline__ int down_interruptible(struct semaphore * sem) 99{ 100 int ret = 0; 101 might_sleep(); 102 spin_lock_irq(&sem->sentry); 103 if (sem->count > 0) { 104 sem->count--; 105 } else { 106 ret = __down_interruptible(sem); 107 } 108 spin_unlock_irq(&sem->sentry); 109 return ret; 110} 111 112/* 113 * down_trylock returns 0 on success, 1 if we failed to get the lock. 114 * May not sleep, but must preserve irq state 115 */ 116extern __inline__ int down_trylock(struct semaphore * sem) 117{ 118 unsigned long flags; 119 int count; 120 121 spin_lock_irqsave(&sem->sentry, flags); 122 count = sem->count - 1; 123 if (count >= 0) 124 sem->count = count; 125 spin_unlock_irqrestore(&sem->sentry, flags); 126 return (count < 0); 127} 128 129/* 130 * Note! This is subtle. We jump to wake people up only if 131 * the semaphore was negative (== somebody was waiting on it). 132 */ 133extern __inline__ void up(struct semaphore * sem) 134{ 135 unsigned long flags; 136 137 spin_lock_irqsave(&sem->sentry, flags); 138 if (sem->count < 0) { 139 __up(sem); 140 } else { 141 sem->count++; 142 } 143 spin_unlock_irqrestore(&sem->sentry, flags); 144} 145 146#endif /* _ASM_PARISC_SEMAPHORE_H */ 147