Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | */ |
| 39 | struct 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 __MUTEX_INITIALIZER(name) \ |
| 53 | __SEMAPHORE_INITIALIZER(name,1) |
| 54 | |
| 55 | #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ |
| 56 | struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) |
| 57 | |
| 58 | #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) |
| 59 | #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) |
| 60 | |
| 61 | extern inline void sema_init (struct semaphore *sem, int val) |
| 62 | { |
| 63 | *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); |
| 64 | } |
| 65 | |
| 66 | static inline void init_MUTEX (struct semaphore *sem) |
| 67 | { |
| 68 | sema_init(sem, 1); |
| 69 | } |
| 70 | |
| 71 | static inline void init_MUTEX_LOCKED (struct semaphore *sem) |
| 72 | { |
| 73 | sema_init(sem, 0); |
| 74 | } |
| 75 | |
| 76 | static inline int sem_getcount(struct semaphore *sem) |
| 77 | { |
| 78 | return sem->count; |
| 79 | } |
| 80 | |
| 81 | asmlinkage void __down(struct semaphore * sem); |
| 82 | asmlinkage int __down_interruptible(struct semaphore * sem); |
| 83 | asmlinkage void __up(struct semaphore * sem); |
| 84 | |
| 85 | /* Semaphores can be `tried' from irq context. So we have to disable |
| 86 | * interrupts while we're messing with the semaphore. Sorry. |
| 87 | */ |
| 88 | |
| 89 | extern __inline__ void down(struct semaphore * sem) |
| 90 | { |
| 91 | might_sleep(); |
| 92 | spin_lock_irq(&sem->sentry); |
| 93 | if (sem->count > 0) { |
| 94 | sem->count--; |
| 95 | } else { |
| 96 | __down(sem); |
| 97 | } |
| 98 | spin_unlock_irq(&sem->sentry); |
| 99 | } |
| 100 | |
| 101 | extern __inline__ int down_interruptible(struct semaphore * sem) |
| 102 | { |
| 103 | int ret = 0; |
| 104 | might_sleep(); |
| 105 | spin_lock_irq(&sem->sentry); |
| 106 | if (sem->count > 0) { |
| 107 | sem->count--; |
| 108 | } else { |
| 109 | ret = __down_interruptible(sem); |
| 110 | } |
| 111 | spin_unlock_irq(&sem->sentry); |
| 112 | return ret; |
| 113 | } |
| 114 | |
| 115 | /* |
| 116 | * down_trylock returns 0 on success, 1 if we failed to get the lock. |
| 117 | * May not sleep, but must preserve irq state |
| 118 | */ |
| 119 | extern __inline__ int down_trylock(struct semaphore * sem) |
| 120 | { |
| 121 | int flags, count; |
| 122 | |
| 123 | spin_lock_irqsave(&sem->sentry, flags); |
| 124 | count = sem->count - 1; |
| 125 | if (count >= 0) |
| 126 | sem->count = count; |
| 127 | spin_unlock_irqrestore(&sem->sentry, flags); |
| 128 | return (count < 0); |
| 129 | } |
| 130 | |
| 131 | /* |
| 132 | * Note! This is subtle. We jump to wake people up only if |
| 133 | * the semaphore was negative (== somebody was waiting on it). |
| 134 | */ |
| 135 | extern __inline__ void up(struct semaphore * sem) |
| 136 | { |
| 137 | int flags; |
| 138 | spin_lock_irqsave(&sem->sentry, flags); |
| 139 | if (sem->count < 0) { |
| 140 | __up(sem); |
| 141 | } else { |
| 142 | sem->count++; |
| 143 | } |
| 144 | spin_unlock_irqrestore(&sem->sentry, flags); |
| 145 | } |
| 146 | |
| 147 | #endif /* _ASM_PARISC_SEMAPHORE_H */ |