/* * SMP- and interrupt-safe semaphores. * * Copyright (C) 2006 Atmel Corporation * * Based on include/asm-i386/semaphore.h * Copyright (C) 1996 Linus Torvalds * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #ifndef __ASM_AVR32_SEMAPHORE_H #define __ASM_AVR32_SEMAPHORE_H #include <linux/linkage.h> #include <asm/system.h> #include <asm/atomic.h> #include <linux/wait.h> #include <linux/rwsem.h> struct semaphore { atomic_t count; int sleepers; wait_queue_head_t wait; }; #define __SEMAPHORE_INITIALIZER(name, n) \ { \ .count = ATOMIC_INIT(n), \ .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ } #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) static inline void sema_init (struct semaphore *sem, int val) { atomic_set(&sem->count, val); sem->sleepers = 0; init_waitqueue_head(&sem->wait); } static inline void init_MUTEX (struct semaphore *sem) { sema_init(sem, 1); } static inline void init_MUTEX_LOCKED (struct semaphore *sem) { sema_init(sem, 0); } void __down(struct semaphore * sem); int __down_interruptible(struct semaphore * sem); void __up(struct semaphore * sem); /* * This is ugly, but we want the default case to fall through. * "__down_failed" is a special asm handler that calls the C * routine that actually waits. See arch/i386/kernel/semaphore.c */ static inline void down(struct semaphore * sem) { might_sleep(); if (unlikely(atomic_dec_return (&sem->count) < 0)) __down (sem); } /* * Interruptible try to acquire a semaphore. If we obtained * it, return zero. If we were interrupted, returns -EINTR */ static inline int down_interruptible(struct semaphore * sem) { int ret = 0; might_sleep(); if (unlikely(atomic_dec_return (&sem->count) < 0)) ret = __down_interruptible (sem); return ret; } /* * Non-blockingly attempt to down() a semaphore. * Returns zero if we acquired it */ static inline int down_trylock(struct semaphore * sem) { return atomic_dec_if_positive(&sem->count) < 0; } /* * Note! This is subtle. We jump to wake people up only if * the semaphore was negative (== somebody was waiting on it). * The default case (no contention) will result in NO * jumps for both down() and up(). */ static inline void up(struct semaphore * sem) { if (unlikely(atomic_inc_return (&sem->count) <= 0)) __up (sem); } #endif /*__ASM_AVR32_SEMAPHORE_H */