X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;ds=sidebyside;f=include%2Fasm-mips%2Fsemaphore.h;h=ed9a3d774c6af72acdb002547988ed40ba8c2862;hb=9bf4aaab3e101692164d49b7ca357651eb691cb6;hp=bab913a9064433ddb654bc882f924fb6ce76bff3;hpb=db216c3d5e4c040e557a50f8f5d35d5c415e8c1c;p=linux-2.6.git diff --git a/include/asm-mips/semaphore.h b/include/asm-mips/semaphore.h index bab913a90..ed9a3d774 100644 --- a/include/asm-mips/semaphore.h +++ b/include/asm-mips/semaphore.h @@ -4,61 +4,70 @@ * for more details. * * Copyright (C) 1996 Linus Torvalds - * Copyright (C) 1998, 99, 2000, 01 Ralf Baechle + * Copyright (C) 1998, 99, 2000, 01, 04 Ralf Baechle * Copyright (C) 1999, 2000, 01 Silicon Graphics, Inc. * Copyright (C) 2000, 01 MIPS Technologies, Inc. + * + * In all honesty, little of the old MIPS code left - the PPC64 variant was + * just looking nice and portable so I ripped it. Credits to whoever wrote + * it. */ -#ifndef _ASM_SEMAPHORE_H -#define _ASM_SEMAPHORE_H +#ifndef __ASM_SEMAPHORE_H +#define __ASM_SEMAPHORE_H + +/* + * Remove spinlock-based RW semaphores; RW semaphore definitions are + * now in rwsem.h and we use the generic lib/rwsem.c implementation. + * Rework semaphores to use atomic_dec_if_positive. + * -- Paul Mackerras (paulus@samba.org) + */ + +#ifdef __KERNEL__ -#include -#include -#include +#include +#include #include #include -#include struct semaphore { -#ifdef __MIPSEB__ - atomic_t count; - atomic_t waking; -#else - atomic_t waking; + /* + * Note that any negative value of count is equivalent to 0, + * but additionally indicates that some process(es) might be + * sleeping on `wait'. + */ atomic_t count; -#endif wait_queue_head_t wait; -#if WAITQUEUE_DEBUG +#ifdef WAITQUEUE_DEBUG long __magic; #endif -} __attribute__((aligned(8))); +}; -#if WAITQUEUE_DEBUG -# define __SEM_DEBUG_INIT(name) , .__magic = (long)&(name).__magic +#ifdef WAITQUEUE_DEBUG +# define __SEM_DEBUG_INIT(name) \ + , (long)&(name).__magic #else # define __SEM_DEBUG_INIT(name) #endif -#define __SEMAPHORE_INITIALIZER(name,_count) { \ - .count = ATOMIC_INIT(_count), \ - .waking = ATOMIC_INIT(0), \ - .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ - __SEM_DEBUG_INIT(name) \ -} +#define __SEMAPHORE_INITIALIZER(name, count) \ + { ATOMIC_INIT(count), \ + __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ + __SEM_DEBUG_INIT(name) } -#define __MUTEX_INITIALIZER(name) __SEMAPHORE_INITIALIZER(name, 1) +#define __MUTEX_INITIALIZER(name) \ + __SEMAPHORE_INITIALIZER(name, 1) -#define __DECLARE_SEMAPHORE_GENERIC(name,count) \ - struct semaphore name = __SEMAPHORE_INITIALIZER(name, count) +#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) +#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); - atomic_set(&sem->waking, 0); init_waitqueue_head(&sem->wait); -#if WAITQUEUE_DEBUG +#ifdef WAITQUEUE_DEBUG sem->__magic = (long)&sem->__magic; #endif } @@ -73,211 +82,57 @@ static inline void init_MUTEX_LOCKED (struct semaphore *sem) sema_init(sem, 0); } -#ifndef CONFIG_CPU_HAS_LLDSCD -/* - * On machines without lld/scd we need a spinlock to make the manipulation of - * sem->count and sem->waking atomic. - */ -extern spinlock_t semaphore_lock; -#endif - -extern void __down_failed(struct semaphore * sem); -extern int __down_failed_interruptible(struct semaphore * sem); -extern void __up_wakeup(struct semaphore * sem); +extern void __down(struct semaphore * sem); +extern int __down_interruptible(struct semaphore * sem); +extern void __up(struct semaphore * sem); static inline void down(struct semaphore * sem) { - int count; - -#if WAITQUEUE_DEBUG +#ifdef WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif might_sleep(); - count = atomic_dec_return(&sem->count); - if (unlikely(count < 0)) - __down_failed(sem); + + /* + * Try to get the semaphore, take the slow path if we fail. + */ + 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 count; + int ret = 0; -#if WAITQUEUE_DEBUG +#ifdef WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif might_sleep(); - count = atomic_dec_return(&sem->count); - if (unlikely(count < 0)) - return __down_failed_interruptible(sem); - - return 0; -} - -#ifdef CONFIG_CPU_HAS_LLDSCD - -/* - * down_trylock returns 0 on success, 1 if we failed to get the lock. - * - * We must manipulate count and waking simultaneously and atomically. - * Here, we do this by using lld/scd on the pair of 32-bit words. - * - * Pseudocode: - * - * Decrement(sem->count) - * If(sem->count >=0) { - * Return(SUCCESS) // resource is free - * } else { - * If(sem->waking <= 0) { // if no wakeup pending - * Increment(sem->count) // undo decrement - * Return(FAILURE) - * } else { - * Decrement(sem->waking) // otherwise "steal" wakeup - * Return(SUCCESS) - * } - * } - */ -static inline int down_trylock(struct semaphore * sem) -{ - long ret, tmp, tmp2, sub; - -#if WAITQUEUE_DEBUG - CHECK_MAGIC(sem->__magic); -#endif - - __asm__ __volatile__( - " .set mips3 # down_trylock \n" - "0: lld %1, %4 \n" - " dli %3, 0x0000000100000000 # count -= 1 \n" - " dsubu %1, %3 \n" - " li %0, 0 # ret = 0 \n" - " bgez %1, 2f # if count >= 0 \n" - " sll %2, %1, 0 # extract waking \n" - " blez %2, 1f # if waking < 0 -> 1f \n" - " daddiu %1, %1, -1 # waking -= 1 \n" - " b 2f \n" - "1: daddu %1, %1, %3 # count += 1 \n" - " li %0, 1 # ret = 1 \n" - "2: scd %1, %4 \n" - " beqz %1, 0b \n" - " sync \n" - " .set mips0 \n" - : "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub) - : "m"(*sem) - : "memory"); + if (unlikely(atomic_dec_return(&sem->count) < 0)) + ret = __down_interruptible(sem); return ret; } -/* - * Note! This is subtle. We jump to wake people up only if - * the semaphore was negative (== somebody was waiting on it). - */ -static inline void up(struct semaphore * sem) -{ - unsigned long tmp, tmp2; - int count; - -#if WAITQUEUE_DEBUG - CHECK_MAGIC(sem->__magic); -#endif - /* - * We must manipulate count and waking simultaneously and atomically. - * Otherwise we have races between up and __down_failed_interruptible - * waking up on a signal. - */ - - __asm__ __volatile__( - " .set mips3 \n" - " sync # up \n" - "1: lld %1, %3 \n" - " dsra32 %0, %1, 0 # extract count to %0 \n" - " daddiu %0, 1 # count += 1 \n" - " slti %2, %0, 1 # %3 = (%0 <= 0) \n" - " daddu %1, %2 # waking += %3 \n" - " dsll32 %1, %1, 0 # zero-extend %1 \n" - " dsrl32 %1, %1, 0 \n" - " dsll32 %2, %0, 0 # Reassemble union \n" - " or %1, %2 # from count and waking \n" - " scd %1, %3 \n" - " beqz %1, 1b \n" - " .set mips0 \n" - : "=&r"(count), "=&r"(tmp), "=&r"(tmp2), "+m"(*sem) - : - : "memory"); - - if (unlikely(count <= 0)) - __up_wakeup(sem); -} - -#else - -/* - * Non-blockingly attempt to down() a semaphore. - * Returns zero if we acquired it - */ static inline int down_trylock(struct semaphore * sem) { - unsigned long flags; - int count, waking; - int ret = 0; - -#if WAITQUEUE_DEBUG +#ifdef WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif - spin_lock_irqsave(&semaphore_lock, flags); - count = atomic_read(&sem->count) - 1; - atomic_set(&sem->count, count); - if (unlikely(count < 0)) { - waking = atomic_read(&sem->waking); - if (waking <= 0) { - atomic_set(&sem->count, count + 1); - ret = 1; - } else { - atomic_set(&sem->waking, waking - 1); - ret = 0; - } - } - spin_unlock_irqrestore(&semaphore_lock, flags); - - return ret; + 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). - */ static inline void up(struct semaphore * sem) { - unsigned long flags; - int count, waking; - -#if WAITQUEUE_DEBUG +#ifdef WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif - /* - * We must manipulate count and waking simultaneously and atomically. - * Otherwise we have races between up and __down_failed_interruptible - * waking up on a signal. - */ - - spin_lock_irqsave(&semaphore_lock, flags); - count = atomic_read(&sem->count) + 1; - waking = atomic_read(&sem->waking); - if (count <= 0) - waking++; - atomic_set(&sem->count, count); - atomic_set(&sem->waking, waking); - spin_unlock_irqrestore(&semaphore_lock, flags); - if (unlikely(count <= 0)) - __up_wakeup(sem); + if (unlikely(atomic_inc_return(&sem->count) <= 0)) + __up(sem); } -#endif /* CONFIG_CPU_HAS_LLDSCD */ +#endif /* __KERNEL__ */ -#endif /* _ASM_SEMAPHORE_H */ +#endif /* __ASM_SEMAPHORE_H */