* 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 <linux/compiler.h>
-#include <linux/config.h>
-#include <linux/spinlock.h>
+#include <asm/atomic.h>
+#include <asm/system.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
-#include <asm/atomic.h>
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
}
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 */
git://git.onelab.eu / linux-2.6.git / blobdiff