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#ifndef _ALPHA_SEMAPHORE_H
#define _ALPHA_SEMAPHORE_H
/*
* SMP- and interrupt-safe semaphores..
*
* (C) Copyright 1996 Linus Torvalds
* (C) Copyright 1996, 2000 Richard Henderson
*/
#include <asm/current.h>
#include <asm/system.h>
#include <asm/atomic.h>
#include <linux/compiler.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#define DEBUG_SEMAPHORE 0
#define DEBUG_RW_SEMAPHORE 0
struct semaphore {
/* Careful, inline assembly knows about the position of these two. */
atomic_t count __attribute__((aligned(8)));
atomic_t waking; /* biased by -1 */
wait_queue_head_t wait;
#if WAITQUEUE_DEBUG
long __magic;
#endif
};
#if WAITQUEUE_DEBUG
# define __SEM_DEBUG_INIT(name) , (long)&(name).__magic
#else
# define __SEM_DEBUG_INIT(name)
#endif
#define __SEMAPHORE_INITIALIZER(name,count) \
{ ATOMIC_INIT(count), ATOMIC_INIT(-1), \
__WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
__SEM_DEBUG_INIT(name) }
#define __MUTEX_INITIALIZER(name) \
__SEMAPHORE_INITIALIZER(name,1)
#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)
{
/*
* Logically,
* *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
* except that gcc produces better initializing by parts yet.
*/
atomic_set(&sem->count, val);
atomic_set(&sem->waking, -1);
init_waitqueue_head(&sem->wait);
#if WAITQUEUE_DEBUG
sem->__magic = (long)&sem->__magic;
#endif
}
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);
}
extern void down(struct semaphore *);
extern void __down_failed(struct semaphore *);
extern int down_interruptible(struct semaphore *);
extern int __down_failed_interruptible(struct semaphore *);
extern int down_trylock(struct semaphore *);
extern void up(struct semaphore *);
extern void __up_wakeup(struct semaphore *);
/*
* Hidden out of line code is fun, but extremely messy. Rely on newer
* compilers to do a respectable job with this. The contention cases
* are handled out of line in arch/alpha/kernel/semaphore.c.
*/
static inline void __down(struct semaphore *sem)
{
long count = atomic_dec_return(&sem->count);
if (__builtin_expect(count < 0, 0))
__down_failed(sem);
}
static inline int __down_interruptible(struct semaphore *sem)
{
long count = atomic_dec_return(&sem->count);
if (__builtin_expect(count < 0, 0))
return __down_failed_interruptible(sem);
return 0;
}
/*
* down_trylock returns 0 on success, 1 if we failed to get the lock.
*
* We must manipulate count and waking simultaneously and atomically.
* Do this by using ll/sc on the pair of 32-bit words.
*/
static inline int __down_trylock(struct semaphore * sem)
{
long ret, tmp, tmp2, sub;
/* "Equivalent" C. Note that we have to do this all without
(taken) branches in order to be a valid ll/sc sequence.
do {
tmp = ldq_l;
sub = 0x0000000100000000;
ret = ((int)tmp <= 0); // count <= 0 ?
// Note that if count=0, the decrement overflows into
// waking, so cancel the 1 loaded above. Also cancel
// it if the lock was already free.
if ((int)tmp >= 0) sub = 0; // count >= 0 ?
ret &= ((long)tmp < 0); // waking < 0 ?
sub += 1;
if (ret) break;
tmp -= sub;
tmp = stq_c = tmp;
} while (tmp == 0);
*/
__asm__ __volatile__(
"1: ldq_l %1,%4\n"
" lda %3,1\n"
" addl %1,0,%2\n"
" sll %3,32,%3\n"
" cmple %2,0,%0\n"
" cmovge %2,0,%3\n"
" cmplt %1,0,%2\n"
" addq %3,1,%3\n"
" and %0,%2,%0\n"
" bne %0,2f\n"
" subq %1,%3,%1\n"
" stq_c %1,%4\n"
" beq %1,3f\n"
"2: mb\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub)
: "m"(*sem)
: "memory");
return ret;
}
static inline void __up(struct semaphore *sem)
{
long ret, tmp, tmp2, tmp3;
/* We must manipulate count and waking simultaneously and atomically.
Otherwise we have races between up and __down_failed_interruptible
waking up on a signal.
"Equivalent" C. Note that we have to do this all without
(taken) branches in order to be a valid ll/sc sequence.
do {
tmp = ldq_l;
ret = (int)tmp + 1; // count += 1;
tmp2 = tmp & 0xffffffff00000000; // extract waking
if (ret <= 0) // still sleepers?
tmp2 += 0x0000000100000000; // waking += 1;
tmp = ret & 0x00000000ffffffff; // insert count
tmp |= tmp2; // insert waking;
tmp = stq_c = tmp;
} while (tmp == 0);
*/
__asm__ __volatile__(
" mb\n"
"1: ldq_l %1,%4\n"
" addl %1,1,%0\n"
" zapnot %1,0xf0,%2\n"
" addq %2,%5,%3\n"
" cmovle %0,%3,%2\n"
" zapnot %0,0x0f,%1\n"
" bis %1,%2,%1\n"
" stq_c %1,%4\n"
" beq %1,3f\n"
"2:\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(tmp3)
: "m"(*sem), "r"(0x0000000100000000)
: "memory");
if (__builtin_expect(ret <= 0, 0))
__up_wakeup(sem);
}
#if !WAITQUEUE_DEBUG && !DEBUG_SEMAPHORE
extern inline void down(struct semaphore *sem)
{
__down(sem);
}
extern inline int down_interruptible(struct semaphore *sem)
{
return __down_interruptible(sem);
}
extern inline int down_trylock(struct semaphore *sem)
{
return __down_trylock(sem);
}
extern inline void up(struct semaphore *sem)
{
__up(sem);
}
#endif
#endif
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