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Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox <[email protected]> Acked-by: Ingo Molnar <[email protected]>
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Matthew Wilcox
Matthew Wilcox
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113 changed files with 314 additions and 7679 deletions
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#ifndef _ASM_PARISC_SEMAPHORE_HELPER_H
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#define _ASM_PARISC_SEMAPHORE_HELPER_H
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/*
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* SMP- and interrupt-safe semaphores helper functions.
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*
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* (C) Copyright 1996 Linus Torvalds
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* (C) Copyright 1999 Andrea Arcangeli
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*/
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/*
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* These two _must_ execute atomically wrt each other.
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*
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* This is trivially done with load_locked/store_cond,
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* which we have. Let the rest of the losers suck eggs.
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*/
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static __inline__ void wake_one_more(struct semaphore * sem)
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{
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atomic_inc((atomic_t *)&sem->waking);
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}
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static __inline__ int waking_non_zero(struct semaphore *sem)
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{
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unsigned long flags;
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int ret = 0;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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if (sem->waking > 0) {
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sem->waking--;
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ret = 1;
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}
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spin_unlock_irqrestore(&semaphore_wake_lock, flags);
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return ret;
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}
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/*
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* waking_non_zero_interruptible:
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* 1 got the lock
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* 0 go to sleep
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* -EINTR interrupted
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*
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* We must undo the sem->count down_interruptible() increment while we are
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* protected by the spinlock in order to make atomic this atomic_inc() with the
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* atomic_read() in wake_one_more(), otherwise we can race. -arca
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*/
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static __inline__ int waking_non_zero_interruptible(struct semaphore *sem,
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struct task_struct *tsk)
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{
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unsigned long flags;
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int ret = 0;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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if (sem->waking > 0) {
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sem->waking--;
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ret = 1;
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} else if (signal_pending(tsk)) {
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atomic_inc(&sem->count);
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ret = -EINTR;
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}
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spin_unlock_irqrestore(&semaphore_wake_lock, flags);
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return ret;
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}
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/*
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* waking_non_zero_trylock:
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* 1 failed to lock
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* 0 got the lock
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*
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* We must undo the sem->count down_trylock() increment while we are
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* protected by the spinlock in order to make atomic this atomic_inc() with the
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* atomic_read() in wake_one_more(), otherwise we can race. -arca
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*/
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static __inline__ int waking_non_zero_trylock(struct semaphore *sem)
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{
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unsigned long flags;
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int ret = 1;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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if (sem->waking <= 0)
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atomic_inc(&sem->count);
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else {
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sem->waking--;
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ret = 0;
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}
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spin_unlock_irqrestore(&semaphore_wake_lock, flags);
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return ret;
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}
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#endif /* _ASM_PARISC_SEMAPHORE_HELPER_H */
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@ -1,145 +1 @@
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/* SMP- and interrupt-safe semaphores.
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* PA-RISC version by Matthew Wilcox
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*
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* Linux/PA-RISC Project (http://www.parisc-linux.org/)
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* Copyright (C) 1996 Linus Torvalds
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* Copyright (C) 1999-2001 Matthew Wilcox < willy at debian d0T org >
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* Copyright (C) 2000 Grant Grundler < grundler a debian org >
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef _ASM_PARISC_SEMAPHORE_H
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#define _ASM_PARISC_SEMAPHORE_H
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#include <linux/spinlock.h>
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#include <linux/wait.h>
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#include <linux/rwsem.h>
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#include <asm/system.h>
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/*
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* The `count' is initialised to the number of people who are allowed to
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* take the lock. (Normally we want a mutex, so this is `1'). if
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* `count' is positive, the lock can be taken. if it's 0, no-one is
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* waiting on it. if it's -1, at least one task is waiting.
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*/
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struct semaphore {
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spinlock_t sentry;
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int count;
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wait_queue_head_t wait;
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};
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#define __SEMAPHORE_INITIALIZER(name, n) \
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{ \
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.sentry = SPIN_LOCK_UNLOCKED, \
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.count = n, \
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.wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
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}
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#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
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struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
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#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
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static inline void sema_init (struct semaphore *sem, int val)
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{
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*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
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}
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static inline void init_MUTEX (struct semaphore *sem)
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{
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sema_init(sem, 1);
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}
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static inline void init_MUTEX_LOCKED (struct semaphore *sem)
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{
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sema_init(sem, 0);
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}
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static inline int sem_getcount(struct semaphore *sem)
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{
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return sem->count;
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}
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asmlinkage void __down(struct semaphore * sem);
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asmlinkage int __down_interruptible(struct semaphore * sem);
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asmlinkage void __up(struct semaphore * sem);
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/* Semaphores can be `tried' from irq context. So we have to disable
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* interrupts while we're messing with the semaphore. Sorry.
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*/
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static inline void down(struct semaphore * sem)
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{
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might_sleep();
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spin_lock_irq(&sem->sentry);
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if (sem->count > 0) {
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sem->count--;
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} else {
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__down(sem);
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}
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spin_unlock_irq(&sem->sentry);
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}
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static inline int down_interruptible(struct semaphore * sem)
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{
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int ret = 0;
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might_sleep();
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spin_lock_irq(&sem->sentry);
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if (sem->count > 0) {
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sem->count--;
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} else {
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ret = __down_interruptible(sem);
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}
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spin_unlock_irq(&sem->sentry);
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return ret;
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}
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/*
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* down_trylock returns 0 on success, 1 if we failed to get the lock.
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* May not sleep, but must preserve irq state
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*/
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static inline int down_trylock(struct semaphore * sem)
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{
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unsigned long flags;
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int count;
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spin_lock_irqsave(&sem->sentry, flags);
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count = sem->count - 1;
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if (count >= 0)
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sem->count = count;
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spin_unlock_irqrestore(&sem->sentry, flags);
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return (count < 0);
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}
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/*
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* Note! This is subtle. We jump to wake people up only if
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* the semaphore was negative (== somebody was waiting on it).
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*/
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static inline void up(struct semaphore * sem)
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{
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unsigned long flags;
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spin_lock_irqsave(&sem->sentry, flags);
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if (sem->count < 0) {
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__up(sem);
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} else {
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sem->count++;
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}
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spin_unlock_irqrestore(&sem->sentry, flags);
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}
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#endif /* _ASM_PARISC_SEMAPHORE_H */
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#include <linux/semaphore.h>
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