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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]>
This commit is contained in:
Matthew Wilcox
Matthew Wilcox
parent
e48b3deee4
commit
64ac24e738
113 changed files with 314 additions and 7679 deletions
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/* Based on M68K version, Lineo Inc. May 2001 */
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#ifndef _BFIN_SEMAPHORE_HELPER_H
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#define _BFIN_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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*
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*/
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#include <asm/errno.h>
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/*
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* These two _must_ execute atomically wrt each other.
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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(&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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int ret;
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unsigned long flags = 0;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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ret = 0;
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if (atomic_read(&sem->waking) > 0) {
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atomic_dec(&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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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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int ret = 0;
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unsigned long flags = 0;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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if (atomic_read(&sem->waking) > 0) {
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atomic_dec(&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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static inline int waking_non_zero_trylock(struct semaphore *sem)
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{
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int ret = 1;
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unsigned long flags = 0;
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spin_lock_irqsave(&semaphore_wake_lock, flags);
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if (atomic_read(&sem->waking) > 0) {
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atomic_dec(&sem->waking);
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ret = 0;
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} else
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atomic_inc(&sem->count);
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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 /* _BFIN_SEMAPHORE_HELPER_H */
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@ -1,105 +1 @@
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#ifndef _BFIN_SEMAPHORE_H
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#define _BFIN_SEMAPHORE_H
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#ifndef __ASSEMBLY__
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#include <linux/linkage.h>
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#include <linux/wait.h>
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#include <linux/spinlock.h>
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#include <linux/rwsem.h>
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#include <asm/atomic.h>
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/*
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* Interrupt-safe semaphores..
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*
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* (C) Copyright 1996 Linus Torvalds
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*
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* BFIN version by akbar hussain Lineo Inc April 2001
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*
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*/
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struct semaphore {
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atomic_t count;
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int sleepers;
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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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.count = ATOMIC_INIT(n), \
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.sleepers = 0, \
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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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asmlinkage void __down(struct semaphore *sem);
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asmlinkage int __down_interruptible(struct semaphore *sem);
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asmlinkage int __down_trylock(struct semaphore *sem);
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asmlinkage void __up(struct semaphore *sem);
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extern spinlock_t semaphore_wake_lock;
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/*
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* This is ugly, but we want the default case to fall through.
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* "down_failed" is a special asm handler that calls the C
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* routine that actually waits.
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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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if (atomic_dec_return(&sem->count) < 0)
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__down(sem);
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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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if (atomic_dec_return(&sem->count) < 0)
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ret = __down_interruptible(sem);
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return (ret);
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}
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static inline int down_trylock(struct semaphore *sem)
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{
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int ret = 0;
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if (atomic_dec_return(&sem->count) < 0)
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ret = __down_trylock(sem);
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return ret;
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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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* The default case (no contention) will result in NO
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* jumps for both down() and up().
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*/
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static inline void up(struct semaphore *sem)
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{
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if (atomic_inc_return(&sem->count) <= 0)
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__up(sem);
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}
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#endif /* __ASSEMBLY__ */
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#endif /* _BFIN_SEMAPHORE_H */
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#include <linux/semaphore.h>
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