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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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113 changed files with 314 additions and 7679 deletions
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#ifndef __V850_SEMAPHORE_H__
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#define __V850_SEMAPHORE_H__
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#include <linux/linkage.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/atomic.h>
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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,count) \
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{ ATOMIC_INIT (count), 0, \
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__WAIT_QUEUE_HEAD_INITIALIZER ((name).wait) }
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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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/*
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* special register calling convention
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*/
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asmlinkage void __down_failed (void);
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asmlinkage int __down_interruptible_failed (void);
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asmlinkage int __down_trylock_failed (void);
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asmlinkage void __up_wakeup (void);
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extern void __down (struct semaphore * sem);
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extern int __down_interruptible (struct semaphore * sem);
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extern int __down_trylock (struct semaphore * sem);
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extern void __up (struct semaphore * sem);
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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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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 /* __V850_SEMAPHORE_H__ */
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#include <linux/semaphore.h>
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