4b16bfbf8f
Chen, Kenneth W wrote: > The memory order semantics for include/asm-ia64/semaphore.h:down() > doesn't look right. It is using atomic_dec_return, which eventually > translate into ia64_fetch_and_add() that uses release semantics. > Shouldn't it use acquire semantics? Use ia64_fetchadd() instead of atomic_dec_return() Acked-by: Ken Chen <kenneth.w.chen@intel.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
100 lines
2.1 KiB
C
100 lines
2.1 KiB
C
#ifndef _ASM_IA64_SEMAPHORE_H
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#define _ASM_IA64_SEMAPHORE_H
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/*
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* Copyright (C) 1998-2000 Hewlett-Packard Co
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* Copyright (C) 1998-2000 David Mosberger-Tang <davidm@hpl.hp.com>
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*/
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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, 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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#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0)
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static inline void
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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
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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
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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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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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/*
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* Atomically decrement the semaphore's count. If it goes negative,
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* block the calling thread in the TASK_UNINTERRUPTIBLE state.
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*/
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static inline void
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down (struct semaphore *sem)
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{
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might_sleep();
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if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
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__down(sem);
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}
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/*
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* Atomically decrement the semaphore's count. If it goes negative,
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* block the calling thread in the TASK_INTERRUPTIBLE state.
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*/
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static inline int
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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 (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
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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
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down_trylock (struct semaphore *sem)
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{
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int ret = 0;
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if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
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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
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up (struct semaphore * sem)
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{
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if (ia64_fetchadd(1, &sem->count.counter, rel) <= -1)
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__up(sem);
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}
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#endif /* _ASM_IA64_SEMAPHORE_H */
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