43 lines
1.1 KiB
C
43 lines
1.1 KiB
C
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/*
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* Copyright (C) 2003 Jerome Marchand, Bull S.A.
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* Cleaned up by David Mosberger-Tang <davidm@hpl.hp.com>
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*
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* This file is released under the GPLv2, or at your option any later version.
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*
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* ia64 version of "atomic_dec_and_lock()" using the atomic "cmpxchg" instruction. This
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* code is an adaptation of the x86 version of "atomic_dec_and_lock()".
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*/
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#include <linux/compiler.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <asm/atomic.h>
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/*
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* Decrement REFCOUNT and if the count reaches zero, acquire the spinlock. Both of these
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* operations have to be done atomically, so that the count doesn't drop to zero without
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* acquiring the spinlock first.
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*/
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int
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_atomic_dec_and_lock (atomic_t *refcount, spinlock_t *lock)
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{
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int old, new;
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do {
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old = atomic_read(refcount);
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new = old - 1;
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if (unlikely (old == 1)) {
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/* oops, we may be decrementing to zero, do it the slow way... */
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spin_lock(lock);
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if (atomic_dec_and_test(refcount))
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return 1;
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spin_unlock(lock);
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return 0;
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}
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} while (cmpxchg(&refcount->counter, old, new) != old);
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return 0;
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}
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EXPORT_SYMBOL(_atomic_dec_and_lock);
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