38 lines
927 B
C
38 lines
927 B
C
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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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* This is an architecture-neutral, but slow,
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* implementation of the notion of "decrement
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* a reference count, and return locked if it
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* decremented to zero".
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*
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* NOTE NOTE NOTE! This is _not_ equivalent to
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*
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* if (atomic_dec_and_test(&atomic)) {
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* spin_lock(&lock);
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* return 1;
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* }
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* return 0;
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*
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* because the spin-lock and the decrement must be
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* "atomic".
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*
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* This slow version gets the spinlock unconditionally,
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* and releases it if it isn't needed. Architectures
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* are encouraged to come up with better approaches,
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* this is trivially done efficiently using a load-locked
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* store-conditional approach, for example.
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*/
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int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
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{
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spin_lock(lock);
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if (atomic_dec_and_test(atomic))
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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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EXPORT_SYMBOL(_atomic_dec_and_lock);
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