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40 lines
779 B
40 lines
779 B
/*
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* x86 version of "atomic_dec_and_lock()" using
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* the atomic "cmpxchg" instruction.
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*
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* (For CPU's lacking cmpxchg, we use the slow
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* generic version, and this one never even gets
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* compiled).
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*/
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#include <linux/spinlock.h>
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#include <asm/atomic.h>
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int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
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{
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int counter;
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int newcount;
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repeat:
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counter = atomic_read(atomic);
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newcount = counter-1;
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if (!newcount)
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goto slow_path;
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asm volatile("lock; cmpxchgl %1,%2"
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:"=a" (newcount)
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:"r" (newcount), "m" (atomic->counter), "0" (counter));
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/* If the above failed, "eax" will have changed */
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if (newcount != counter)
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goto repeat;
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return 0;
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slow_path:
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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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