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![Arun Sharma](/assets/img/avatar_default.png)
This allows us to move duplicated code in <asm/atomic.h> (atomic_inc_not_zero() for now) to <linux/atomic.h> Signed-off-by: Arun Sharma <asharma@fb.com> Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: David Miller <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Mike Frysinger <vapier@gentoo.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
34 lines
784 B
C
34 lines
784 B
C
#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/atomic.h>
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/*
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* This is an implementation of the notion of "decrement a
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* reference count, and return locked if it 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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int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
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{
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/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
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if (atomic_add_unless(atomic, -1, 1))
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return 0;
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/* Otherwise do it the slow way */
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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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