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[PATCH] atomic: inc_not_zero
Introduce an atomic_inc_not_zero operation. Make this a special case of atomic_add_unless because lockless pagecache actually wants atomic_inc_not_negativeone due to its offset refcount. Signed-off-by: Nick Piggin <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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23 changed files with 321 additions and 1 deletions
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@ -200,6 +200,16 @@ atomic_compare_and_swap(int expected_oldval,int new_val,atomic_t *v)
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#define atomic_cmpxchg(v, o, n) (atomic_compare_and_swap((o), (n), &((v)->counter)))
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#define atomic_add_unless(v, a, u) \
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({ \
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int c, old; \
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c = atomic_read(v); \
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while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
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c = old; \
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c != (u); \
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})
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#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
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#define smp_mb__before_atomic_dec() smp_mb()
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#define smp_mb__after_atomic_dec() smp_mb()
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#define smp_mb__before_atomic_inc() smp_mb()
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