atomic.h

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/* Atomic operations usable in machine independent code */
#ifndef _LINUX_ATOMIC_H
#define _LINUX_ATOMIC_H
#include <asm/atomic.h>

static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
    return __atomic_add_unless(v, a, u) != u;
}

#ifndef atomic_inc_not_zero
#define atomic_inc_not_zero(v)      atomic_add_unless((v), 1, 0)
#endif

#ifndef atomic_inc_not_zero_hint
static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
{
    int val, c = hint;

    /* sanity test, should be removed by compiler if hint is a constant */
    if (!hint)
        return atomic_inc_not_zero(v);

    do {
        val = atomic_cmpxchg(v, c, c + 1);
        if (val == c)
            return 1;
        c = val;
    } while (c);

    return 0;
}
#endif

#ifndef atomic_inc_unless_negative
static inline int atomic_inc_unless_negative(atomic_t *p)
{
    int v, v1;
    for (v = 0; v >= 0; v = v1) {
        v1 = atomic_cmpxchg(p, v, v + 1);
        if (likely(v1 == v))
            return 1;
    }
    return 0;
}
#endif

#ifndef atomic_dec_unless_positive
static inline int atomic_dec_unless_positive(atomic_t *p)
{
    int v, v1;
    for (v = 0; v <= 0; v = v1) {
        v1 = atomic_cmpxchg(p, v, v - 1);
        if (likely(v1 == v))
            return 1;
    }
    return 0;
}
#endif

/*
 * atomic_dec_if_positive - decrement by 1 if old value positive
 * @v: pointer of type atomic_t
 *
 * The function returns the old value of *v minus 1, even if
 * the atomic variable, v, was not decremented.
 */
#ifndef atomic_dec_if_positive
static inline int atomic_dec_if_positive(atomic_t *v)
{
    int c, old, dec;
    c = atomic_read(v);
    for (;;) {
        dec = c - 1;
        if (unlikely(dec < 0))
            break;
        old = atomic_cmpxchg((v), c, dec);
        if (likely(old == c))
            break;
        c = old;
    }
    return dec;
}
#endif

#ifndef CONFIG_ARCH_HAS_ATOMIC_OR
static inline void atomic_or(int i, atomic_t *v)
{
    int old;
    int new;

    do {
        old = atomic_read(v);
        new = old | i;
    } while (atomic_cmpxchg(v, old, new) != old);
}
#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */

#include <asm-generic/atomic-long.h>
#ifdef CONFIG_GENERIC_ATOMIC64
#include <asm-generic/atomic64.h>
#endif
#endif /* _LINUX_ATOMIC_H */