cmpxchg_32.h

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/* 32-bit atomic xchg() and cmpxchg() definitions.
 *
 * Copyright (C) 1996 David S. Miller ([email protected])
 * Copyright (C) 2000 Anton Blanchard ([email protected])
 * Copyright (C) 2007 Kyle McMartin ([email protected])
 *
 * Additions by Keith M Wesolowski ([email protected]) based
 * on asm-parisc/atomic.h Copyright (C) 2000 Philipp Rumpf <[email protected]>.
 */

#ifndef __ARCH_SPARC_CMPXCHG__
#define __ARCH_SPARC_CMPXCHG__

static inline unsigned long xchg_u32(__volatile__ unsigned long *m, unsigned long val)
{
    __asm__ __volatile__("swap [%2], %0"
                 : "=&r" (val)
                 : "0" (val), "r" (m)
                 : "memory");
    return val;
}

extern void __xchg_called_with_bad_pointer(void);

static inline unsigned long __xchg(unsigned long x, __volatile__ void * ptr, int size)
{
    switch (size) {
    case 4:
        return xchg_u32(ptr, x);
    }
    __xchg_called_with_bad_pointer();
    return x;
}

#define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))

/* Emulate cmpxchg() the same way we emulate atomics,
 * by hashing the object address and indexing into an array
 * of spinlocks to get a bit of performance...
 *
 * See arch/sparc/lib/atomic32.c for implementation.
 *
 * Cribbed from <asm-parisc/atomic.h>
 */
#define __HAVE_ARCH_CMPXCHG 1

/* bug catcher for when unsupported size is used - won't link */
extern void __cmpxchg_called_with_bad_pointer(void);
/* we only need to support cmpxchg of a u32 on sparc */
extern unsigned long __cmpxchg_u32(volatile u32 *m, u32 old, u32 new_);

/* don't worry...optimizer will get rid of most of this */
static inline unsigned long
__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size)
{
    switch (size) {
    case 4:
        return __cmpxchg_u32((u32 *)ptr, (u32)old, (u32)new_);
    default:
        __cmpxchg_called_with_bad_pointer();
        break;
    }
    return old;
}

#define cmpxchg(ptr, o, n)                      \
({                                  \
    __typeof__(*(ptr)) _o_ = (o);                   \
    __typeof__(*(ptr)) _n_ = (n);                   \
    (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_,   \
            (unsigned long)_n_, sizeof(*(ptr)));        \
})

#include <asm-generic/cmpxchg-local.h>

/*
 * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
 * them available.
 */
#define cmpxchg_local(ptr, o, n)                           \
    ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
            (unsigned long)(n), sizeof(*(ptr))))
#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))

#endif /* __ARCH_SPARC_CMPXCHG__ */