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    Subject[RFC][PATCH 12/31] locking,m32r: Implement atomic_fetch_{add,sub,and,or,xor}()
    Implement FETCH-OP atomic primitives, these are very similar to the
    existing OP-RETURN primitives we already have, except they return the
    value of the atomic variable _before_ modification.

    This is especially useful for irreversible operations -- such as
    bitops (because it becomes impossible to reconstruct the state prior
    to modification).

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    arch/m32r/include/asm/atomic.h | 38 ++++++++++++++++++++++++++++++++++----
    1 file changed, 34 insertions(+), 4 deletions(-)

    --- a/arch/m32r/include/asm/atomic.h
    +++ b/arch/m32r/include/asm/atomic.h
    @@ -89,16 +89,46 @@ static __inline__ int atomic_##op##_retu
    return result; \
    }

    -#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op)
    +#define ATOMIC_FETCH_OP(op) \
    +static __inline__ int atomic_fetch_##op(int i, atomic_t *v) \
    +{ \
    + unsigned long flags; \
    + int result, val; \
    + \
    + local_irq_save(flags); \
    + __asm__ __volatile__ ( \
    + "# atomic_fetch_" #op " \n\t" \
    + DCACHE_CLEAR("%0", "r4", "%2") \
    + M32R_LOCK" %1, @%2; \n\t" \
    + "mv %0, %1 \n\t" \
    + #op " %1, %3; \n\t" \
    + M32R_UNLOCK" %1, @%2; \n\t" \
    + : "=&r" (result), "=&r" (val) \
    + : "r" (&v->counter), "r" (i) \
    + : "memory" \
    + __ATOMIC_CLOBBER \
    + ); \
    + local_irq_restore(flags); \
    + \
    + return result; \
    +}
    +
    +#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op) ATOMIC_FETCH_OP(op)

    ATOMIC_OPS(add)
    ATOMIC_OPS(sub)

    -ATOMIC_OP(and)
    -ATOMIC_OP(or)
    -ATOMIC_OP(xor)
    +#undef ATOMIC_OPS
    +#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op)
    +
    +#define atomic_fetch_or atomic_fetch_or
    +
    +ATOMIC_OPS(and)
    +ATOMIC_OPS(or)
    +ATOMIC_OPS(xor)

    #undef ATOMIC_OPS
    +#undef ATOMIC_FETCH_OP
    #undef ATOMIC_OP_RETURN
    #undef ATOMIC_OP


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