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    Subject[RFC][PATCH 16/31] locking,mn10300: 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/mn10300/include/asm/atomic.h | 35 +++++++++++++++++++++++++++++++----
    1 file changed, 31 insertions(+), 4 deletions(-)

    --- a/arch/mn10300/include/asm/atomic.h
    +++ b/arch/mn10300/include/asm/atomic.h
    @@ -84,16 +84,43 @@ static inline int atomic_##op##_return(i
    return retval; \
    }

    -#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) \
    +{ \
    + int retval, status; \
    + \
    + asm volatile( \
    + "1: mov %4,(_AAR,%3) \n" \
    + " mov (_ADR,%3),%1 \n" \
    + " mov %1,%0 \n" \
    + " " #op " %5,%0 \n" \
    + " mov %0,(_ADR,%3) \n" \
    + " mov (_ADR,%3),%0 \n" /* flush */ \
    + " mov (_ASR,%3),%0 \n" \
    + " or %0,%0 \n" \
    + " bne 1b \n" \
    + : "=&r"(status), "=&r"(retval), "=m"(v->counter) \
    + : "a"(ATOMIC_OPS_BASE_ADDR), "r"(&v->counter), "r"(i) \
    + : "memory", "cc"); \
    + return retval; \
    +}
    +
    +#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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