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    Subject[PATCH -v2 25/33] locking,xtensa: 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/xtensa/include/asm/atomic.h | 54 ++++++++++++++++++++++++++++++++++++---
    1 file changed, 50 insertions(+), 4 deletions(-)

    --- a/arch/xtensa/include/asm/atomic.h
    +++ b/arch/xtensa/include/asm/atomic.h
    @@ -98,6 +98,26 @@ static inline int atomic_##op##_return(i
    return result; \
    }

    +#define ATOMIC_FETCH_OP(op) \
    +static inline int atomic_fetch_##op(int i, atomic_t * v) \
    +{ \
    + unsigned long tmp; \
    + int result; \
    + \
    + __asm__ __volatile__( \
    + "1: l32i %1, %3, 0\n" \
    + " wsr %1, scompare1\n" \
    + " " #op " %0, %1, %2\n" \
    + " s32c1i %0, %3, 0\n" \
    + " bne %0, %1, 1b\n" \
    + : "=&a" (result), "=&a" (tmp) \
    + : "a" (i), "a" (v) \
    + : "memory" \
    + ); \
    + \
    + return result; \
    +}
    +
    #else /* XCHAL_HAVE_S32C1I */

    #define ATOMIC_OP(op) \
    @@ -138,18 +158,44 @@ static inline int atomic_##op##_return(i
    return vval; \
    }

    +#define ATOMIC_FETCH_OP(op) \
    +static inline int atomic_fetch_##op(int i, atomic_t * v) \
    +{ \
    + unsigned int tmp, vval; \
    + \
    + __asm__ __volatile__( \
    + " rsil a15,"__stringify(TOPLEVEL)"\n" \
    + " l32i %0, %3, 0\n" \
    + " " #op " %1, %0, %2\n" \
    + " s32i %1, %3, 0\n" \
    + " wsr a15, ps\n" \
    + " rsync\n" \
    + : "=&a" (vval), "=&a" (tmp) \
    + : "a" (i), "a" (v) \
    + : "a15", "memory" \
    + ); \
    + \
    + return vval; \
    +}
    +
    #endif /* XCHAL_HAVE_S32C1I */

    -#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op)
    +#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op) ATOMIC_OP_RETURN(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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