Re: [PATCH -v2 14/33] locking,m68k: Implement atomic_fetch_{add,sub,and,or,xor}()

[Peter Zijlstra]

On Thu, Jun 16, 2016 at 02:53:09PM +0200, Andreas Schwab wrote:
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:

> > OK, care to elucidate? Clearly I need help reading this.
> 
> grep '2.*atomic_read'

Much thanks to your detailed answer I found yet another obscure inline
asm syntax 'feature'.

So the "2" input operand actually sets the value of "=&d" (tmp), how
creative...

I would find:

#define ATOMIC_OP_RETURN(op, c_op, asm_op)                              \
static inline int atomic_##op##_return(int i, atomic_t *v)              \
{                                                                       \
        int t, tmp = atomic_read(v);                                    \
                                                                        \
        __asm__ __volatile__(                                           \
                        "1:     movel %2,%1\n"                          \
                        "       " #asm_op "l %3,%1\n"                   \
                        "       casl %2,%1,%0\n"                        \
                        "       jne 1b"                                 \
                        : "+m" (*v), "=&d" (t), "+d" (tmp)              \
                        : "g" (i));                                     \
        return t;                                                       \
}

Much more obvious.

But you're right, it seems to be sorted. I'll queue a patch removing
that comment.

Thanks!