[9fans] waitfree

[erik quanstrom]

i've been thinking about ainc() and for the amd64 implementation,

        TEXT ainc(SB), 1, $-4                   /* int ainc(int*) */
                MOVL    $1, AX
                LOCK; XADDL AX, (RARG)
                ADDL    $1, AX
                RET

does anyone know if the architecture says this is wait-free?
this boils down to exactly how LOCK works, and i can't find
a good-enough definition.  i tend to think that it might not be.

- erik