Re: [cpuops cmpxchg double V2 1/4] Generic support forthis_cpu_cmpxchg_double

[Christoph Lameter]

On Fri, 21 Jan 2011, H. Peter Anvin wrote:

> We could do cmpxchg with a structure... the problem with a lon int type is that Cristoph ran into bugs with __int128 on 64 bits.

We also would need to be pass the structure by value (well its really a
variable but its like passing by value) in order to be similar to the
other this_cpu_ops

You'd want either

DEFINE_PERCPU(struct mycustomdoublestruct, percpu_dd)

this_cpu_cmpxchg_double(percpu_dd, oldword1, oldword2, newword1, newword2)

with the problem of type checking

or

this_cpu_cmpxchg_double(percpu_dd, old_dd, new_dd)

with the problem of 128 bit constants/structs passed by value.




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