Messages in this thread | | | Date | Thu, 6 Jan 2011 16:08:46 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [cpuops cmpxchg double V2 1/4] Generic support for this_cpu_cmpxchg_double |
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* Christoph Lameter (cl@linux.com) wrote: [...] > + * cmpxchg_double replaces two adjacent scalars at once. The first two > + * parameters are per cpu variables which have to be of the same size. > + * A truth value is returned to indicate success or > + * failure (since a double register result is difficult to handle). > + * There is very limited hardware support for these operations. So only certain > + * sizes may work.
What's the issue with returning the value read by cmpxchg_double in addition to the boolean ? "returning" it per se might be an issue, but you could add 2 more parameters to the macros that take the addresses of these outputs. Returning the values read by cmpxchg instead of just the boolean result helps removing the extra reads from cmpxchg loops, which is why I think it's a shame to just return the boolean result.
Thoughts ?
Mathieu
-- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com
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