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RE: Using __kuser_cmpxchg
On Mon, 19 Nov 2007, Boehm, Hans wrote:
> FWIW: The C++ atomics library that was recently voted into the C++
> working paper
> (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2427.html )
> allows "spurious" "compare_swap" failures, and returns both the read
> value, and
> whether or not the CAS succeeded. It would be nice if the kernel
> interface
> allowed that to be implemented as efficiently as possible.
Well, given that the version without spurious failure is 5 instructions
instead of 7 for the non-ARMv6 version, and 7 instead of 5 for the
ARMv6+ version, I don't think that going with the version without
spurious errors all the time will make much of a difference in
performance. In fact the non ARMv6 version which is actually the
important one (since optimized ARMv6 binaries may implement it inline
anyway) is now _more_ efficient than before.
Nicolas