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Subject: Re: Atomic increment and get?
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2011/10/3 Lev Serebryakov <lev@freebsd.org>:
> =A0Is here atomic increment and get (or add and get) operation in
> =A0kernel? I cannot find one. Here is atomic_add_32(), but it doesn't
> =A0return result. And here is no atomic_add_64() on 32 bit system :(

See atomic_fetchadd_int.

Not all hardware has 64-bit atomic instructions available in 32-bit
mode so it's not machine-independent.  Generally, for this case (and
potentially for sub-32-bit atomic operations [1]) a lock is used.

[1] with masking and shifting 32-bit atomics can be used to set data
in an 8 or 16 bit variable; see a recent commit to sys/vm.

Cheers,
matthew