atomicity of x86 bt/bts/btr/btc?

[Rick C. Hodgin]

> > They do not automatically lock the bus. They will lock the bus with the
> > explicit LOCK prefix, and BTS is typically used for an atomic read/write
> > operation.

> Thanks Rick.
> I'll go back to using them.
> I'm optimizing mainly for size.
> The comment should perhaps be amended.
> The "since they enforce atomic operation" part seems wrong.

Np.  For citation, see here (page 166).

   http://www.intel.com/Assets/PDF/manual/253666.pdf

- Rick