On Fri, 5 Sep 2014, Paul E. McKenney wrote:

On Fri, Sep 05, 2014 at 01:34:52PM -0700, H. Peter Anvin wrote:

quoted

On 09/05/2014 01:14 PM, Peter Hurley wrote:

quoted

Here's how I read the two statements.

First, the commit message:

"It [this commit] documents that CPUs [supported by the Linux kernel]
_must provide_ atomic one-byte and two-byte naturally aligned loads and stores."

Second, in the body of the document:

"The Linux kernel no longer supports pre-EV56 Alpha CPUs, because these
older CPUs _do not provide_ atomic one-byte and two-byte loads and stores."

Does this apply in general or only to SMP configurations?  I guess
non-SMP configurations would still have problems if interrupted in the
wrong place...

And preemption could cause problems, too.  So I believe that it needs
to be universal.

Well preemption is usually caused by an interrupt, except you have a
combined load and preempt instruction :)

Thanks,

	tglx