* Johannes Berg [off-list ref] wrote:

On Mon, 2017-10-23 at 21:07 +0000, Paul E. McKenney wrote:

quoted

From: Mark Rutland <mark.rutland@arm.com>

For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.

However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.

It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't pick up some uses, including those
in <linux/average.h>. As a preparatory step, this patch converts the
file to use {READ,WRITE}_ONCE() consistently.

At the same time, this patch addds missing includes necessary for
{READ,WRITE}_ONCE(), *BUG_ON*(), and ilog2().

----
virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Johannes Berg <redacted>

Reviewed-by: Johannes Berg <johannes@sipsolutions.net>

Thanks!

Let me know if you want me to apply this, since I seem to be the
average.h maintainer :-)

Would be nice to keep these patches together if possible, so that we can remove 
ACCESS_ONCE() - or at least add a build warning.

Thanks,

	Ingo