While the {READ,WRITE}_ONCE() macros should be used in preference to
ACCESS_ONCE(), the circular buffer documentation uses the latter
exclusively.

To point people in the right direction, and as a step towards the
eventual removal of ACCESS_ONCE(), update the documentation to use
READ_ONCE(), as ACCESS_ONCE() is only used in a reader context in the
circular buffer documentation.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

This commit replaces full barriers by targeted use of load-acquire and
store-release.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Restore comments as suggested by David Howells. ]

The code sample in Documentation/circular-buffers.txt appears to have a
few ordering bugs.  This patch therefore applies the needed fixes.
Reported-by: NLech Fomicki <lfomicki@poczta.fm>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

Document the circular buffering capabilities available in Linux.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NRandy Dunlap <rdunlap@xenotime.net>
Reviewed-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>