Commit ac490f4d (Documentation: this_cpu_ops.txt: Update description
of this_cpu_ops) added lists of {__,}this_cpu operations, but these have
duplicate, parameter-less entries for {__,}this_cpu_add which don't
correspond to any implementation. No other operations have such
duplicate entries.

Given both are also listed with their full complement of arguments, the
empty forms are redundant and can be removed. This patch performs said
removal.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Update the description for per cpu operations to clarify use cases of
this_cpu operations and add considerations for remote access.
Signed-off-by: NPranith Kumar <bobby.prani@gmail.com>
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Document the rationale and the way to use this_cpu operations.

V2: Improved after feedback from Randy Dunlap

v3: Further spelling fixes from Randy.  Paragraphs refilled to 75
    column.

tj: Added .txt file extension to the document.
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NTejun Heo <tj@kernel.org>