tree 4ac767de021735f8826ac849ac8a3795bd78ade5
parent 235963b2edc080b577000031b9ad75804dd83c88
author David Howells <dhowells@redhat.com> 1144734863 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1144761524 -0700

[PATCH] Fix memory barrier docs wrt atomic ops

Fix the memory barrier documentation to attempt to describe atomic ops
correctly.

atomic_t ops that return a value _do_ imply smp_mb() either side, and so
don't actually require smp_mb__*_atomic_*() special barriers.

Also explains why special barriers exist in addition to normal barriers.

Further fix the memory barrier documents to portray bitwise operation
memory barrier effects correctly following Nick Piggin's comments.

It makes the point that any atomic op that both modifies some state in
memory and returns information on that state implies memory barriers on
both sides.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>