From 8d4840e84871847ee1bae56a776907d08a9265f7 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 26 Apr 2016 10:22:06 -0700 Subject: [PATCH] locking/Documentation: State purpose of memory-barriers.txt There has been some confusion about the purpose of memory-barriers.txt, so this commit adds a statement of purpose. Signed-off-by: David Howells Signed-off-by: Paul E. McKenney Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: corbet@lwn.net Cc: dave@stgolabs.net Cc: linux-doc@vger.kernel.org Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1461691328-5429-2-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- Documentation/memory-barriers.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index fb2dd35a823a..8b11e54238bf 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -19,6 +19,22 @@ in case of any doubt (and there are many) please ask. To repeat, this document is not a specification of what Linux expects from hardware. +The purpose of this document is twofold: + + (1) to specify the minimum functionality that one can rely on for any + particular barrier, and + + (2) to provide a guide as to how to use the barriers that are available. + +Note that an architecture can provide more than the minimum requirement +for any particular barrier, but if the architecure provides less than +that, that architecture is incorrect. + +Note also that it is possible that a barrier may be a no-op for an +architecture because the way that arch works renders an explicit barrier +unnecessary in that case. + + ======== CONTENTS ======== -- 2.39.5