Commit-ID: 8d4840e84871847ee1bae56a776907d08a9265f7 Gitweb: http://git.kernel.org/tip/8d4840e84871847ee1bae56a776907d08a9265f7 Author: David Howells <dhowells@xxxxxxxxxx> AuthorDate: Tue, 26 Apr 2016 10:22:06 -0700 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Thu, 28 Apr 2016 10:57:51 +0200 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 <dhowells@xxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: corbet@xxxxxxx Cc: dave@xxxxxxxxxxxx Cc: linux-doc@xxxxxxxxxxxxxxx Cc: will.deacon@xxxxxxx Link: http://lkml.kernel.org/r/1461691328-5429-2-git-send-email-paulmck@xxxxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- Documentation/memory-barriers.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index fb2dd35..8b11e54 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 ======== -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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